RE: EN60950-1 Table 5B error?

[emc-p...@ieee.org]

Thanks David and Don.  This makes sense now.

Jim Eichner, P.Eng. 
Compliance Engineering Manager
Xantrex Technology Inc. 
phone: (604) 422-2546 
fax: (604) 420-1591 
e-mail: jim.eich...@xantrex.com 
web: www.xantrex.com 
Confidentiality Notice: This email message, including any attachments,
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From: emc-p...@ieee.org  On Behalf Of David Gelfand
Sent: Wednesday, June 14, 2006 4:59 AM
To: emc-p...@ieee.org
Subject: RE: EN60950-1 Table 5B error?

Jim,

I believe the table is ok.  Table 2G note 1 points to clause 5.3.4,
requirements for functional insulation.  If you don't meet clearance and
creepage distance requirements for functional insulation, you can choose
500V electric strength test as alternate option.  Electric strength
requirements do not apply to components bridging functional isolation.  

Regards,

David.

David Gelfand, P.E.
Product Integrity Engineer
Mitec Telecom Inc
9000 Trans-Canada Highway
Pointe-Claire QC
Canada H9R 5Z8
514 694 9000 x2262



From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Jim
Eichner
Sent: 13 juin 2006 18:57
To: emc-p...@ieee.org
Subject: EN60950-1 Table 5B error?

Referring to the 2nd last column ("between independent secondary
circuits", working voltage U< 42.4Vpk), why would Functional insulation
require a 500V test but Basic/Supplemental/Reinforced have no test?  Is
this table wrong?

For components (optocoupler, SMT transformer) crossing a Functional
isolation boundary between an SELV circuit and another SELV circuit (an
ethernet circuit in this case), do I need to specify electric strength
requirements?  

Thanks,

Jim Eichner, P.Eng. 
Compliance Engineering Manager
Xantrex Technology Inc. 
e-mail: jim.eich...@xantrex.com
web: www.xantrex.com
Any opinions expressed are those of my invisible friend.
Confidentiality Notice: This email message, including any attachments,
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RE: EN60950-1 Table 5B error?

[emc-p...@ieee.org]

Jim,

The table is not wrong.  The working voltages in that column are
non-hazardous, so basic, supplementary and reinforced insulation do not
apply.  The application for that column would be the use of 5.3.4 (b) for
evaluating SELV or ELV functional insulation.

Regards,

Don Gies, N.C.E
Senior Product Compliance Engineer
Lucent Technologies - Global Product Compliance Laboratory
Holmdel, NJ 07733 USA


From: Jim Eichner [mailto:jim.eich...@xantrex.com] 
Sent: Tuesday, June 13, 2006 6:57 PM
To: EMC-PSTC@listserv.ieee.org
Subject: EN60950-1 Table 5B error?

Referring to the 2nd last column ("between independent secondary
circuits", working voltage U< 42.4Vpk), why would Functional insulation
require a 500V test but Basic/Supplemental/Reinforced have no test?  Is
this table wrong?

For components (optocoupler, SMT transformer) crossing a Functional
isolation boundary between an SELV circuit and another SELV circuit (an
ethernet circuit in this case), do I need to specify electric strength
requirements?  

Thanks,

Jim Eichner, P.Eng. 
Compliance Engineering Manager
Xantrex Technology Inc. 
e-mail: jim.eich...@xantrex.com 
web: www.xantrex.com 
Any opinions expressed are those of my invisible friend.
Confidentiality Notice: This email message, including any attachments,
is for the sole use of the intended recipient(s) and may contain
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RE: EN60950-1 Table 5B error?

[emc-p...@ieee.org]

Jim,

I believe the table is ok.  Table 2G note 1 points to clause 5.3.4,
requirements for functional insulation.  If you don't meet clearance and
creepage distance requirements for functional insulation, you can choose
500V electric strength test as alternate option.  Electric strength
requirements do not apply to components bridging functional isolation.  

Regards,

David.

David Gelfand, P.E.
Product Integrity Engineer
Mitec Telecom Inc
9000 Trans-Canada Highway
Pointe-Claire QC 
Canada H9R 5Z8
514 694 9000 x2262



From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Jim
Eichner
Sent: 13 juin 2006 18:57
To: emc-p...@ieee.org
Subject: EN60950-1 Table 5B error?

Referring to the 2nd last column ("between independent secondary
circuits", working voltage U< 42.4Vpk), why would Functional insulation
require a 500V test but Basic/Supplemental/Reinforced have no test?  Is
this table wrong?

For components (optocoupler, SMT transformer) crossing a Functional
isolation boundary between an SELV circuit and another SELV circuit (an
ethernet circuit in this case), do I need to specify electric strength
requirements?  

Thanks,

Jim Eichner, P.Eng. 
Compliance Engineering Manager
Xantrex Technology Inc. 
e-mail: jim.eich...@xantrex.com
web: www.xantrex.com
Any opinions expressed are those of my invisible friend.
Confidentiality Notice: This email message, including any attachments,
is for the sole use of the intended recipient(s) and may contain
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disclosure or distribution is prohibited. If you are not the intended
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copies of the original message.

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Re: EN60950 2nd edition expiring

[owner-emc-p...@listserv.ieee.org]

> Can you advise me if products made this year under the 2nd edition can still
be sold in
Europe in 2005?

Gary,

The date of cessation of presumption of conformity of the 2nd edition is
1/1/05, so presumption
of conformity can not be provided by this standard and the products can not be
put on the
market after Dec. 31, 2004. But there is an alternative path: asses your
product to determine
if you can provide evidence of conformity with the essential requirements of
the LVD (see the
LVD for details).

Regards,

John Radomski
Principal Engineer
Schneider Automation


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Re: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Here is a link to one vendor's IEC 309 type plugs and sockets. Scroll 
down toward the bottom for photos.

http://www.schneider-electric.co.th/product/powerplug.htm

Scott Douglas, NCE



Richard Hughes wrote:

>Joe,
>
>You asked...
>
>Joe Randolph wrote:
>
> > Hi Richard:
> >
>
> >
> > I do have one remaining question.  You mention that EN60309 describes
> > pluggable Type B sockets.  I do not have a copy of EN60309.  It is true
> > that the standard AC mains plugs commonly used on home and office ITE
> > products are completely incompatible with the ones defined in EN60309?
> > I would just like to know if there is any opportunity for a manufacturer
> > to argue that the plug on their standard office ITE product is actually
> > intended for a Type B socket.
> >
> > Thanks again for your help with sorting all this out.
> >
>
>REH> IEC/EN 60309 is a standard that covers industrial mains plugs, 
>mains sockets and industrial couplers.  If you ever see one of the plugs 
>or sockets you would understand why it is impossible to fit an ordinary 
>domestic plug (certainly and European or US plug that I'm familiar with) 
>by accident, or even foreseeable misuse, into an IEC/EN 60309 socket. 
>So there is no opportunity for a manufacturer to argue that the domestic 
>plug fitted to the cord of their standard office ICT product is actually 
>intended for a Type B socket
>
>
> >
> > Joe Randolph
> > Telecom Design Consultant
> > Randolph Telecom, Inc.
> > 781-721-2848 (USA)
> > j...@randolph-telecom.com
> > http://www.randolph-telecom.com
> >
> >
>
>
>---
>This message is from the IEEE EMC Society Product Safety
>Technical Committee emc-pstc discussion list.
>
>Visit our web site at:  http://www.ieee-pses.org/
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>
>
>  
>




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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Joe,

You asked...

Joe Randolph wrote:

 > Hi Richard:
 >

 >
 > I do have one remaining question.  You mention that EN60309 describes
 > pluggable Type B sockets.  I do not have a copy of EN60309.  It is true
 > that the standard AC mains plugs commonly used on home and office ITE
 > products are completely incompatible with the ones defined in EN60309?
 > I would just like to know if there is any opportunity for a manufacturer
 > to argue that the plug on their standard office ITE product is actually
 > intended for a Type B socket.
 >
 > Thanks again for your help with sorting all this out.
 >

REH> IEC/EN 60309 is a standard that covers industrial mains plugs, 
mains sockets and industrial couplers.  If you ever see one of the plugs 
or sockets you would understand why it is impossible to fit an ordinary 
domestic plug (certainly and European or US plug that I'm familiar with) 
by accident, or even foreseeable misuse, into an IEC/EN 60309 socket. 
So there is no opportunity for a manufacturer to argue that the domestic 
plug fitted to the cord of their standard office ICT product is actually 
intended for a Type B socket


 >
 > Joe Randolph
 > Telecom Design Consultant
 > Randolph Telecom, Inc.
 > 781-721-2848 (USA)
 > j...@randolph-telecom.com
 > http://www.randolph-telecom.com
 >
 >



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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Hi Richard:

Thanks for yet another detailed description regarding aspects of this
confusing topic.

My conclusion from all this discussion is that the only practical
difference between the 6.1.2.2 text in the main body of EN 60950-1 and
the text in Annex ZB is that for Finland, Norway, and Sweden, equipment
that uses a permanently connected earthing conductor must be installed
by a service person.  The text in the main body leaves open the
possibility that the protective earthing conductor could be installed by
the user.  I don't know why they couldn't state the difference more
simply.

A related conclusion is that for "typical" office equipment, surge
protectors from tip/ring to ground must have a minimum breakover of 400
volts in Finland, Norway, and Sweden unless the equipment is intended to
be installed by a service person.

I do have one remaining question.  You mention that EN60309 describes
pluggable Type B sockets.  I do not have a copy of EN60309.  It is true
that the standard AC mains plugs commonly used on home and office ITE
products are completely incompatible with the ones defined in EN60309?
I would just like to know if there is any opportunity for a manufacturer
to argue that the plug on their standard office ITE product is actually
intended for a Type B socket.

Thanks again for your help with sorting all this out.
 
 
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com


> -Original Message-
> From: owner-emc-p...@majordomo.ieee.org 
> [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Richard Hughes
> Sent: Friday, January 09, 2004 9:47 AM
> To: Joe Randolph
> Cc: emc-p...@majordomo.ieee.org
> Subject: RE: EN60950-1,TNV to Earth Insulation
> 
> 
> 
> Joe,
> 
> Following fast on the heals of my earlier reply, you can perhaps 
> understand that equipment that is professionally installed is 
> expected 
> to be earthed if required (otherwise the installer could hardly be 
> called 'professional'!).
> 
> Similarly,  it is expected that an industrial socket to EN60309 
> (pluggable Type B) will be installed so that its earth connection is 
> connected to the building's earth.
> 
> Point 3 is for the Central Office of telecoms centres.  
> Again, in such 
> premises it is expected that a 'proper' earth connection will be 
> available.  For equipment powered from station office 
> batteries, this is 
>   generally a sub-set of 1.
> 
> Point 4 is not applicable in Europe, as can be seen by looking at EN 
> 60950-1 clause 6.1.2.2, where you will see that it has been 
> removed as a 
> Common Modification. Basically, it is considered that a label on the 
> equipment telling the user to get the equipment 
> professionally installed 
> does not provide an adequate degree of safety (due to the 
> likelihood of 
> such a notice being disregarded).
> 
> I hope that this is now the end of this topic, but if not I'm 
> more than 
> happy to provide PAID consultation!!!
> 
> Regards,
> 
> Richard Hughes
> www.safetyanswers.ltd.uk
> 
> 
> 
> Joe Randolph wrote:
> 
>  >
>  > In a posting dated 1/8/2004, I wrote:
>  >
>  > > Now I go to Annex ZB and look at the deviations to 
> clause  > > 6.1.2.2 for Finland, Norway, and Sweden.  The 
> exclusions  > > described here are much more restrictive, 
> limited to  > > permanently connected equipment or pluggable 
> equipment type  > > B, used in restricted access locations 
> where equipotential  > > bonding has been applied.  In other 
> words, a telephone  > > central office or *maybe* the main 
> telephone closet in an  > > office building.  Certainly, no 
> stretch of the imagination  > > would have this clause 
> include the typical office environment.  >  >  > Hello All:  
> >  > Okay, I re-read the wording of the Annex ZB deviation to 
> clause 6.1.2.2  > of EN 60950-1, and I think I have developed 
> a partial answer to my own  > question.  I see that I missed 
> the word "and" in one place and perhaps  > misinterpreted the 
> meaning of "and" in a second place.  After reading  > the 
> clause carefully several times, I think it is saying that 
> exclusions  > are available for four separate cases:  >  > 1) 
> Permanently connected equipment.  >  > 2) Pluggable equipment 
> Type B.  >  > 3) Equipment used in a restricted access 
> location that has equipotential  > bonding.  >  > 4) 
> Equipment that has provisions for a permanently connected 
> protective  > earthing conductor and is provided with 
> instructions for installation 

RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

In a message dated 1/9/2004, Richard Hughes writes:

> I hope that I have explained why the insulation is for a Primary
Circuit 
> rather than for a Secondary Circuit (as could be expected because a
TNV 
> Circuit is a Secondary Circuit).


Hi Richard:

Thanks for your detailed description.  As it turns out, I have heard
variations of this rationale before.  In fact, what we now think of as a
"Nordic" requirement used to appear in the UK safety standard BS 6301
back in the 1980s.  A fellow at BT offered a similar (but not identical)
rationale when I inquired about it at the time.  The same requirement
was included in the initial "harmonized" telecom safety standard EN
41003, and at least one edition of that standard actually contained an
explanatory note that summarized the rationale.

However, I think the discussion has drifted from the original question,
which had to do with interpreting what the latest requirements in EN
60950-1 call for.  Under the latest version of Annex ZB there is no need
to debate whether the supplementary insulation should be for a primary
circuit or a secondary circuit, because there is no reference whatsoever
to supplementary insulation.  All that remains is a list of specific
requirements on solid insulation.

There is only one remaining place in the standard where it is necessary
to decide whether the TNV insulation is for a primary circuit or a
secondary circuit.  That occurs in clause 2.3.2 where there is a
reference to basic insulation.  In this case the applicable requirements
are those for a secondary circuit.

As Ron Pickard noted in an earlier posting, the current edition still
leaves room for people to have debates (as they have for years) about
the assigned working voltage for the basic insulation referenced in
clause 2.3.2.  I avoided commenting on this earlier because I did not
want to open another can of worms.  

For what it's worth, the conservative interpretation that I have been
persuaded to use says the working voltage for a generic, unspecified
TNV-3 PSTN line is 120 volts (max TNV) plus the SELV voltage on the
other side of the barrier.  This yields a range of 120 to 180 volts,
depending on the characteristics of the SELV circuit.  So, for
compliance with the basic insulation requirement in clause 2.3.2, we
have a working voltage (subject to debate) and we know that the
applicable tables are those for a secondary circuit (not subject to
debate, as far as I know).



Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com



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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Joe,

Following fast on the heals of my earlier reply, you can perhaps 
understand that equipment that is professionally installed is expected 
to be earthed if required (otherwise the installer could hardly be 
called 'professional'!).

Similarly,  it is expected that an industrial socket to EN60309 
(pluggable Type B) will be installed so that its earth connection is 
connected to the building's earth.

Point 3 is for the Central Office of telecoms centres.  Again, in such 
premises it is expected that a 'proper' earth connection will be 
available.  For equipment powered from station office batteries, this is 
  generally a sub-set of 1.

Point 4 is not applicable in Europe, as can be seen by looking at EN 
60950-1 clause 6.1.2.2, where you will see that it has been removed as a 
Common Modification. Basically, it is considered that a label on the 
equipment telling the user to get the equipment professionally installed 
does not provide an adequate degree of safety (due to the likelihood of 
such a notice being disregarded).

I hope that this is now the end of this topic, but if not I'm more than 
happy to provide PAID consultation!!!

Regards,

Richard Hughes
www.safetyanswers.ltd.uk



Joe Randolph wrote:

 >
 > In a posting dated 1/8/2004, I wrote:
 >
 > > Now I go to Annex ZB and look at the deviations to clause
 > > 6.1.2.2 for Finland, Norway, and Sweden.  The exclusions
 > > described here are much more restrictive, limited to
 > > permanently connected equipment or pluggable equipment type
 > > B, used in restricted access locations where equipotential
 > > bonding has been applied.  In other words, a telephone
 > > central office or *maybe* the main telephone closet in an
 > > office building.  Certainly, no stretch of the imagination
 > > would have this clause include the typical office environment.
 >
 >
 > Hello All:
 >
 > Okay, I re-read the wording of the Annex ZB deviation to clause 6.1.2.2
 > of EN 60950-1, and I think I have developed a partial answer to my own
 > question.  I see that I missed the word "and" in one place and perhaps
 > misinterpreted the meaning of "and" in a second place.  After reading
 > the clause carefully several times, I think it is saying that exclusions
 > are available for four separate cases:
 >
 > 1) Permanently connected equipment.
 >
 > 2) Pluggable equipment Type B.
 >
 > 3) Equipment used in a restricted access location that has equipotential
 > bonding.
 >
 > 4) Equipment that has provisions for a permanently connected protective
 > earthing conductor and is provided with instructions for installation of
 > that conductor by a service person.
 >
 >
 > In the wording of Annex ZB, note that the "and" between cases 3 and 4
 > could be interpreted to be merging them into a single case, rather than
 > establishing case 4 as a standalone case.
 >
 > So, the liberal interpretation is that case 4 is a viable, standalone
 > option, similar to the 6.1.2.2 text in the main body of the standard
 > except for the specific reference to having a service person install the
 > ground conductor.  Even with the reference to the service person, this
 > case provides enough wiggle room to allow the equipment to be used in a
 > normal office environment.
 >
 > The conservative interpretation merges cases 3 and 4 into a single case
 > and pretty much excludes the normal office environment if the AC mains
 > connector is pluggable Type A.
 >
 > I'm still interested to know what other list members think this means
 > for the case I described in my earlier posting.
 >
 >
 >
 > Joe Randolph
 > Telecom Design Consultant
 > Randolph Telecom, Inc.
 > 781-721-2848 (USA)
 > j...@randolph-telecom.com
 > http://www.randolph-telecom.com
 >
 >
 >
 > ---
 > This message is from the IEEE EMC Society Product Safety
 > Technical Committee emc-pstc discussion list.
 >
 > Visit our web site at:  http://www.ieee-pses.org/
 >
 > To cancel your subscription, send mail to:
 >  majord...@ieee.org
 > with the single line:
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 >
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 >  Jim Bacher: j.bac...@ieee.org
 >
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 >




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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Joe,

So you want to know more about the Nordic deviations regarding EN 
60950-1, well sit yourself down and get a mug of coffee as I explain the 
reasons behind these deviations…

In Scandinavia (we are told in the IEC by representatives from the 
countries mentioned in the deviations) it is common to find socket 
outlets that have an earth connection that is in fact not connected. 
Now, it has also been discussed that other countries have this situation 
too, but they have chosen not to adopt the same deviations as the 
Scandinavian countries [if you consider that this applies in your 
country and think that something should be done about it, then please 
contact your national committee].

Most equipment only has Basic Insulation between the Primary Circuit and 
Protective Earth and also has Y capacitors connected across this Basic 
Insulation.  Now, you may think that this situation is questionable from 
a safety perspective, but it is referred to as a Class 0 installation. 
In the vicinity of the equipment everything is (supposed to be) earth 
free and so if you were to bridge between a such a part and a part that 
is connected to the mains by Y caps (i.e. anything connected to the 
Protective Earth connection of most ICT equipment) then no current (or 
only a small, depending on the insulation resistance) would flow and so 
you would not get an electric shock.

Now consider a telecommunications system.  It can, and is, touched by 
network engineers far removed from the customer’s premises.  These 
engineers can be earthed and so it is important that they are 
effectively protected from parts that are only separated from the 
Primary Circuit by Basic Insulation.  Following the classic approach, it 
should now be easy to see where the original requirement for 
Supplementary Insulation came from and why this was for a Primary 
Circuit and not a Secondary Circuit.

Given that the ac mains supply has a tolerance of 10% and the peak of 
the ac mains is 1.414 times the rms value, we have a combined 
magnification factor of 1.5554, or 1.6 to be a bit on the safe side.  A 
device, whether it be a gas tube or a semiconductor device, rated 300Vdc 
will break down when the mains is applied to it and so it will not 
protect the network engineer in the situation as described above.  Of 
course, all devices have a tolerance and that is why the standard 
defines the MINIMUM value: it is for the manufacturer to choose a rated 
value and tolerance that will not break down when the mains is applied 
to it.

I hope that I have explained why the insulation is for a Primary Circuit 
rather than for a Secondary Circuit (as could be expected because a TNV 
Circuit is a Secondary Circuit).

Regards,

Richard Hughes

Safety Answers Limited
www.safetyanswers.ltd.uk






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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Hi Joe,
If you have unbalanced protection only, i.e. a surge protector between tip
and ring, then the conduction voltage for the device can be down as low as
270V, which is dictataed by the functional requirements of the  circuit
rather than safety. For functional reasons, sometimes you have to have a
ground reference on the interface, so you have to usea balanced protection
scheme. If you have balanced protection, ie a surge protector between tip
and ground (T-G) , ring and ground (R-G), and tip to ring(T-R), AND you
don't have a permanently connected protective earth, then the T-G, and R-G
surge devices have to be 1.6 times the rated voltage, i.e. for 240V rated
the conduction voltage must be 400V. Obviously the T-R device does not have
to meet that requirement. As a bonus it turned out that the 400V devices
were the same price as the 300V devices. (Note: the surge protectors I am
talking about are semiconductor type, not gas discharge).

Regards

Doug



  

  "Joe Randolph"  

  , 
  com>  
 
   
  Sent by: cc:

  owner-emc-pstc@majordo   Subject:  RE: EN60950-1,TNV
to Earth Insulation 
  mo.ieee.org 

  

  

  01/09/04 01:50 AM   

  Please respond to "Joe  

  Randolph"   

  

  





In a message dated 1/8/2004, Peter Merguerian writes:

> There should be no problem to find min. 400 V surge protectors - they are
readily available

> I am sure that the fax, modems, PBXs out there which have been certified
are mounted with
> surge protectors with a breakover voltage of 1.6 Vrated of the equipment.


Hi Peter:

Actually, in the cases I referenced, the protection devices were in the
range of 300 volts.  This seems to be fairly common.  I think the typical
reason is that the designers were simply not aware of the 1.6x requirement,
so they chose breakdown voltages based on the maximum ringing voltage.

I know it is easy to get gas tubes with minimum breakdowns of over 400
volts, but semiconductor devices such as sidactors are not typically
available with such high voltage ratings.  I have seen several designs that
used a 3-terminal sidactor with a minimum breakdown in the range of 270
volts.

In my own designs, I avoid putting protection devices from TNV-3 to ground
unless it is absolutely necessary, such as on a FXS-type feed circuit that
must supply ground referenced DC feed and ringing.  For the typical
FXO-type interfaces used in terminal devices like modems and fax machines,
I only put breakdown devices across tip/ring, and then I rely on a good
isolation barrier for protection from surges between tip/ring and ground.

The reason for my original posting was simply that I am curious about all
the products I have seen that had sub-400 volt protection devices from
tip/ring to ground and also had no provisions for a permanent earth
connection.  Either these designs are slipping through the safety approval
process by mistake, or I am misinterpreting clause 6.1.2.1.

It sounds as though you would agree that any such designs must have slipped
through the safety approval process by mistake.


Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com






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Technical Committee emc-pstc discussion list.

Visit our web site at:  http://www.ieee-pses.or

RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

In a message dated 1/8/2004, Peter Merguerian writes: 
 
> There should be no problem to find min. 400 V surge protectors - they are
readily available 
 
> I am sure that the fax, modems, PBXs out there which have been certified are
mounted with 
> surge protectors with a breakover voltage of 1.6 Vrated of the equipment. 
 
 
Hi Peter:
 
Actually, in the cases I referenced, the protection devices were in the range
of 300 volts.  This seems to be fairly common.  I think the typical reason is
that the designers were simply not aware of the 1.6x requirement, so they
chose breakdown voltages based on the maximum ringing voltage.
 
I know it is easy to get gas tubes with minimum breakdowns of over 400 volts,
but semiconductor devices such as sidactors are not typically available with
such high voltage ratings.  I have seen several designs that used a 3-terminal
sidactor with a minimum breakdown in the range of 270 volts.
 
In my own designs, I avoid putting protection devices from TNV-3 to ground
unless it is absolutely necessary, such as on a FXS-type feed circuit that
must supply ground referenced DC feed and ringing.  For the typical FXO-type
interfaces used in terminal devices like modems and fax machines, I only put
breakdown devices across tip/ring, and then I rely on a good isolation barrier
for protection from surges between tip/ring and ground.
 
The reason for my original posting was simply that I am curious about all the
products I have seen that had sub-400 volt protection devices from tip/ring to
ground and also had no provisions for a permanent earth connection.  Either
these designs are slipping through the safety approval process by mistake, or
I am misinterpreting clause 6.1.2.1.
 
It sounds as though you would agree that any such designs must have slipped
through the safety approval process by mistake.
 
 
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com

RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Joe,
 
There should be no problem to find min. 400 V surge protectors - they are
readily available. I recently had this problem with a manufacturer of an
office appliance and they were able to find a similar surge protector rated
for the higher breakover voltage. 
 
If you need to locate a source for min. 400 V breakover surge protectors,
please let me know. 
 
I am sure that the fax, modems, PBXs out there which have been certified are
mounted with surge protectors with a breakover voltage of 1.6 Vrated of the
equipment. 
 
 
Best Regards,
 
Peter

Joe Randolph  wrote:


Hello All:

While we are on the subject of TNV-to-earth insulation, I would like to
pose a related question regarding clause 6.1.2.1 in EN 60950-1 and the
deviations in Annex ZB for Finland, Sweden, and Norway. This question
relates to the requirement that "surge suppressors that bridge the
insulation shall have a minimum breakover voltage of 1.6 times the rated
voltage.". 

Suppose I have a piece of office equipment that is powered from the AC
mains and has a rated voltage of 250 VRMS. The equipment also has a
connection to a TNV-3 phone line. It uses a 3-wire AC mains plug that
includes an earth ground. 

Inside the equipment, the surge protection on the TNV-3 phone line
includes two 300 volt surge protectors, connected from tip to ground and
>from ring to ground (there is a third surge protector connected across
tip! and ring, but that is incidental to the question at hand). I have
seen this type of construction many times, and I believe it is widely
used in the industry.

Now, if I evaluate this construction for compliance with clause 6.1.2.1,
I quickly conclude that the two surge protectors connected tip-to-ground
and ring-to-ground must have a minimum breakover voltage of no less than
(1.6)x(250) = 400 volts. 

Okay, this looks like a problem, but the exclusions in clause 6.1.2.2
leave some wiggle room. This particular piece of office equipment is
not permanently connected, nor is it installed by a service person.
However, it is possible to equip it with provisions for a permanent
earthing conductor and then provide instructions for the installation of
that conductor. Never mind how many users will actually read the
instructions

Now I go to Annex ZB and look at the deviations to clause 6.1.2.2 for
Finland, Norway, and Sweden. The exclusions described here are much
more restrictive, limited to permanently connected equipment or
pluggable equipment type B, used in restricted access locations where
equipotential bonding has been applied. In other words, a telephone
central office or *maybe* the main telephone closet in an office
building. Certainly, no stretch of the imagination would have this
clause include the typical office environment.

So, does this equipment fail to comply with EN 60950-1 for use in
Finland, Norway, and Sweden? It appears to me that it fails to comply,
but I can tell you there is a lot of product out there that meets this
description. Think modems, fax machines, and small PBXs.

I would like to hear what others in the group think. Am I missing
something here?


Thanks,

Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com



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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

In a posting dated 1/8/2004, I wrote:

> Now I go to Annex ZB and look at the deviations to clause 
> 6.1.2.2 for Finland, Norway, and Sweden.  The exclusions 
> described here are much more restrictive, limited to 
> permanently connected equipment or pluggable equipment type 
> B, used in restricted access locations where equipotential 
> bonding has been applied.  In other words, a telephone 
> central office or *maybe* the main telephone closet in an 
> office building.  Certainly, no stretch of the imagination 
> would have this clause include the typical office environment.


Hello All:

Okay, I re-read the wording of the Annex ZB deviation to clause 6.1.2.2
of EN 60950-1, and I think I have developed a partial answer to my own
question.  I see that I missed the word "and" in one place and perhaps
misinterpreted the meaning of "and" in a second place.  After reading
the clause carefully several times, I think it is saying that exclusions
are available for four separate cases:

1) Permanently connected equipment.

2) Pluggable equipment Type B.

3) Equipment used in a restricted access location that has equipotential
bonding.

4) Equipment that has provisions for a permanently connected protective
earthing conductor and is provided with instructions for installation of
that conductor by a service person.


In the wording of Annex ZB, note that the "and" between cases 3 and 4
could be interpreted to be merging them into a single case, rather than
establishing case 4 as a standalone case.

So, the liberal interpretation is that case 4 is a viable, standalone
option, similar to the 6.1.2.2 text in the main body of the standard
except for the specific reference to having a service person install the
ground conductor.  Even with the reference to the service person, this
case provides enough wiggle room to allow the equipment to be used in a
normal office environment.

The conservative interpretation merges cases 3 and 4 into a single case
and pretty much excludes the normal office environment if the AC mains
connector is pluggable Type A.

I'm still interested to know what other list members think this means
for the case I described in my earlier posting.


 
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com




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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Hello All:

While we are on the subject of TNV-to-earth insulation, I would like to
pose a related question regarding clause 6.1.2.1 in EN 60950-1 and the
deviations in Annex ZB for Finland, Sweden, and Norway.  This question
relates to the requirement that "surge suppressors that bridge the
insulation shall have a minimum breakover voltage of 1.6 times the rated
voltage.".  

Suppose I have a piece of office equipment that is powered from the AC
mains and has a rated voltage of 250 VRMS.  The equipment also has a
connection to a TNV-3 phone line.  It uses a 3-wire AC mains plug that
includes an earth ground.  

Inside the equipment, the surge protection on the TNV-3 phone line
includes two 300 volt surge protectors, connected from tip to ground and
>from ring to ground (there is a third surge protector connected across
tip and ring, but that is incidental to the question at hand).  I have
seen this type of construction many times, and I believe it is widely
used in the industry.

Now, if I evaluate this construction for compliance with clause 6.1.2.1,
I quickly conclude that the two surge protectors connected tip-to-ground
and ring-to-ground must have a minimum breakover voltage of no less than
(1.6)x(250) = 400 volts.  

Okay, this looks like a problem, but the exclusions in clause 6.1.2.2
leave some wiggle room.  This particular piece of office equipment is
not permanently connected, nor is it installed by a service person.
However, it is possible to equip it with provisions for a permanent
earthing conductor and then provide instructions for the installation of
that conductor.  Never mind how many users will actually read the
instructions

Now I go to Annex ZB and look at the deviations to clause 6.1.2.2 for
Finland, Norway, and Sweden.  The exclusions described here are much
more restrictive, limited to permanently connected equipment or
pluggable equipment type B, used in restricted access locations where
equipotential bonding has been applied.  In other words, a telephone
central office or *maybe* the main telephone closet in an office
building.  Certainly, no stretch of the imagination would have this
clause include the typical office environment.

So, does this equipment fail to comply with EN 60950-1 for use in
Finland, Norway, and Sweden?  It appears to me that it fails to comply,
but I can tell you there is a lot of product out there that meets this
description.  Think modems, fax machines, and small PBXs.

I would like to hear what others in the group think.  Am I missing
something here?


Thanks,

Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com



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RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Richard,

>REH> It is my belief that the dielectric withstand test is that required
>for basic insulation for a PRIMARY circuit, not a SECONDARY circuit -
>although I agree the requirement is not as clear as it could be.
>REH> If you look at   Annex ZB it tells you to "add the following text
>between the first and second paragraph", part of the text being "each of
>which shall pass the electric strength test below" and the second para
>has the text "insulation shall have a minimum d.c. sparkover voltage of
>1,6 times the RATED VOLTAGE or 1,6 times the upper voltage of the RATED
>VOLTAGE RANGE of the equipment"

The "1.6 x RATED VOLTAGE" requirement goes back to at least IEC950:1991
(6.3.3.1) where basic
insulation was required and I presume for a secondary circuit as it doesn't
specifically state that.
The primary circuit requirement came from Annex ZB (6.2.1.2), which was
specifically stated,
therefore leading one to believe that it would a secondary circuit normally.
Unfortunately, it is
not stated in EN60950-1 one way or the other, so I believe that it will be
left to interpretation
(and many a heated argument, I suspect). Actually, if a primary circuit is
applied, then this change
in the standard is all a matter of semantics (a rose by any other name is
still a rose). So,
treating it as a primary circuit, technically nothing changes from earlier
standards (its just
described differently). But, if its treated as a secondary circuit, creepages
and clearances will
likely be reduced.

But, is it for a secondary circuit or a primary circuit? That is the question.
I would say that its
a secondary circuit, but that's only my opinion, or interpretation.

>REH> The dielectric strength requirements have been increased by a
>factor of 1.6x.

Yes, according to Annex ZB (6.1.2.1), this 1.6x (2400Vac or 3394Vdc)
dielectric test applies only to
solid insulation of semiconductor components. Thinking about it, this new 1.6x
dielectric test
requirement may force some semiconductor bridging component sourcing changes
for manufacturers.

OK, its clear (well, sort of). Basic insulation is now required, but with
supplementary insulation
features (basimentary insulation, if you will :->), given Annex ZB (6.1.2.1)
of EN60950-1.

Comments?

Best regards,

Ron Pickard
rpick...@hypercom.com


  

  richhug...@aol.co   

  mTo:  
j...@randolph-telecom.com  
   
   cc:  
rpick...@hypercom.com, emc-p...@majordomo.ieee.org        
   
  01/08/2004 02:21 Subject:  RE: EN60950-1,TNV to
Earth Insulation 
  PM  

  

  



Ron,

Joe Randolph wrote:

 > Hi Ron:
 >
 > In my interpretation of EN 60950-1, the insulation requirement is the
 > one contained in the main body of the text, UNLESS it is modified in
 > Annex ZB.  In that case, the modifications called out in Annex ZB also
 > apply.

REH> Pretty much, except more precisely the requirements of Annex ZB
replace any conflicting requirements in the body of the standard in
Finland, Norway and Sweden (in this particular case).

 >
 > So, there has in fact been a relaxation of the traditional Nordic
 > requirement for supplementary insulation.  The revised Annex ZB retains
 > only the solid insulation aspects of supplementary insulation.  The
 > creepage, clearance, and electric strength requirements are now the ones
 > in the main body of the document, namely, basic insulation for a
 > secondary circuit.

REH> It is my belief that the dielectric withstand test is that required
for basic insulation for a PRIMARY circuit, not a SECONDARY circuit -
although I agree the requirement is not as clear as it could be.
REH> If you look at   Annex ZB it tells you to "add the following text
between the first and second paragraph", part of the text being "each of
which shall pass the electric strength test below" and the second para
has the text "insulation shall have a minimum d.c. sparkover voltage of
1,6 times the 

RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

In a messaged date 1/8/2004, Richard Hughes writes:

> It is my belief that the dielectric withstand test is that required 
> for basic insulation for a PRIMARY circuit, not a SECONDARY circuit - 
> although I agree the requirement is not as clear as it could be.
> If you look at   Annex ZB it tells you to "add the following text 
> between the first and second paragraph", part of the text being "each
of 
> which shall pass the electric strength test below" and the second para

> has the text "insulation shall have a minimum d.c. sparkover voltage
of 
> 1,6 times the RATED VOLTAGE or 1,6 times the upper voltage of the
RATED 
> VOLTAGE RANGE of the equipment"

> The dielectric strength requirements have been increased by a 
> factor of 1.6x.



Hi Richard:

It appears that we are in agreement on most points except the one
excerpted above.  I think the problem is that the wording in Annex ZB is
very poor and can be interpreted different ways.  

I interpret the Annex ZB reference to "the electric strength test below"
to be pointing to the values listed in the main body text of clause
6.1.2.1, namely, a test voltage of 1500 VRMS for installations where the
AC mains voltages exceeds 130 VRMS and a test voltage of 1000 VRMS
elsewhere.  I do not think that ordinary solid insulation has to be
tested to 1.6 times 1500 VRMS.

After laying out the requirement for ordinary solid insulation, Annex ZB
goes on to describe three special cases where alternate requirements can
be applied to the solid insulation:

1) A "semiconductor component" such as an opto isolator
2) A Y2 cap
3) A Y3 cap

The reference to a test of 1.6 times 1500 VRMS is for the first of these
special cases, "semiconductor components."

Just to make things more confusing, the main body text in clause 6.1.2.1
uses the same factor of 1.6 in a different context.  The statement that
surge suppressors must have a minimum sparkover of 1.6 times the RATED
VOLTAGE is referring to the nominal AC mains voltage, not the test
voltage for electric strength.  The RATED VOLTAGE is defined in clause
1.2.1.1 and would likely be about 250 VRMS for a product used in
Finland, Norway, or Sweden that is powered from the AC mains.

The other topic where we may not completely agree is the question of
whether the applicable requirement is for a primary circuit or a
secondary circuit.  I would argue that for the purposes of clause
6.1.2.1 this question is now moot, since there is no longer any
reference in clause 6.1.2.1 to a requirement where one first needs to
determine whether the circuit is a primary circuit or a secondary
circuit.

The place where this distinction still needs to be considered is the
basic insulation requirement in clause 2.3.2.  In this case the barrier
is between (SELV or TNV-1 or accessible parts) and (TNV-2 or TNV-3).  A
TNV circuit is considered to be a secondary circuit, so Table 2K applies
instead of Table 2H.

 
 
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com


> -Original Message-
> From: owner-emc-p...@majordomo.ieee.org 
> [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Richard Hughes
> Sent: Thursday, January 08, 2004 4:22 PM
> To: j...@randolph-telecom.com
> Cc: 'Ron Pickard'; emc-p...@majordomo.ieee.org
> Subject: RE: EN60950-1,TNV to Earth Insulation
> 
> 
> 
> Ron,
> 
> 
> 
> Joe Randolph wrote:
> 
>  > Hi Ron:
>  >
>  > In my interpretation of EN 60950-1, the insulation 
> requirement is the  > one contained in the main body of the 
> text, UNLESS it is modified in  > Annex ZB.  In that case, 
> the modifications called out in Annex ZB also  > apply.
> 
> REH> Pretty much, except more precisely the requirements of Annex ZB
> replace any conflicting requirements in the body of the standard in 
> Finland, Norway and Sweden (in this particular case).
> 
>  >
>  > So, there has in fact been a relaxation of the traditional 
> Nordic  > requirement for supplementary insulation.  The 
> revised Annex ZB retains  > only the solid insulation aspects 
> of supplementary insulation.  The  > creepage, clearance, and 
> electric strength requirements are now the ones  > in the 
> main body of the document, namely, basic insulation for a  > 
> secondary circuit.
> 
> REH> It is my belief that the dielectric withstand test is 
> that required
> for basic insulation for a PRIMARY circuit, not a SECONDARY circuit - 
> although I agree the requirement is not as clear as it could be.
> REH> If you look at   Annex ZB it tells you to "add the 
> following text 
> between the first and second paragraph", part of the text 
> being "each of 
> which sh

RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Ron,



Joe Randolph wrote:

 > Hi Ron:
 >
 > In my interpretation of EN 60950-1, the insulation requirement is the
 > one contained in the main body of the text, UNLESS it is modified in
 > Annex ZB.  In that case, the modifications called out in Annex ZB also
 > apply.

REH> Pretty much, except more precisely the requirements of Annex ZB 
replace any conflicting requirements in the body of the standard in 
Finland, Norway and Sweden (in this particular case).

 >
 > So, there has in fact been a relaxation of the traditional Nordic
 > requirement for supplementary insulation.  The revised Annex ZB retains
 > only the solid insulation aspects of supplementary insulation.  The
 > creepage, clearance, and electric strength requirements are now the ones
 > in the main body of the document, namely, basic insulation for a
 > secondary circuit.

REH> It is my belief that the dielectric withstand test is that required 
for basic insulation for a PRIMARY circuit, not a SECONDARY circuit - 
although I agree the requirement is not as clear as it could be.
REH> If you look at   Annex ZB it tells you to "add the following text 
between the first and second paragraph", part of the text being "each of 
which shall pass the electric strength test below" and the second para 
has the text "insulation shall have a minimum d.c. sparkover voltage of 
1,6 times the RATED VOLTAGE or 1,6 times the upper voltage of the RATED 
VOLTAGE RANGE of the equipment"
REH> That the requirement is for a PRIMARY circuit is also logical, 
given  the origional requirement for SUPLIMENTARY insulation for a 
PRIMARY circuit and an understanding of the Nordic concerns.


 >
 > Note that while this might lead you to conclude that the electric
 > strength requirement has been relaxed from the 1500 VRMS of
 > supplementary insulation, the 1500 VRMS requirement now appears in
 > clause 6.1.2.1 for cases where the AC mains voltage exceeds 130 VRMS.
 > This change (an increase from the previous requirement of 1000 VRMS)
 > took place when the 3rd edition of EN 60950 was issued in the year 2000.
 > That same edition was the first time the reference to supplementary
 > insulation disappeared from Annex ZB.
 >
 > You ask whether the solid insulation requirements in Annex ZB apply to
 > printed wiring boards.  In my interpretation they certainly do.  In
 > earlier versions of Annex ZB that explicitly called out supplementary
 > insulation, there was always the option of using the various printed
 > circuit board construction methods that now appear in clause 2.10.5.3 of
 > EN 60950-1 (these options have appeared in earlier editions in different
 > clauses).  Now that Annex ZB makes no explicit reference to
 > supplementary insulation, some people might argue that the options
 > described in clause 2.10.5.3 can not be used.  I think these options can
 > still be used, but doing so might require some additional justification
 > to show that the result complies with the "2 thin layers" option in
 > Annex ZB.
 >
REH> Yes, the solid insulation requirements would apply to most pcbs 
with the proviso's mentioned by Joe.

 > In summary, the net effect of the changes for Finland, Norway, and
 > Sweden is that the creepage and clearance requirements have been
 > relaxed, but the requirements for solid insulation and electric strength
 > remain the same as they were when the requirement called out
 > supplementary insulation.

REH> The dielectric strength requirements have been increased by a 
factor of 1.6x.

 >
 > By the way, I have formed the impression that the reason for the
 > difference between the IEC version and the EU version is that there have
 > been ongoing efforts to get the Nordic countries to drop their
 > insistence on supplementary insulation and harmonize their requirement
 > with the rest of the EU (and in fact, the rest of the countries
 > worldwide that base their requirements on IEC 60950).  I think the
 > difference that we see is the result of a compromise that was worked out
 > between the time that the IEC version was completed and the time that
 > the EU version was published.
 >
REH> True
 >
 >
 > Joe Randolph
 > Telecom Design Consultant
 > Randolph Telecom, Inc.
 > 781-721-2848 (USA)
 > j...@randolph-telecom.com
 > http://www.randolph-telecom.com
 >
 >
 > > -Original Message-----
 > > From: owner-emc-p...@majordomo.ieee.org
 > > [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Ron Pickard
 > > Sent: Wednesday, January 07, 2004 4:38 PM
 > > To: richhug...@aol.com
 > > Cc: emc-p...@majordomo.ieee.org
 > > Subject: Re: EN60950-1,TNV to Earth Insulation
 > >
 > >
 > >
 > >
 > > Hi Richard,
 > >
 > >

RE: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Hi Ron:

In my interpretation of EN 60950-1, the insulation requirement is the
one contained in the main body of the text, UNLESS it is modified in
Annex ZB.  In that case, the modifications called out in Annex ZB also
apply.

So, there has in fact been a relaxation of the traditional Nordic
requirement for supplementary insulation.  The revised Annex ZB retains
only the solid insulation aspects of supplementary insulation.  The
creepage, clearance, and electric strength requirements are now the ones
in the main body of the document, namely, basic insulation for a
secondary circuit.

Note that while this might lead you to conclude that the electric
strength requirement has been relaxed from the 1500 VRMS of
supplementary insulation, the 1500 VRMS requirement now appears in
clause 6.1.2.1 for cases where the AC mains voltage exceeds 130 VRMS.
This change (an increase from the previous requirement of 1000 VRMS)
took place when the 3rd edition of EN 60950 was issued in the year 2000.
That same edition was the first time the reference to supplementary
insulation disappeared from Annex ZB.

You ask whether the solid insulation requirements in Annex ZB apply to
printed wiring boards.  In my interpretation they certainly do.  In
earlier versions of Annex ZB that explicitly called out supplementary
insulation, there was always the option of using the various printed
circuit board construction methods that now appear in clause 2.10.5.3 of
EN 60950-1 (these options have appeared in earlier editions in different
clauses).  Now that Annex ZB makes no explicit reference to
supplementary insulation, some people might argue that the options
described in clause 2.10.5.3 can not be used.  I think these options can
still be used, but doing so might require some additional justification
to show that the result complies with the "2 thin layers" option in
Annex ZB.

In summary, the net effect of the changes for Finland, Norway, and
Sweden is that the creepage and clearance requirements have been
relaxed, but the requirements for solid insulation and electric strength
remain the same as they were when the requirement called out
supplementary insulation.

By the way, I have formed the impression that the reason for the
difference between the IEC version and the EU version is that there have
been ongoing efforts to get the Nordic countries to drop their
insistence on supplementary insulation and harmonize their requirement
with the rest of the EU (and in fact, the rest of the countries
worldwide that base their requirements on IEC 60950).  I think the
difference that we see is the result of a compromise that was worked out
between the time that the IEC version was completed and the time that
the EU version was published.

 
 
Joe Randolph
Telecom Design Consultant
Randolph Telecom, Inc.
781-721-2848 (USA)
j...@randolph-telecom.com
http://www.randolph-telecom.com


> -Original Message-
> From: owner-emc-p...@majordomo.ieee.org 
> [mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Ron Pickard
> Sent: Wednesday, January 07, 2004 4:38 PM
> To: richhug...@aol.com
> Cc: emc-p...@majordomo.ieee.org
> Subject: Re: EN60950-1,TNV to Earth Insulation
> 
> 
> 
> 
> Hi Richard,
> 
> Thanks for your detailed response. However, Annex ZB 
> (6.1.2.1) only pertains to insulation that is solid or forms 
> part of a semiconductor component, to Y2 capacitors and to Y3 
> capacitors with conditions. Is the reference to solid 
> insulation meant to include printed wiring boards? If not, 
> then basic insulation for a secondary circuit is all that's 
> required now. So, basically (please excuse the pun), the only 
> missing part of the TNV-SELV insulation equation would be the 
> working voltage across the barrier. Is this a fair assessment?
> 
> Best regards,
> 
> Ron Pickard
> rpick...@hypercom.com
> 
> 
>   
>   
>
>   richhug...@aol.co   
>   
>
>   mTo:   
> rpick...@hypercom.com 
> 
>cc:   
> emc-p...@majordomo.ieee.org   
> 
>   01/07/2004 01

Re: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Hi Richard,

Thanks for your detailed response. However, Annex ZB (6.1.2.1) only pertains
to insulation that is
solid or forms part of a semiconductor component, to Y2 capacitors and to Y3
capacitors with
conditions. Is the reference to solid insulation meant to include printed
wiring boards? If not,
then basic insulation for a secondary circuit is all that's required now. So,
basically (please
excuse the pun), the only missing part of the TNV-SELV insulation equation
would be the working
voltage across the barrier. Is this a fair assessment?

Best regards,

Ron Pickard
rpick...@hypercom.com


  

  richhug...@aol.co   

  mTo:   rpick...@hypercom.com

   cc:  
emc-p...@majordomo.ieee.org   
   
  01/07/2004 01:34 Subject:  Re: EN60950-1,TNV to
Earth Insulation 
  PM  

  

  




Ron,

When you look at "in some countries" notes in IEC standards you will see
that they have all disappeared when it comes to CENELEC standards
(unless the publishing organisation hasn't done its job correctly).
The reason for this is because European deviations are relocated to
Annex ZB or Annex ZC and all non-European deviations are just stripped
out all together.

Annex ZB contain what is known as "Special National Conditions".  As the
term implies, they are applicable in some countries only (i.e. not
across the whole of Europe - such things are called "Common
Modifications") and they result from characteristic (e.g. the local
environment) or practice (commonly building wiring regulations /
national electric codes) that cannot be changed even over a long
period.  Look here and this is where you will find the deviations for
Finland, Norway and Sweden that relate to clause 6.1.2.1.


Annex ZC contain what is known as "A-deviations".  Typically these stem
>from national laws.  You will see that there is a Note that states that
  "it is the view of the Commission of the European Communities ... that
compliance with A-deviations is no longer mandatory and that the free
movement of products complying with such a standard should not be
restricted except under the safeguard procedure provided for in the
relevant Directive". Of course, if a company chooses to ignore these
deviations and is prosecuted for failure to comply with some national
law or other, the opinion of the European Commission may be moot.

But what of Annex ZA?  That is just a list of standards that have been
Normatively referred to (they must be met, where they are specifically
called up) where the references to international publications have been
replaced by their relevant European counterparts.

Now to your specific question...

Is supplementary insulation for a primary circuit still required in
order to comply with clause 6.1.2.1?

Short Answer, NO.

Detailed Answer, See Annex ZB (Page 252 if you have BS EN 60950-1).

Best regards,

Richard Hughes

Safety Answers Ltd
www.safetyanswers.ltd.uk





Ron Pickard wrote:

 >
 > To all those knowledgeable with the 60950 series of safety standards,
 >
 > I've just been able to receive my copy of EN60950-1 (I've had IEC
 > 60950-1 for some time now). Upon
 > leafing thru EN60950-1, I noticed something missing that was in notes
 > 1 & 2 of clause 6.1.2.1 of
 > IEC60950 3rd Ed. That being, the requirement for supplementary
 > insulation for a primary circuit for
 > Norway and Sweden from TNV to earth. And looking into IEC60950-1, the
 > note in clause 6.1.2.1 states
 > "In Finland, Norway and Sweden, there are additional requirements for
 > the insulation."
 > Unfortunately, I've looked in clauses 2.3, 2.9, 2.10 and 6.1, but
 > cannot find these additional
 > requirements (even the CB Bulletin appears to provide only solid
 > insulation requirements for
 > 6.1.2.1). And to make this matter a bit more obtuse, both notes in
 > clause 6.1.2.1 has been deleted
 > from EN60950-1 according to Annex NA.
 >
 > So I h

Re: EN60950-1,TNV to Earth Insulation

[owner-emc-p...@majordomo.ieee.org]

Ron,

When you look at "in some countries" notes in IEC standards you will see 
that they have all disappeared when it comes to CENELEC standards 
(unless the publishing organisation hasn't done its job correctly). 
The reason for this is because European deviations are relocated to 
Annex ZB or Annex ZC and all non-European deviations are just stripped 
out all together.

Annex ZB contain what is known as "Special National Conditions".  As the 
term implies, they are applicable in some countries only (i.e. not 
across the whole of Europe - such things are called "Common 
Modifications") and they result from characteristic (e.g. the local 
environment) or practice (commonly building wiring regulations / 
national electric codes) that cannot be changed even over a long
period.  Look here and this is where you will find the deviations for 
Finland, Norway and Sweden that relate to clause 6.1.2.1.


Annex ZC contain what is known as "A-deviations".  Typically these stem 
>from national laws.  You will see that there is a Note that states that 
  "it is the view of the Commission of the European Communities ... that 
compliance with A-deviations is no longer mandatory and that the free 
movement of products complying with such a standard should not be 
restricted except under the safeguard procedure provided for in the 
relevant Directive". Of course, if a company chooses to ignore these 
deviations and is prosecuted for failure to comply with some national 
law or other, the opinion of the European Commission may be moot.

But what of Annex ZA?  That is just a list of standards that have been 
Normatively referred to (they must be met, where they are specifically 
called up) where the references to international publications have been 
replaced by their relevant European counterparts.

Now to your specific question...

Is supplementary insulation for a primary circuit still required in 
order to comply with clause 6.1.2.1?

Short Answer, NO.

Detailed Answer, See Annex ZB (Page 252 if you have BS EN 60950-1).

Best regards,

Richard Hughes

Safety Answers Ltd
www.safetyanswers.ltd.uk





Ron Pickard wrote:

 >
 > To all those knowledgeable with the 60950 series of safety standards,
 >
 > I've just been able to receive my copy of EN60950-1 (I've had IEC
 > 60950-1 for some time now). Upon
 > leafing thru EN60950-1, I noticed something missing that was in notes
 > 1 & 2 of clause 6.1.2.1 of
 > IEC60950 3rd Ed. That being, the requirement for supplementary
 > insulation for a primary circuit for
 > Norway and Sweden from TNV to earth. And looking into IEC60950-1, the
 > note in clause 6.1.2.1 states
 > "In Finland, Norway and Sweden, there are additional requirements for
 > the insulation."
 > Unfortunately, I've looked in clauses 2.3, 2.9, 2.10 and 6.1, but
 > cannot find these additional
 > requirements (even the CB Bulletin appears to provide only solid
 > insulation requirements for
 > 6.1.2.1). And to make this matter a bit more obtuse, both notes in
 > clause 6.1.2.1 has been deleted
 > from EN60950-1 according to Annex NA.
 >
 > So I have to ask, is supplementary insulation for a primary
 > circuit still required here? If so,
 > where is the requirement actually stated? Or, is supplementary
 > insulation for a secondary circuit,
 > or even basic insulation, now acceptable for Norway and Sweden?
 >
 > Or, have I overlooked something? I'm trying get thru the cobwebs back
 > to daylight and I'm hoping
 > that you will help me and maybe others with the same question(s).
 >
 > I look forward to your replies. Please advise.
 >
 > Best regards,
 >
 > Ron Pickard
 > rpick...@hypercom.com
 >
 >
 >
 >
 > ---
 > This message is from the IEEE EMC Society Product Safety
 > Technical Committee emc-pstc discussion list.
 >
 > Visit our web site at:  http://www.ieee-pses.org/
 >
 > To cancel your subscription, send mail to:
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 >  Jim Bacher: j.bac...@ieee.org
 >
 > All emc-pstc postings are archived and searchable on the web at:
 > http://www.ieeecommunities.org/emc-pstc
 >




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All emc-pst

RE: EN60950-1 - Time Scale??

[Kevin Richardson]

Peter,
 
For Australia & New Zealand 
AS/NZS 60950-1 has completed the public comment period.  There a couple of
comments which need to be resolved but hopefully these will not hold it up too
much.
As such, with any luck it should be published within a few months.
 

Best regards, 
Kevin Richardson 

Stanimore Pty Limited 
Compliance Advice & Solutions for Technology 
(Legislation/Regulations/Standards/Australian Agent Services) 
Ph:   02-4329-4070   (Int'l: +61-2-4329-4070) 
Fax:  02-4328-5639   (Int'l: +61-2-4328-5639) 
Mobile:  04-1224-1620   (Int'l: +61-4-1224-1620) 
Email:kevin.richard...@ieee.org 

This material (this message and the information contained in all attachments
to this message) is confidential and/or privileged information and is intended
only for the addressee/s named above. Any unauthorised dissemination, copying,
use of or reliance upon this material by persons or entities other than the
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please notify Stanimore Pty Limited and destroy all copies (electronic and
hardcopy) of this message and all attachments immediately.


From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of peter merguerian
Sent: Friday, 7 February 2003 5:09 AM
To: emc-p...@majordomo.ieee.org
Subject: EN60950-1 - Time Scale??



Group,

EN60950-1 appears in the OJ and there is a CB TRF issued by Fimko to this
standard. 

Is it wise to obtain a CB Test Report and Certificate to this standard when
most countries, including the US and Canada, have not adopted their versions
of the standard?

What is going on around the world to adopt the IEC 60950-1 standard?

 

Peter




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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[peter merguerian]

Dear Friends,

Thanks very much to the input regarding CB Tripping During Fault Testing.
There were many thoughts on the subject and I am sure that next time the wall
CB trips during fault tests at your third part certification laboratory, you
have something to talk about - make sure they do not charge you for the
discussion time!

Peter




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Yahoo! Mail Plus 
 - Powerful. Affordable. Sign up now http://mailplus.yahoo.com> 

RE: EN60950-1 - Time Scale??

[Richard Hughes]

Peter, 

 

To answer your question directly, I would say that it is the choice of the
manufacture, based on their market (international or just European) and
product lifetime to make their decisions.

 

For instance, the OJEC in relation to the LVD states that the third amendment
to EN 60950 has a date of cessation of 1/7/2006: therefore, if a manufacturer
is today placing a product on the European market that has a product life that
extends beyond 1/7/2006 then they may well consider it useful to adopt EN
60950-1 now.  However, if the manufacturer's product only has a market life of
a couple of years and they want to make maximum use of the IECEE CB Scheme to
gain multiple approvals across the world then they may decide that one of the
earlier variants of IEC 60950 would be a better way to go.

 

In fact, I would like to ask a completely different but related question. 
Given that Europe ratified EN 60950-1 in December 2001, why has it taken so
long for other countries to adopt IEC 60950-1 as their own national standard? 
Particularly so for those countries whose native language is English or French
and so the task of translation should be minimal.

 

While on the subject of what's going on around the world to adopt IEC 60950-1,
perhaps you have some information regarding the situation in Israel?

 

Regards,

 

Richard Hughes


From: peter merguerian [mailto:pmerguerian2...@yahoo.com]
Sent: 06 February 2003 18:09
To: emc-p...@majordomo.ieee.org
Subject: EN60950-1 - Time Scale??



Group,

EN60950-1 appears in the OJ and there is a CB TRF issued by Fimko to this
standard. 

Is it wise to obtain a CB Test Report and Certificate to this standard when
most countries, including the US and Canada, have not adopted their versions
of the standard?

What is going on around the world to adopt the IEC 60950-1 standard?

Peter




  _  

Do you Yahoo!?
Yahoo! Mail  
Plus - Powerful. Affordable. Sign up  <
ttp://rd.yahoo.com/mail/mailsig/*http://mailplus.yahoo.com> now

Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Rich Nute]

Hi Peter:


My comments were based on the proposed requirement to
test the PE path with the circuit prospective current
transient, e.g. 200 amps from a 10,000-amp source for 
the period of time required to operate the overcurrent 
device  -- say less than a second or so.

(The 200 amps is a function of the contact resistances 
and the wire resistances, independent of the fault; 
the duration is a function of the overcurrent device.
200 amps is a reasonable number for plug-and-socket
cord-connected products.)

In order to get this maximum current, the fault must
be near zero ohms for the duration of the current
transient.  

To achieve near-zero ohms, the fault must be a large-
area fault.  A small-area fault is likely to fuse
open due to the current density and resistance at the
contact.

(I had the unfortunate experience that such a test by
a cert house used a small-area contact at a point where
no basic insulation fault could occur; the PWB PE path
was destroyed.  We repeated the test at a large-area
contact where basic insulation could fault, and the
PWB PE path passed.)

>   What if the over current device operates, the earthing path
>   is compromised by the fault, but not destroyed?  

I believe this is the objective of the proposal -- to
test the PE path with the circuit prospective current.
I would expect the compliance criterion to be no damage 
to the PE path.

>   What if the fault is of nonnear-zero impedance, the earthing
>   path is damaged, but not opened, and resetting of the
>   breaker does occur, but at some point the breaker holds due
>   to the relatively high impedance?

This scenario moves from withstanding the circuit 
prospective current to withstanding the steady-state
current just below the operating point of the over-
current device.  

I suggest that this is the objective of the existing 
requirement to test at twice the overcurrent device
rating or 25 amps, whichever is less.

>   a relatively complex earthing path, I have prepared a
>   separate e-mail that includes some construction details and
>   empirical data for a product in my lab.  To be sent soon.

I appreciate you sharing this data.


Best regards,
Rich






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RE: EN60950 protective conductor test

[boconn...@t-yuden.com]

Sir 

Based on *anecdotal* experience, use of PWB trace for P.E. is common only in
SMPSs that have no chassis or surrounding frame. For example, my employer,
mostly for the reasons published in this thread, does not use a PWB-only P.E
on any (AC/DC converter) SMPS. While my employer offers some frame-less DC/DC
converters that do have a "de-facto" PW-based P.E., none are intended for the
TNV enviroment.

And, AFAIK, all Class 1 SMPS should have a chassis-based P.E. 

R/S, 
Brian 

-Original Message- 
From: John Woodgate 

I read in !emc-pstc that Rich Nute  wrote (in 
<200302051810.kaa05...@epgc264.sdd.hp.com>) about 'EN60950 protective 
conductor test' on Wed, 5 Feb 2003: 

>In my experience, PWB PE circuits are common, 
>and most difficult to obviate. 

So says our SMPS expert on the national committee. Well, chacun à son 
gout: I'll do my best to avoid them entirely. 
-- 
Regards, John Woodgate 

RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Peter L. Tarver]

This thread has been largely theoretical.  Let's look at
some empirical test results for a product I just completed
testing.

The product has a redundant power configuration and nearly
identical current paths for each of two power supplies,
though one has about 2 in. longer traces on one side of one
of the boards involved.  There is no supplementary
overcurrent protection between the appliance inlets and the
input connections of the power supplies.

The earthing path involves the following:

filtered appliance inlet -->
quick-disconnect on filter -->
~1.5 in. No. 18 AWG terminated in a ring lug -->
earthing stackup on a PEM stud of ring lug (from filter),
KEPS nut, ring lug for downstream earthing, KEPS nut -->
~15 in. No. 18 AWG to a header style, soldered through-hole
interconnect -->
traces -->
soldered through-hole interconnect (for hot swappable power
supply) -->
soldered through-hole interconnect -->
traces -->
soldered through-hole to a header style, interconnect -->
~9 in. No. 18 AWG -->
soldered through-hole to a header style, interconnect on the
power supply -->
internal power supply magic -->
large, open-frame heatsink on power supply

This testing was first performed in situ and as intended in
normal use.  I believe this test configuration should be
used for the purposes of safety certification.

In each of the following cases, the earthing impedance test
current was maintained for 2 minutes.  These tests were
performed "precompliance."

I first tested the shortest path.

before faulting test current: 20.0 A
after faulting test current: 20.4 A

before faulting: 0.008 Ohm (a 0.016 V drop across the path)
after faulting: 0.006 Ohm (a 0.012 V drop across the path)

Surprising to have a lower impedance final result.  So much
so, I assumed I must have done something incorrectly,
reflowed a bad solder joint, initiated metal migration ...
something, either during the fault test, the earthing
impedance test or both.

Based on the product's construction, I knew that some
incidental current paths contributed to the very low
earthing impedance.  I then removed the assemblies of
interest from the main chassis and retested on the other of
the two circuits, so that only the current path of specific
interest was involved.  I left the main protective earthing
connection intact on the chassis.  Testing the longest path,

before faulting test current: 20.5 A
after faulting test current: 20.4 A

before faulting: 0.038 Ohm (a 0.77 V drop across the path)
after faulting: 0.037 Ohm (a 0.75 V drop across the path)

Still compliant at a ~20 A current value and still an
apparent *reduction* in the impedance of the earthing path.
This is not coincidence and double checking my test methods
along the way told me there were no errors.

I performed a third test on the same sample, longest path,
still outside the enclosure.

before faulting test current: 20.4 A
after faulting test current: 30.2 A

before faulting: 0.036 Ohm (a 0.74 V drop across the path)
after faulting: 0.041 Ohm (a 1.24 V drop across the path)


The above testing was repeated in situ on a new test sample.
The earthing impedance test, before and after, was set to 40
A.  The results were very similar to those for the first in
situ test, with almost identical calculated impedances, and
the earthing path withstood the 40 A current very nicely.

It should be noted that I performed the fault on a 120V, 20
A branch circuit.  The product will be rated for 240 V and
CSA 22.2 No. 0.4 requires the test be performed on a circuit
with the voltage at the highest rating marked on the
product, but I only have 20 A circuits on 120V circuits; my
208 V circuits, which I can boost to 240V, are all 30 A.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com





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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Peter L. Tarver]

> From: Rich Nute
> Sent: Wednesday, February 05, 2003 12:20 PM
>
> Hi Peter:

Hi, Rich.

> This test implies a near 0-ohm fault to the
> PE, where the PE circuit includes a PE trace
> on the PWB.

That's a reasonable assumption and is convenient for the
purposes of testing.  It is unlikely to be the only fault
case, but that's irrelevant to compliance with the standard
and should be considered internally, to the level of pain
tolerable by any particular company.

> If there is a zero-ohm fault, an over-current
> device, somewhere, will operate.  (Indeed, this
> is the function of the PE circuit!)  A zero-ohm
> fault implies a large-area contact with a fair
> amount of contact pressure for at least the
> period of time to operate the overcurrent device.
>
> Consequently, the product must be removed from
> service and repaired before being returned to
> service.

What if the over current device operates, the earthing path
is compromised by the fault, but not destroyed?  Let us not
forget that there are many who will reset a circuit breaker
ad infinitum, to failure, reimposing a fault repeatedly.  (I
spoke this afternoon to a coworker who is also landlord.
One tenant consistently overloaded a branch circuit and
reset the circuit breaker repeatedly, until it failed to
close.)

Each resetting of the circuit imposes a similar fault, with
a progressively weaker earthing circuit.  Let us assume that
at some point short of circuit breaker failure, the earthing
path becomes compromised enough that the branch circuit does
not open the circuit.

What if the fault is of nonnear-zero impedance, the earthing
path is damaged, but not opened, and resetting of the
breaker does occur, but at some point the breaker holds due
to the relatively high impedance?

We can let our imaginations wander from there and each
believe as we will that thus and such will or will not,
could or could not happen and debate the probabilities until
the ruminants return hither.  Bad stuff happens: dead-front
switchboards explode, fires are started by minor appliances
with safety certification house marks or questionable wiring
practices, trains jump the tracks...


> If the 0-ohm fault is on the PWB, then the PWB
> will need to be replaced.  It is difficult to
> imagine a fault of 0-ohm proportions that could
> be repaired without replacing the PWB assembly.
> Indeed, if the PWB PE circuit carries the high
> transient current, it may very well be that the
> supply conductors on the PWB may be blown off
> the PWB.  So, I question whether the compliance
> criteria need be applied.

If.  The fault might occur anywhere in the earthing path.
To give an idea of how a relatively simple idea can lead to
a relatively complex earthing path, I have prepared a
separate e-mail that includes some construction details and
empirical data for a product in my lab.  To be sent soon.


> >   There is also the much more variable solder
> in the earthing
> >   path.  While manufacturing techniques have
> come a long way
> >   in terms of consistency, the amount of solder
> in a joint and
> >   the quality of the joint itself can play a
> significant role.
> >   It should be expected that a lower melting
> point solder will
> >   perform less well than a higher melting point solder.
> >   Appropriate process controls will have a
> positive effect.
>
> An ideal solder joint involves an amalgam at
> the joint with the conductors.  The properties
> of the amalgam are typically "greater" than
> the property of either material alone.  As in
> copper plumbing joints, an idea joint has very
> little solder between the two components being
> joined.

And yet, mass production of electrical and electronic
products, while generally yielding consistent-quality
products when produced in a conscientious environment, can
still have variability and initially undetectable problems
that even HALT testing can't predict and HASS testing can't
weed out.  There will be very few companies with zero field
returns where cracks develop in a laminate, solder joints
fail or are imperfect to the point of eventually some flaw
eventually rears its head.

The goal is to at least offer the impression that a
construction will not yield an insidious hazard at some
point in the future.  My recent experience has led me to
believe that, aside from a few head scratching results, the
test is *very* simple to perform and requires almost *no*
additional test equipment, over and above an earthing
impedance test setup and a modicum of ingenuity inherent in
any engineer.

> My guess would be that the current path will be
> that of least resistance, which will minimize
> the current through the solder around the joint.
> So, I would doubt that the solder (of a good
> joint) would be much affected by the current
> pulse.
>
>
> Best regards,
> Rich

There's no question that incidental currents can have a
positive effect, even if not considered "reliable."  There's
no denying that it is possible to comply with the 

Re: EN60950 protective conductor test

[John Woodgate]

I read in !emc-pstc that Rich Nute  wrote (in
<200302051810.kaa05...@epgc264.sdd.hp.com>) about 'EN60950 protective
conductor test' on Wed, 5 Feb 2003:

>In my experience, PWB PE circuits are common, 
>and most difficult to obviate.

So says our SMPS expert on the national committee. Well, chacun à son
gout: I'll do my best to avoid them entirely. 
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Rich Nute]

Hi Peter:


>   Not quite.  I^2·t will tell you the let through current of
>   the copper trace, but will not necessarily tell you if the
>   construction will be compliant.  The compliance criteria for
>   this test include:
>   
>   * no damage to the trace (no lifting, probably no
>   discoloration)
>   * no damage to the PWB (no delamination, burning; I don't
>   know if this includes burning off of solder mask)
>   * before and after earthing impedance must comply with the
>   0.1 Ohm maximum impedance
>   * no change in earthing impedance greater than 10% of the
>   before and after earthing impedance results

This test implies a near 0-ohm fault to the
PE, where the PE circuit includes a PE trace 
on the PWB.

If there is a zero-ohm fault, an over-current
device, somewhere, will operate.  (Indeed, this
is the function of the PE circuit!)  A zero-ohm
fault implies a large-area contact with a fair
amount of contact pressure for at least the 
period of time to operate the overcurrent device.

(A point-contact fault would blow a hole in the
copper trace due to very high current density
at the point of contact.)

Consequently, the product must be removed from
service and repaired before being returned to
service.

If the 0-ohm fault is on the PWB, then the PWB
will need to be replaced.  It is difficult to
imagine a fault of 0-ohm proportions that could
be repaired without replacing the PWB assembly.
Indeed, if the PWB PE circuit carries the high
transient current, it may very well be that the
supply conductors on the PWB may be blown off
the PWB.  So, I question whether the compliance 
criteria need be applied.

>   There is also the much more variable solder in the earthing
>   path.  While manufacturing techniques have come a long way
>   in terms of consistency, the amount of solder in a joint and
>   the quality of the joint itself can play a significant role.
>   It should be expected that a lower melting point solder will
>   perform less well than a higher melting point solder.
>   Appropriate process controls will have a positive effect.

An ideal solder joint involves an amalgam at 
the joint with the conductors.  The properties
of the amalgam are typically "greater" than 
the property of either material alone.  As in
copper plumbing joints, an idea joint has very
little solder between the two components being
joined.

My guess would be that the current path will be
that of least resistance, which will minimize
the current through the solder around the joint.
So, I would doubt that the solder (of a good
joint) would be much affected by the current
pulse.


Best regards,
Rich





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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Rich Nute]

Hi Chris:


>   It seems funny to me that most equipment has been historically made with
18AWG protective ground pigtail wires; and 25A ground fault tests have been
used for years.  
>   
>   Now that PC  traces are being used for protective ground; we want to test
with 200A or greater impulse currents?  I'm curious about what would happen to
your typical 18AWG line cord during this test.  I'm wondering if the line cord
would fuse open? 

The 18 AWG readily passes the circuit prospective
current test.  This is because the current is
transient, and is cut off before the wire in the 
cord can reach fusing temperature.

>   One is at www.kepcopower.com/nomovax2.htm this is a nomograph of maximum
operating current, AWG and IR drop in the conductor.  The point "A" is
generally considered the point of maximum IR drop.  If you draw a line from
point "A", through a wire gauge size; you'll get a max current.  Of course
this is steady state current; and the nomograph assumes a single wire.  Wire
bundles would be a worse case.  It's too bad that this chart doesn't contain
the "fuse" values for the wires as well (the  I squared * T values).

Fusing currents for wires are published in:

Reference Data for Radio Engineers
International Telephone and Telegraph Corporation
67 Broad Street
New York 4, New York

This reference says "Courtesy of Automatic 
Electric Company, Chicago, Illinois."

The approximate fusing current for 18 AWG copper 
is 82.9 amperes.

The approximate fusing current of wires can be 
calculated from:

I  =  (K) * (d**3/2)

where d is the diameter of the wire, in inches
  K is a constant that depends on the metal

Here are some values for K:

copper:10,244
aluminum:   7,585
silver: 5,230
iron:   3,148
tin:1,642

The "Standard Handbook for Electrical Engineers"
by Fink and Beatty has some additional data,
including curves of current and time for each
AWG.  A couple of points for 18 AWG:

   0.1 second:~720 amps
   1.0 second:~220 amps
  10.0 second:~ 82 amps
   
>   3.  The third problem is mechanical.  Once Earth ground brought to a pad
on the circuitboard; then there is still the issue of getting a good
mechanical mate to the chassis with a wide surface area.  If the connection is
made through a couple of teeth on a star washer; then there is a potential for
localized heating.   I'm just going to maximize surface contact area for this
one.  I'm also considering using multiple board to chassis connection
locations.  Every screw that connects the board to chassis is a potential
Earth ground connection.

The problem with mechanical connections to PWBs 
by means of screws is that the PWB base material 
is a plastic and is subject to cold-flow under 
compressive conditions.  In the long-term, the
connection can loosen.  

Not everyone pays attention to this, and, in 
practice, it is rarely a problem.

One way around this is to use a wire from the 
board to the chassis.


Best regards,
Rich






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Re: EN60950 protective conductor test

[Rich Nute]

Hi John:


>   Is it not permitted to express a personal preference on this group? I
>   *prefer, personally*, not to use printed board traces as parts of the
>   PEC. I'm not suggesting that should be in IEC 60950 or any other
>   standard.

Of course we express personal preferences in
this group!  Almost every message is a personal
preference.  :-)

The point of my message is to argue against your
personal preference as there is nothing inherently
wrong with PWB traces as part of the PE circuit.

Some SMPS use a grounded heat sink -- on the PWB 
-- for the switching transistors.  In this case, 
the electrical circuit path from the heat sink to
the earth terminal of the IEC 60320 connector is
a part of the PE circuit, and must be capable of
carrying the fault current.  Running a wire from 
the heat sink to the terminal is a manual job, 
and introduces two connections that are operator-
dependent whereas the PWB connections are not.

Another point... which I hesitate to mention...
is that, while Y2 capacitors require connection 
to a PE return, some test houses require a PE 
return for Y1 capacitors!

In my experience, PWB PE circuits are common, 
and most difficult to obviate.


Best regards,
Rich






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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tr ipping Dring Fault Tests)

[drcuthbert]

I recently designed a piece of in-house gear that uses the PCB as part of
the protective earth GND return. At first I thought I would be forced to use
a wire(s) only (which was awkward given the mechanics of the unit) but then
was convinced that EN61010 did not require it. To get around the via issue
we kept the path on one PCB layer. We designed for well over 20 amps
continuous. The bare metal rear panel is connected to the power connector
GND with the standard YELLOW/GREEN wire. The cabinet and front panel are
connected through the PCB with either metal spacers or a metal bracket. When
testing this do I return the current through the rear panel only, or do two
more tests using the cabinet and the front panel? The cabinet and the front
panel do not have dedicated GND connections or any unpainted metal.

   Dave Cuthbert
   Micron Technology



From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Tuesday, February 04, 2003 11:25 AM
To: Lou Aiken; Peter L. Tarver; emc-p...@majordomo.ieee.org
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



PC traces are easier to assemble and the assembly can be done in a tighter
space.  I think (just an opinion)  that proper design could make this type
of system more reliable as well with less chances of wires coming loose...

> -Original Message-
> From: Lou Aiken [SMTP:ai...@gulftel.com]
> Sent: Tuesday, February 04, 2003 11:36 AM
> To:   Peter L. Tarver; emc-p...@majordomo.ieee.org
> Subject:  Re: EN60950 protective conductor test (was Re: Circuit
Breaker Tripping Dring Fault Tests)
> 
> 
> Why not provide a fuse to prevent deterioration of the PE trace on a PCB?
> 
> Joking of course, but now that I have your attention, I would like to see
> this thread move away from the physics and discuss what practical reasons
> there are for using PC traces to provide earth fault circuits.
> 
> 
> Lou Aiken, LaMer LLC
> 27109 Palmetto Drive
> Orange Beach, AL
> 36561 USA
> 
> tel ++ 1 251 981 6786
> fax ++ 1 251 981 3054
> Cell ++ 1 251 979 4648
> - Original Message -
> From: Peter L. Tarver 
> To: 
> Sent: Tuesday, February 04, 2003 9:53 AM
> Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
> Tripping Dring Fault Tests)
> 
> 
> 
> Not quite.  I^2·t will tell you the let through current of
> the copper trace, but will not necessarily tell you if the
> construction will be compliant.  The compliance criteria for
> this test include:
> 
> * no damage to the trace (no lifting, probably no
> discoloration)
> * no damage to the PWB (no delamination, burning; I don't
> know if this includes burning off of solder mask)
> * before and after earthing impedance must comply with the
> 0.1 Ohm maximum impedance
> * no change in earthing impedance greater than 10% of the
> before and after earthing impedance results
> 
> There is also the much more variable solder in the earthing
> path.  While manufacturing techniques have come a long way
> in terms of consistency, the amount of solder in a joint and
> the quality of the joint itself can play a significant role.
> It should be expected that a lower melting point solder will
> perform less well than a higher melting point solder.
> Appropriate process controls will have a positive effect.
> 
> These are some of the reasons some form of safety agency
> factory auditing of this type of construction is normal.
> 
> 
> Regards,
> 
> Peter L. Tarver, PE
> Product Safety Manager
> Sanmina-SCI Homologation Services
> San Jose, CA
> peter.tar...@sanmina-sci.com
> 
> 
> > -Original Message-
> > From: Chris Maxwell
> > Sent: Tuesday, February 04, 2003 5:32 AM
> >
> >
> > Exactly!
> >
> > Chris Maxwell
> >
> >
> > > -Original Message-
> > > From: drcuthbert [SMTP:drcuthb...@micron.com]
> > > Sent: Monday, February 03, 2003 7:50 PM
> > >
> > > What is needed is the I squared t rating of the
> > breaker. Then the (I^2)(t)
> > > rating of the PCB. Then you know if the PCB can
> > take it.
> > >
> > >Dave Cuthbert
> 
> 
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
> 
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
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> 
> For policy ques

RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Gary McInturff]

Lou,
I'm not proposing anything mind you, but you could save some space if 
you had
a PWB mounted appliance inlet and you would still have to get the PEC to the
chassis. 
Gary


From: Lou Aiken [mailto:ai...@gulftel.com]
Sent: Tuesday, February 04, 2003 8:36 AM
To: Peter L. Tarver; emc-p...@majordomo.ieee.org
Subject: Re: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



Why not provide a fuse to prevent deterioration of the PE trace on a PCB?

Joking of course, but now that I have your attention, I would like to see
this thread move away from the physics and discuss what practical reasons
there are for using PC traces to provide earth fault circuits.


Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

tel ++ 1 251 981 6786
fax ++ 1 251 981 3054
Cell ++ 1 251 979 4648

From: Peter L. Tarver 
To: 
Sent: Tuesday, February 04, 2003 9:53 AM
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



Not quite.  I^2·t will tell you the let through current of
the copper trace, but will not necessarily tell you if the
construction will be compliant.  The compliance criteria for
this test include:

* no damage to the trace (no lifting, probably no
discoloration)
* no damage to the PWB (no delamination, burning; I don't
know if this includes burning off of solder mask)
* before and after earthing impedance must comply with the
0.1 Ohm maximum impedance
* no change in earthing impedance greater than 10% of the
before and after earthing impedance results

There is also the much more variable solder in the earthing
path.  While manufacturing techniques have come a long way
in terms of consistency, the amount of solder in a joint and
the quality of the joint itself can play a significant role.
It should be expected that a lower melting point solder will
perform less well than a higher melting point solder.
Appropriate process controls will have a positive effect.

These are some of the reasons some form of safety agency
factory auditing of this type of construction is normal.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com


> -Original Message-
> From: Chris Maxwell
> Sent: Tuesday, February 04, 2003 5:32 AM
>
>
> Exactly!
>
> Chris Maxwell
>
>
> > -Original Message-
> > From: drcuthbert [SMTP:drcuthb...@micron.com]
> > Sent: Monday, February 03, 2003 7:50 PM
> >
> > What is needed is the I squared t rating of the
> breaker. Then the (I^2)(t)
> > rating of the PCB. Then you know if the PCB can
> take it.
> >
> >Dave Cuthbert



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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Chris Maxwell]

PC traces are easier to assemble and the assembly can be done in a tighter
space.  I think (just an opinion)  that proper design could make this type of
system more reliable as well with less chances of wires coming loose...

> -Original Message-
> From: Lou Aiken [SMTP:ai...@gulftel.com]
> Sent: Tuesday, February 04, 2003 11:36 AM
> To:   Peter L. Tarver; emc-p...@majordomo.ieee.org
> Subject:  Re: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)
> 
> 
> Why not provide a fuse to prevent deterioration of the PE trace on a PCB?
> 
> Joking of course, but now that I have your attention, I would like to see
> this thread move away from the physics and discuss what practical reasons
> there are for using PC traces to provide earth fault circuits.
> 
> 
> Lou Aiken, LaMer LLC
> 27109 Palmetto Drive
> Orange Beach, AL
> 36561 USA
> 
> tel ++ 1 251 981 6786
> fax ++ 1 251 981 3054
> Cell ++ 1 251 979 4648
> - Original Message -
> From: Peter L. Tarver 
> To: 
> Sent: Tuesday, February 04, 2003 9:53 AM
> Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
> Tripping Dring Fault Tests)
> 
> 
> 
> Not quite.  I^2·t will tell you the let through current of
> the copper trace, but will not necessarily tell you if the
> construction will be compliant.  The compliance criteria for
> this test include:
> 
> * no damage to the trace (no lifting, probably no
> discoloration)
> * no damage to the PWB (no delamination, burning; I don't
> know if this includes burning off of solder mask)
> * before and after earthing impedance must comply with the
> 0.1 Ohm maximum impedance
> * no change in earthing impedance greater than 10% of the
> before and after earthing impedance results
> 
> There is also the much more variable solder in the earthing
> path.  While manufacturing techniques have come a long way
> in terms of consistency, the amount of solder in a joint and
> the quality of the joint itself can play a significant role.
> It should be expected that a lower melting point solder will
> perform less well than a higher melting point solder.
> Appropriate process controls will have a positive effect.
> 
> These are some of the reasons some form of safety agency
> factory auditing of this type of construction is normal.
> 
> 
> Regards,
> 
> Peter L. Tarver, PE
> Product Safety Manager
> Sanmina-SCI Homologation Services
> San Jose, CA
> peter.tar...@sanmina-sci.com
> 
> 
> > -Original Message-
> > From: Chris Maxwell
> > Sent: Tuesday, February 04, 2003 5:32 AM
> >
> >
> > Exactly!
> >
> > Chris Maxwell
> >
> >
> > > -Original Message-
> > > From: drcuthbert [SMTP:drcuthb...@micron.com]
> > > Sent: Monday, February 03, 2003 7:50 PM
> > >
> > > What is needed is the I squared t rating of the
> > breaker. Then the (I^2)(t)
> > > rating of the PCB. Then you know if the PCB can
> > take it.
> > >
> > >Dave Cuthbert
> 
> 
> ---
> This message is from the IEEE EMC Society Product Safety
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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[John Barnes]

Chris,
Douglas Brooks wrote an article about Preese's and Onderdonk's equations
for fusing currents of wires, which was published in Printed Circuit
Magazine.  It can be downloaded from UltraCAD's web site at
http://www.ultracad.com/fusing.pdf

Appendix F of the book that I am writing for Kluwer, Robust Electronic
Design Reference, will cover the ampacity (current-carrying capacity) of
wires, printed circuit board traces, busbars, etc.  The manuscript is
due August 1st, so I had better get back to my writing...

John Barnes KS4GL, PE, NCE, ESDC Eng, SM IEEE
dBi Corporation
http://www.dbicorporation.com/


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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fa

[Cortland Richmond]

Lou Aiken wrote 

>> ... what practical reasons there are for using PC traces to provide
earth fault circuits. <<

One practical reason is, to cut costs and simplify construction. Some years
ago a former employer designed and made a computer power supply with the
safety ground on the board, and UL allowed it. It was necessary to make the
board rugged enough at the grounding point to accept a standard, threaded
stud, nut and washer combination; they would not budge on THAT. It survived
fault current tests just fine. 

What we got from this was the ability to put everything, including an IEC
power connector, on one board, and eliminate flying wires.

I've also seen current requirements which could not be reasonably met using
a PWB trace, and in that case, a heavy bus strap was soldered onto the
board. This is a viable replacement where space or fabrication constraints
don't allow for the heavy, wide traces high current incurs. This
construction may be a reasonable answer to  some of the issues here.

Cortland


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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[John Woodgate]

I read in !emc-pstc that Chris Maxwell  wrote
(in <83d652574e7af740873674f9fc12dbaaf7e...@utexh1w2.gnnettest.com>)
about 'EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)' on Tue, 4 Feb 2003:

>This would make heat dissipation different; and I would assume that it would 
>make the fusing characteristics (I^2)(t) slightly different as well.

Or even a lot different. The reason why I personally would not use a
printed board trace as a PEC is that boards can develop cracks and thin
copper patches, so I couldn't guarantee that every board would stand the
test that the test sample passed. In this case, I don't think
potentially destructive sample testing is adequate, either. The PEC
needs to be 'four nines' reliable.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Lou Aiken]

Why not provide a fuse to prevent deterioration of the PE trace on a PCB?

Joking of course, but now that I have your attention, I would like to see
this thread move away from the physics and discuss what practical reasons
there are for using PC traces to provide earth fault circuits.


Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

tel ++ 1 251 981 6786
fax ++ 1 251 981 3054
Cell ++ 1 251 979 4648

From: Peter L. Tarver 
To: 
Sent: Tuesday, February 04, 2003 9:53 AM
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



Not quite.  I^2·t will tell you the let through current of
the copper trace, but will not necessarily tell you if the
construction will be compliant.  The compliance criteria for
this test include:

* no damage to the trace (no lifting, probably no
discoloration)
* no damage to the PWB (no delamination, burning; I don't
know if this includes burning off of solder mask)
* before and after earthing impedance must comply with the
0.1 Ohm maximum impedance
* no change in earthing impedance greater than 10% of the
before and after earthing impedance results

There is also the much more variable solder in the earthing
path.  While manufacturing techniques have come a long way
in terms of consistency, the amount of solder in a joint and
the quality of the joint itself can play a significant role.
It should be expected that a lower melting point solder will
perform less well than a higher melting point solder.
Appropriate process controls will have a positive effect.

These are some of the reasons some form of safety agency
factory auditing of this type of construction is normal.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com


> -Original Message-
> From: Chris Maxwell
> Sent: Tuesday, February 04, 2003 5:32 AM
>
>
> Exactly!
>
> Chris Maxwell
>
>
> > -Original Message-
> > From: drcuthbert [SMTP:drcuthb...@micron.com]
> > Sent: Monday, February 03, 2003 7:50 PM
> >
> > What is needed is the I squared t rating of the
> breaker. Then the (I^2)(t)
> > rating of the PCB. Then you know if the PCB can
> take it.
> >
> >Dave Cuthbert



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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Peter L. Tarver]

Not quite.  I^2·t will tell you the let through current of
the copper trace, but will not necessarily tell you if the
construction will be compliant.  The compliance criteria for
this test include:

* no damage to the trace (no lifting, probably no
discoloration)
* no damage to the PWB (no delamination, burning; I don't
know if this includes burning off of solder mask)
* before and after earthing impedance must comply with the
0.1 Ohm maximum impedance
* no change in earthing impedance greater than 10% of the
before and after earthing impedance results

There is also the much more variable solder in the earthing
path.  While manufacturing techniques have come a long way
in terms of consistency, the amount of solder in a joint and
the quality of the joint itself can play a significant role.
It should be expected that a lower melting point solder will
perform less well than a higher melting point solder.
Appropriate process controls will have a positive effect.

These are some of the reasons some form of safety agency
factory auditing of this type of construction is normal.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com


> -Original Message-
> From: Chris Maxwell
> Sent: Tuesday, February 04, 2003 5:32 AM
>
>
> Exactly!
>
> Chris Maxwell
>
>
> > -Original Message-
> > From:   drcuthbert [SMTP:drcuthb...@micron.com]
> > Sent:   Monday, February 03, 2003 7:50 PM
> >
> > What is needed is the I squared t rating of the
> breaker. Then the (I^2)(t)
> > rating of the PCB. Then you know if the PCB can
> take it.
> >
> >Dave Cuthbert



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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tr ipping Dring Fault Tests)

[drcuthbert]

Chris,
I have estimated this type of thing in the past assuming adiabatic
conditions. That is, the energy put into the material heats it and no energy
is lost during the heating. This gives the worse-case temperature rise. So,
what is needed is the electrical resistance of the material and the specific
heat of the material. Let's look at the case of a trace sized to handle 25
amps continuously with a 40 degree C rise.
http://www.geocities.com/CapeCanaveral/Lab/9643/TraceWidth.htm

We will pulse it with 200 amps for 20 ms and see what the heat rise is
assuming adiabatic conditions:

The trace is 500 mils (1.27 cm) wide, 1 inch (2.54 cm) long, and is 1 oz
copper (1.4 mils or 3.55 x10^-3 cm). The resistance is 1 milliohm. The
energy absorbed is (I^2)(R)(t) = 0.8 joules. The density of copper is 8.96
gr/cm^3. The mass of this trace is 0.103 gr. The specific heat of copper is
0.386 J/gr*C. The specific heat of this trace is therefore 0.0398J/C which
gives a heat rise of 20 degrees C for a 200 amp, 20ms pulse.  I have
neglected the change in resistance and specific heat with temp.

I have actually viewed the voltage drop across a metal line as it was heated
by a pulse. From this one can plot the temperature versus time. The real
issue, I think are the vias and vias with heat reliefs. How many do we use?
We can calculate the vias the same way and come up with a recommendation. Of
course, it would be great to check this with experiments. I would be
interested in doing this if someone here wants to partner on the project. I
can have a test board designed and built and do the pulsing. What I need are
standards, suggestions, circuit breaker data, and any other help (such as
researching to see if we are reinventing the wheel. The results would then
be published in Compliance, Conformity, or Printed Circuit design magazine.


 Dave Cuthbert
 Micron Technology


From: Chris Maxwell [mailto:chris.maxw...@nettest.com]
Sent: Tuesday, February 04, 2003 6:32 AM
To: drcuthbert; John Woodgate; emc-p...@majordomo.ieee.org
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)


Exactly!  There is lots of data and tables available on the web for steady
state current; but I haven't found any sources that would give the (I^2)(t)
values for wires or PCB traces.   Such tables would take a great deal of
mystery out of this subject.  Right now, the best guess is to go by steady
state current rating; but there must be faults in this.  A PCB trace that
can handle 10 Amps of steady state current has a totally different geometry
than a wire that can handle 10 Amps of steady state current.  This would
make heat dissipation different; and I would assume that it would make the
fusing characteristics (I^2)(t) slightly different as well.

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 




> -Original Message-
> From: drcuthbert [SMTP:drcuthb...@micron.com]
> Sent: Monday, February 03, 2003 7:50 PM
> To:   'John Woodgate'; emc-p...@majordomo.ieee.org
> Subject:  RE: EN60950 protective conductor test (was Re: Circuit
Breaker Tripping Dring Fault Tests)
> 
> 
> What is needed is the I squared t rating of the breaker. Then the (I^2)(t)
> rating of the PCB. Then you know if the PCB can take it. 
> 
>Dave Cuthbert
> 
> 


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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Chris Maxwell]

Exactly!  There is lots of data and tables available on the web for steady
state current; but I haven't found any sources that would give the (I^2)(t)
values for wires or PCB traces.   Such tables would take a great deal of
mystery out of this subject.  Right now, the best guess is to go by steady
state current rating; but there must be faults in this.  A PCB trace that can
handle 10 Amps of steady state current has a totally different geometry than a
wire that can handle 10 Amps of steady state current.  This would make heat
dissipation different; and I would assume that it would make the fusing
characteristics (I^2)(t) slightly different as well.

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 




> -Original Message-
> From: drcuthbert [SMTP:drcuthb...@micron.com]
> Sent: Monday, February 03, 2003 7:50 PM
> To:   'John Woodgate'; emc-p...@majordomo.ieee.org
> Subject:  RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)
> 
> 
> What is needed is the I squared t rating of the breaker. Then the (I^2)(t)
> rating of the PCB. Then you know if the PCB can take it. 
> 
>Dave Cuthbert
> 
> 


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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tr ipping Dring Fault Tests)

[drcuthbert]

What is needed is the I squared t rating of the breaker. Then the (I^2)(t)
rating of the PCB. Then you know if the PCB can take it. 

   Dave Cuthbert


From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Monday, February 03, 2003 4:15 PM
To: emc-p...@majordomo.ieee.org
Subject: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)



I read in !emc-pstc that cnew...@xycom.com wrote (in <85256CC2.005F2DA4.
0...@notes.fw.xycom.com>) about 'EN60950 protective conductor test (was
Re: Circuit Breaker  Tripping Dring Fault Tests)' on Mon, 3 Feb
2003:

>My UL guy tells me that I should expect the typical service type CB to be
rated
>up to  + 10%.  So it appears that  I need to concern myself with a burst of
>current
>up to approximately 22 amps for the 20 amp AC circuit that my product is
being
>evaluated for.

Until it trips, your CB lets through the **whole 200 A**. The trip
current is practically irrelevant in this test; what matters is the trip
TIME. The board trace may stand 200 A for 50 ms but not for 100 ms.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk

Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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This message is from the IEEE EMC Society Product Safety
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RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Peter L. Tarver]

I've had extensive discussion with UL regarding the
performance of this test.  Below are my comments, taken from
these discussions.

> -Original Message-
> From: Carl Newton
> Sent: Monday, February 03, 2003 9:20 AM
>
>
> 1.  Three samples are tested;

Intended to demonstrate repeatability of the test results.

> 2.  Trace resistance is measured before and after
> test.  Resistance cannot
>   exceed 0.1 ohms, and cannot change more
> than 10% after test;

The test datasheets I have from UL state the impedance
before and after applying the fault is measured using an
ohmmeter.  I intend to use a lower current version of the
earthing impedance test for this purpose (say, 20A, rather
than 40A).

> 3.  AC source is 240 Vac, 200 amps (20A circuit
> breaker X 10), power factor
>   is 75 - 80% through shorted bus bars with a
> 20/30 A (20 in my case)
> service
>   entrance type circuit breaker in series
> with the testing terminals.  The
> circuit
>   breaker is connected to the bus bars by
> 1.22 m (4 ft.) of #12 AWG wire.

Some of this information is for the UL lab technician, in
order to increase the reproducibility of the results and
protect their equipment.  For instance:

*no power factor is specified in CSA 22.2 No. 0.4
*bus bars are what exist in UL's lab and are not a
requirement to perform this test
*UL's power panels this test is derived from will likely be
capable of very large fault currents, so they will add
resistance to limit the current
*a service entrance circuit breaker is not necessary; this
was chosen for it's larger interrupting rating, so as to not
degrade the breaker too quickly under repeated fault
conditions; you can use a plain old branch circuit breaker.


> 4.  The test circuit is connected to the DUT via
> the grounding lead of the
>   1.82 m (6 ft) power supply cord.  If cord
> is not provided, then #16 AWG
>   wire is used.

It's anyone's guess why a No. 16

> 5.  Test continues until ultimate results occur;
> e.g. CB trips, trace opens,
> etc.
>
> Carl

The preliminary testing I've performed in my lab indicates
that the fault portion of the test can be over very quickly
(probably ms, but I haven't tried to measure it), even with
No. 18 AWG conductors and four connectorized interfaces
involved.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com



This message is from the IEEE EMC Society Product Safety
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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[cnew...@xycom.com]

Lou,

It's my impression that the typical switching power supply, such as
that  used for ITE type equipment, will apply basic insulation between
the primary circuits and earthed conductive parts on the primary side.
They do this in order to minimize the creepage/clearance requirements
and subsequently reduce the size of the supply.  I'm referring specifically
to Tables 2G and 2F of 60950.

Thanks,
 Carl




From: "Lou Aiken"  on 02/03/2003 01:46 PM

To:   Carl Newton/XYCOM@XYCOM, emc-p...@majordomo.ieee.org
cc:

Subject:  Re: EN60950 protective conductor test (was Re: Circuit Breaker
  Tripping Dring Fault Tests)



Carl, If the primary supply circuitry and components provide double or
reinforced insulation, nothing can become live in the event of a single
fault, the test becomes unnecessary, and I would argue that fact.

If the design does not provide double or reinforced insulation, the test
sounds applicable from points that could become live in case of a basic
insulation fault.

Regards,
Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

tel ++ 1 251 981 6786
fax ++ 1 251 981 3054
Cell ++ 1 251 979 4648

From: 
To: 
Sent: Monday, February 03, 2003 11:19 AM
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)


>
>
>
> A slight divergence from the EN specifically, but I thought that the
> following would be helpful to this thread:
>
> I am presently working this issue with a UL engineer in accordance with
> UL 60950, 3rd Edition.   I also have the UL 60950 3rd Ed. Test Data
Sheets.
> Their "Protective Earthing Trace Earth Fault Current Test", UL Doc.
190.eng,
> per Section 2.6.3.3 requires the following in my case:
>
> 1.  Three samples are tested;
>
> 2.  Trace resistance is measured before and after test.  Resistance cannot
>   exceed 0.1 ohms, and cannot change more than 10% after test;
>
> 3.  AC source is 240 Vac, 200 amps (20A circuit breaker X 10), power
factor
>   is 75 - 80% through shorted bus bars with a 20/30 A (20 in my case)
> service
>   entrance type circuit breaker in series with the testing terminals.
The
> circuit
>   breaker is connected to the bus bars by 1.22 m (4 ft.) of #12 AWG
wire.
>
> 4.  The test circuit is connected to the DUT via the grounding lead of the
>   1.82 m (6 ft) power supply cord.  If cord is not provided, then #16
AWG
>   wire is used.
>
> 5.  Test continues until ultimate results occur; e.g. CB trips, trace
opens,
> etc.
>
> My UL guy tells me that I should expect the typical service type CB to be
rated
> up to  + 10%.  So it appears that  I need to concern myself with a burst
of
> current
> up to approximately 22 amps for the 20 amp AC circuit that my product is
being
> evaluated for.
>
> Carl
>
>
>
>
>
> From: "Chris Maxwell"  on 02/03/2003 09:29 AM
>
> Please respond to "Chris Maxwell" 
>
> To:   emc-p...@majordomo.ieee.org
> cc:(bcc: Carl Newton/XYCOM)
>
> Subject:  RE: EN60950 protective conductor test (was Re: Circuit Breaker
>   Tripping Dring Fault Tests)
>
>
>
>
> This thread has been interesting.  I am, at this moment, considering a
design
> where I am almost forced to use a PC (printed circuit) trace for Earth
ground.
>
> It seems funny to me that most equipment has been historically made with
18AWG
> protective ground pigtail wires; and 25A ground fault tests have been used
for
> years.
>
> Now that PC  traces are being used for protective ground; we want to test
with
> 200A or greater impulse currents?  I'm curious about what would happen to
your
> typical 18AWG line cord during this test.  I'm wondering if the line cord
would
> fuse open?
>
> There are a couple of handy charts on the web.
>
> One is at www.kepcopower.com/nomovax2.htm this is a nomograph of maximum
> operating current, AWG and IR drop in the conductor.  The point "A" is
generally
> considered the point of maximum IR drop.  If you draw a line from point
"A",
> through a wire gauge size; you'll get a max current.  Of course this is
steady
> state current; and the nomograph assumes a single wire.  Wire bundles
would be a
> worse case.  It's too bad that this chart doesn't contain the "fuse"
values for
> the wires as well (the  I squared * T values).
>
> Another is at www.circuitboards.com/capacity.php3.   This is a chart of
max
> current for PC traces.  Remember that this is for TRACES and planes only;
it
> doesn't say anything about vias and other potential problems.
>
> At first pass, it seems that a trace size to handle twice the power cord's
max
> current, (from the nomograph) with a 10degC trace temperature rise (

Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Lou Aiken]

Carl, If the primary supply circuitry and components provide double or
reinforced insulation, nothing can become live in the event of a single
fault, the test becomes unnecessary, and I would argue that fact.

If the design does not provide double or reinforced insulation, the test
sounds applicable from points that could become live in case of a basic
insulation fault.

Regards,
Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

tel ++ 1 251 981 6786
fax ++ 1 251 981 3054
Cell ++ 1 251 979 4648

From: 
To: 
Sent: Monday, February 03, 2003 11:19 AM
Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker
Tripping Dring Fault Tests)


>
>
>
> A slight divergence from the EN specifically, but I thought that the
> following would be helpful to this thread:
>
> I am presently working this issue with a UL engineer in accordance with
> UL 60950, 3rd Edition.   I also have the UL 60950 3rd Ed. Test Data
Sheets.
> Their "Protective Earthing Trace Earth Fault Current Test", UL Doc.
190.eng,
> per Section 2.6.3.3 requires the following in my case:
>
> 1.  Three samples are tested;
>
> 2.  Trace resistance is measured before and after test.  Resistance cannot
>   exceed 0.1 ohms, and cannot change more than 10% after test;
>
> 3.  AC source is 240 Vac, 200 amps (20A circuit breaker X 10), power
factor
>   is 75 - 80% through shorted bus bars with a 20/30 A (20 in my case)
> service
>   entrance type circuit breaker in series with the testing terminals.
The
> circuit
>   breaker is connected to the bus bars by 1.22 m (4 ft.) of #12 AWG
wire.
>
> 4.  The test circuit is connected to the DUT via the grounding lead of the
>   1.82 m (6 ft) power supply cord.  If cord is not provided, then #16
AWG
>   wire is used.
>
> 5.  Test continues until ultimate results occur; e.g. CB trips, trace
opens,
> etc.
>
> My UL guy tells me that I should expect the typical service type CB to be
rated
> up to  + 10%.  So it appears that  I need to concern myself with a burst
of
> current
> up to approximately 22 amps for the 20 amp AC circuit that my product is
being
> evaluated for.
>
> Carl
>
>
>
>
>
> From: "Chris Maxwell"  on 02/03/2003 09:29 AM
>
> Please respond to "Chris Maxwell" 
>
> To:   emc-p...@majordomo.ieee.org
> cc:(bcc: Carl Newton/XYCOM)
>
> Subject:  RE: EN60950 protective conductor test (was Re: Circuit Breaker
>   Tripping Dring Fault Tests)
>
>
>
>
> This thread has been interesting.  I am, at this moment, considering a
design
> where I am almost forced to use a PC (printed circuit) trace for Earth
ground.
>
> It seems funny to me that most equipment has been historically made with
18AWG
> protective ground pigtail wires; and 25A ground fault tests have been used
for
> years.
>
> Now that PC  traces are being used for protective ground; we want to test
with
> 200A or greater impulse currents?  I'm curious about what would happen to
your
> typical 18AWG line cord during this test.  I'm wondering if the line cord
would
> fuse open?
>
> There are a couple of handy charts on the web.
>
> One is at www.kepcopower.com/nomovax2.htm this is a nomograph of maximum
> operating current, AWG and IR drop in the conductor.  The point "A" is
generally
> considered the point of maximum IR drop.  If you draw a line from point
"A",
> through a wire gauge size; you'll get a max current.  Of course this is
steady
> state current; and the nomograph assumes a single wire.  Wire bundles
would be a
> worse case.  It's too bad that this chart doesn't contain the "fuse"
values for
> the wires as well (the  I squared * T values).
>
> Another is at www.circuitboards.com/capacity.php3.   This is a chart of
max
> current for PC traces.  Remember that this is for TRACES and planes only;
it
> doesn't say anything about vias and other potential problems.
>
> At first pass, it seems that a trace size to handle twice the power cord's
max
> current, (from the nomograph) with a 10degC trace temperature rise (from
the PC
> trace chart), would be a good rule of thumb for the trace size.  If I have
room,
> I'll just make it bigger.  Once we pay for the PC board fabrication, the
copper
> is free!
>
> Even with an  adequately sized trace; I can think of a few potential
problems
> with the trace to chassis connection:
>
> 1.  Many layout people open up PC traces or planes around vias so that
only four
> little 20 mil wide bridges carry the current to the via.  This is great
for
> soldering heat relief; but BAD for current carrying capacity.  These
little
> bridges can fuse open in high current conditions.  I am con

RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[cnew...@xycom.com]

A slight divergence from the EN specifically, but I thought that the
following would be helpful to this thread:

I am presently working this issue with a UL engineer in accordance with
UL 60950, 3rd Edition.   I also have the UL 60950 3rd Ed. Test Data Sheets.
Their "Protective Earthing Trace Earth Fault Current Test", UL Doc. 190.eng,
per Section 2.6.3.3 requires the following in my case:

1.  Three samples are tested;

2.  Trace resistance is measured before and after test.  Resistance cannot
  exceed 0.1 ohms, and cannot change more than 10% after test;

3.  AC source is 240 Vac, 200 amps (20A circuit breaker X 10), power factor
  is 75 - 80% through shorted bus bars with a 20/30 A (20 in my case)
service
  entrance type circuit breaker in series with the testing terminals.  The
circuit
  breaker is connected to the bus bars by 1.22 m (4 ft.) of #12 AWG wire.

4.  The test circuit is connected to the DUT via the grounding lead of the
  1.82 m (6 ft) power supply cord.  If cord is not provided, then #16 AWG
  wire is used.

5.  Test continues until ultimate results occur; e.g. CB trips, trace opens,
etc.

My UL guy tells me that I should expect the typical service type CB to be rated
up to  + 10%.  So it appears that  I need to concern myself with a burst of
current
up to approximately 22 amps for the 20 amp AC circuit that my product is being
evaluated for.

Carl





From: "Chris Maxwell"  on 02/03/2003 09:29 AM

Please respond to "Chris Maxwell" 

To:   emc-p...@majordomo.ieee.org
cc:(bcc: Carl Newton/XYCOM)

Subject:  RE: EN60950 protective conductor test (was Re: Circuit Breaker
  Tripping Dring Fault Tests)




This thread has been interesting.  I am, at this moment, considering a design
where I am almost forced to use a PC (printed circuit) trace for Earth ground.

It seems funny to me that most equipment has been historically made with 18AWG
protective ground pigtail wires; and 25A ground fault tests have been used for
years.

Now that PC  traces are being used for protective ground; we want to test with
200A or greater impulse currents?  I'm curious about what would happen to your
typical 18AWG line cord during this test.  I'm wondering if the line cord would
fuse open?

There are a couple of handy charts on the web.

One is at www.kepcopower.com/nomovax2.htm this is a nomograph of maximum
operating current, AWG and IR drop in the conductor.  The point "A" is
generally
considered the point of maximum IR drop.  If you draw a line from point "A",
through a wire gauge size; you'll get a max current.  Of course this is steady
state current; and the nomograph assumes a single wire.  Wire bundles would be
a
worse case.  It's too bad that this chart doesn't contain the "fuse" values for
the wires as well (the  I squared * T values).

Another is at www.circuitboards.com/capacity.php3.   This is a chart of max
current for PC traces.  Remember that this is for TRACES and planes only; it
doesn't say anything about vias and other potential problems.

At first pass, it seems that a trace size to handle twice the power cord's max
current, (from the nomograph) with a 10degC trace temperature rise (from the PC
trace chart), would be a good rule of thumb for the trace size.  If I have
room,
I'll just make it bigger.  Once we pay for the PC board fabrication, the copper
is free!

Even with an  adequately sized trace; I can think of a few potential problems
with the trace to chassis connection:

1.  Many layout people open up PC traces or planes around vias so that only
four
little 20 mil wide bridges carry the current to the via.  This is great for
soldering heat relief; but BAD for current carrying capacity.  These little
bridges can fuse open in high current conditions.  I am considering solving
this
by not putting any thermal reliefs around your Earth ground vias and using
multiple vias.

2.  Another problem with these traces is using plated through vias with screws
through them.It has been found that plated through vias can crack when they
are put under pressure from screws.Some power supply manufacturers solve
this by bringing the Earth ground trace to the surface with vias near the
chassis connection point; then route this to a solid plated pad on the surface
layer for chassis connection.  I am considering this same solution as well.

3.  The third problem is mechanical.  Once Earth ground brought to a pad on the
circuitboard; then there is still the issue of getting a good mechanical mate
to
the chassis with a wide surface area.  If the connection is made through a
couple of teeth on a star washer; then there is a potential for localized
heating.   I'm just going to maximize surface contact area for this one.  I'm
also considering using multiple board to chassis connection locations.  Every
screw that connects the board to chassis is a potential Earth

RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[Chris Maxwell]

This thread has been interesting.  I am, at this moment, considering a design
where I am almost forced to use a PC (printed circuit) trace for Earth ground.

It seems funny to me that most equipment has been historically made with 18AWG
protective ground pigtail wires; and 25A ground fault tests have been used for
years.  

Now that PC  traces are being used for protective ground; we want to test with
200A or greater impulse currents?  I'm curious about what would happen to your
typical 18AWG line cord during this test.  I'm wondering if the line cord
would fuse open? 

There are a couple of handy charts on the web.

One is at www.kepcopower.com/nomovax2.htm this is a nomograph of maximum
operating current, AWG and IR drop in the conductor.  The point "A" is
generally considered the point of maximum IR drop.  If you draw a line from
point "A", through a wire gauge size; you'll get a max current.  Of course
this is steady state current; and the nomograph assumes a single wire.  Wire
bundles would be a worse case.  It's too bad that this chart doesn't contain
the "fuse" values for the wires as well (the  I squared * T values).

Another is at www.circuitboards.com/capacity.php3.   This is a chart of max
current for PC traces.  Remember that this is for TRACES and planes only; it
doesn't say anything about vias and other potential problems.  

At first pass, it seems that a trace size to handle twice the power cord's max
current, (from the nomograph) with a 10degC trace temperature rise (from the
PC trace chart), would be a good rule of thumb for the trace size.  If I have
room, I'll just make it bigger.  Once we pay for the PC board fabrication, the
copper is free!

Even with an  adequately sized trace; I can think of a few potential problems
with the trace to chassis connection:

1.  Many layout people open up PC traces or planes around vias so that only
four little 20 mil wide bridges carry the current to the via.  This is great
for soldering heat relief; but BAD for current carrying capacity.  These
little bridges can fuse open in high current conditions.  I am considering
solving this by not putting any thermal reliefs around your Earth ground vias
and using multiple vias.

2.  Another problem with these traces is using plated through vias with screws
through them.It has been found that plated through vias can crack when
they are put under pressure from screws.Some power supply manufacturers
solve this by bringing the Earth ground trace to the surface with vias near
the chassis connection point; then route this to a solid plated pad on the
surface layer for chassis connection.  I am considering this same solution as
well.

3.  The third problem is mechanical.  Once Earth ground brought to a pad on
the circuitboard; then there is still the issue of getting a good mechanical
mate to the chassis with a wide surface area.  If the connection is made
through a couple of teeth on a star washer; then there is a potential for
localized heating.   I'm just going to maximize surface contact area for this
one.  I'm also considering using multiple board to chassis connection
locations.  Every screw that connects the board to chassis is a potential
Earth ground connection.

The last "fuse" in any power system is the cord connected to the product.  It
seems to me, (just an opinion now) that a Earth ground system made to handle
the worst case current of your worst case power input cable (along with some
design margin) would stand a good chance of passing any regulatory test.  

Can any of the gurus see a problem with this?

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797 8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 







This message is from the IEEE EMC Society Product Safety
Technical Committee emc-pstc discussion list.

Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/

To cancel your subscription, send mail to:
 majord...@ieee.org
with the single line:
 unsubscribe emc-pstc

For help, send mail to the list administrators:
 Ron Pickard:  emc-p...@hypercom.com
 Dave Heald:   davehe...@attbi.com

For policy questions, send mail to:
 Richard Nute:   ri...@ieee.org
 Jim Bacher: j.bac...@ieee.org

Archive is being moved, we will announce when it is back on-line.
All emc-pstc postings are archived and searchable on the web at:
http://www.ieeecommunities.org/emc-pstc

Re: EN60950 protective conductor test

[Lou Aiken]

I support both John's opinions.

I don't want PC traces for PE circuits outlawed in the standards because
there may be some valid reason to do that, but I have never come across it
in ITE or domestic appliances.

Based on my experience all mains circuits are provided with double or
reinforced insulation. I believe the cost hit for that construction can be
essentially nothing.

Consequently nothing is connected to the so-called PE trace (or more
correctly, a PC trace connected to the product's earthing means) except the
approved Y caps, and possibly one or more SELV circuits.

When inexperienced test engineers mentioned high current withstand of  PC
traces, I  point out that the mains circuits cannot fault to earthed
circuits as a result of a single fault.  Therefore, the test is not
required.

Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

tel ++ 1 251 981 6786
fax ++ 1 251 981 3054
Cell ++ 1 251 979 4648

From: John Woodgate 
To: 
Sent: Saturday, February 01, 2003 3:12 PM
Subject: Re: EN60950 protective conductor test


>
> I read in !emc-pstc that Rich Nute  wrote (in
> <200302012030.maa04...@epgc264.sdd.hp.com>) about 'EN60950 protective
> conductor test' on Sat, 1 Feb 2003:
> >>   short-circuit conditions. The printed-board mounting versions of the
IEC
> >>   60320 appliance connector encourage the use of board traces to carry
the
> >>   PEC; something that I would not be happy about, in principle.
> >
> >Such construction cannot be sloughed off in such
> >an off-hand manner.  This is solo BOGSAT
> >engineering, which cannot be condoned.
>
> Is it not permitted to express a personal preference on this group? I
> *prefer, personally*, not to use printed board traces as parts of the
> PEC. I'm not suggesting that should be in IEC 60950 or any other
> standard.
> --
> Regards, John Woodgate, OOO - Own Opinions Only.
http://www.jmwa.demon.co.uk
> Interested in professional sound reinforcement and distribution? Then go
to
> http://www.isce.org.uk
> PLEASE do NOT copy news posts to me by E-MAIL!
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
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Re: EN60950 protective conductor test

[John Woodgate]

I read in !emc-pstc that Rich Nute  wrote (in
<200302012030.maa04...@epgc264.sdd.hp.com>) about 'EN60950 protective
conductor test' on Sat, 1 Feb 2003:
>>   short-circuit conditions. The printed-board mounting versions of the IEC
>>   60320 appliance connector encourage the use of board traces to carry the
>>   PEC; something that I would not be happy about, in principle. 
>
>Such construction cannot be sloughed off in such
>an off-hand manner.  This is solo BOGSAT 
>engineering, which cannot be condoned.

Is it not permitted to express a personal preference on this group? I
*prefer, personally*, not to use printed board traces as parts of the
PEC. I'm not suggesting that should be in IEC 60950 or any other
standard.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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Re: EN60950 protective conductor test

[Rich Nute]

This message has been converted via the evaluation version of
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-




Hi John:


>   short-circuit conditions. The printed-board mounting versions of the IEC
>   60320 appliance connector encourage the use of board traces to carry the
>   PEC; something that I would not be happy about, in principle. 

Such construction cannot be sloughed off in such
an off-hand manner.  This is solo BOGSAT 
engineering, which cannot be condoned.

Rather, the scientific method must be applied so
as to reach a conclusion that has a foundation
supporting the conclusion.

1.  Statement of the problem.  

Board traces to a board-mounted IEC 60320 
applicance connector cannot withstand the
prospective short-circuit current.

2.  Hypothesis as to the cause of the problem.

The cross-sectional area of the connection 
from the board trace to the 60320 connector 
is insufficient to withstand the prospective
short-circuit current.

3.  Experiments designed to test the hypothesis.

Design a set of boards with different 
cross-sectional areas of the connection of
the board to the 60320 connector.  Apply the
test to each board.

4.  Predicted results of the experiments.

Where the cross-sectional area equals or
exceeds that of the supply conductors, the
connection will not fail.

5.  Observed results of the experiments.

TBD

6.  Conclusions of the experiments.

TBD

"The real purpose of the scientific method is to 
make sure that Nature hasn't misled you into
thinking you know something you don't actually 
know."  -- Robert M. Persig, Zen and the Art of
Motorcycle Maintenance.


Best regards,
Rich






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Re: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests)

[John Woodgate]

I read in !emc-pstc that Nick Williams 
wrote (in ) about 'EN60950
protective conductor test (was Re: Circuit Breaker Tripping Dring Fault
Tests)' on Fri, 31 Jan 2003:
>
>At 12:22 + 31/1/03, John Woodgate wrote:
>>
>>There is a proposed amendment to IEC/EN 60950-1 requiring a test of the
>>protective conductor network at *prospective short-circuit current* for
>>the time it takes for the mains circuit protective device to operate.
>>The details are controversial at present, because the test currents
>>appear not to have taken into account the differences between
>>prospective short-circuit currents in different wiring systems and
>>supply voltages. Given that reservation, the lowest test current is 200
>>A.
>>
>>The amendment is aimed at protective conductors which are surface or
>>internal traces of multi-layer printed boards. It is said that such
>>traces have failed in the field under high-current fault conditions.
>>--
>
>Is the proposal to replace the existing test in the standard or to 
>add an additional  test only for certain special circumstances?

It's additional.
>
>Is there any evidence that this test would actually result in a 
>significant number of poorly designed products which currently pass 
>the requirements of the standard being rejected?

This is the claimed justification for the introduction. Field problems
have occurred where printed board conductors have failed in high-current
short-circuit conditions. The printed-board mounting versions of the IEC
60320 appliance connector encourage the use of board traces to carry the
PEC; something that I would not be happy about, in principle. 
>
>The existing test has its faults but it is easy to do with some very 
>cheap apparatus. It strikes me that the cost of doing a test at 200+A 
>is potentially very substantial. 

I don't think 200 A is too much of a problem, but testing at higher
currents is proposed for some equipment. I don't want to be too
explicit, because the figures in the draft are highly suspect (of
applying to 120 V supplies!).

>If the result of an amendment to the 
>standard is that significant numbers of self-certified products which 
>have not been properly tested in this aspect of their design reach 
>the market, then the net result will actually be a significant 
>reduction in the safety of end users.

I don't understand that. You mean that if people cheat, safety will be
compromised? That's always the case. But in fact, the presence of the
test may well concentrate attention on the need to make such traces
substantial, whether they are tested or not.
>
>A cynic's view might also be that an amendment of this nature would 
>suit the test labs and larger manufacturers fine, since they will be 
>able to justify the cost of the apparatus required, whereas smaller 
>manufacturers (and yes, small consultancy companies like mine) will 
>not.
Remember you don't necessarily need 200 A at 230 V. I can get 200 A at a
bit over 1 V from a single turn on a big toroidal transformer.
>
>OK, I admit I'm putting two and two together and getting about seven 
>but I believe one should get one's retaliation in first in these 
>circumstances! Any amendment along the lines suggested should be 
>prepared to sacrifice a fair degree of technical accuracy against the 
>need for the test to be cheap, quick and easy to perform.

It doesn't call for technical accuracy. You zap the equipment with the
200 A current for the operating time of the protective device and the
PEC either remains intact or doesn't.
>
>Nowadays, standards writing should not just about getting accuracy 
>and repeatability in testing but should also take into account the 
>need to ensure that the requirements (and hence the tests) are 
>actually possible to apply in the real world, and not just by people 
>at specialist test houses.
>
I quite agree, but as you indicate above, there isn't too much *active*
support for that view. When I talk in the committees about low-cost
testing, people tend to remain silent. In any case, at present it's
difficult enough coping with the problems of the costly test equipment
not measuring correctly or not being feasible (low-distortion, high-
current mains supplies for IEC 61000-3-12, as a case in point).

If you want a copy of the draft, to make comments to the BSI committee,
please e-mail. Note that this offer can only be made to people in UK.
Others should approach their national standards body.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!


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Re: EN60950 protective conductor test (was Re: Circuit Breaker

[Rich Nute]

Hi Nick:


>   >There is a proposed amendment to IEC/EN 60950-1 requiring a test of the
>   >protective conductor network at *prospective short-circuit current* for
>   >the time it takes for the mains circuit protective device to operate.
>   >The details are controversial at present, because the test currents
>   >appear not to have taken into account the differences between
>   >prospective short-circuit currents in different wiring systems and
>   >supply voltages. Given that reservation, the lowest test current is 200
>   >A.
>   >
>   >The amendment is aimed at protective conductors which are surface or
>   >internal traces of multi-layer printed boards. It is said that such
>   >traces have failed in the field under high-current fault conditions.
>   >--

Before we proceed with such a test, we must first
determine 

1-  where basic insulation could fail to a grounded 
part;

2-  the impedance of the failure, which must be less 
than that of the source impedance (otherwise, 
the fault itself limits the current);

3-  the path from the point of the fault as only this
path need be tested (not all ground circuit paths 
are subject to a basic insulation fault and there-
fore are not subject to the test).

>   Is the proposal to replace the existing test in the standard or to 
>   add an additional  test only for certain special circumstances?
>   
>   Is there any evidence that this test would actually result in a 
>   significant number of poorly designed products which currently pass 
>   the requirements of the standard being rejected?

Yes.

Having done this test, a conventional PWB ground path 
that passes the 25-amp, 2-minute test MAY not pass 
this test.

A PWB ground path will pass the test if the cross-
sectional area of the trace and its connections is
equal the cross-sectional area of the required 
ground wire.

>   The existing test has its faults but it is easy to do with some very 
>   cheap apparatus. It strikes me that the cost of doing a test at 200+A 
>   is potentially very substantial. If the result of an amendment to the 
>   standard is that significant numbers of self-certified products which 
>   have not been properly tested in this aspect of their design reach 
>   the market, then the net result will actually be a significant 
>   reduction in the safety of end users.

In reality, basic insulation seldom fails.  

If the basic insulation does fail, the failure is 
likely to be a point-contact, not a large-area 
contact.  A point contact is a relatively high 
resistance, and limits the current.

The basic idea of the test is valid.  However, it
may be superfluous and inappropriate for practical
application in many kinds of electronic equipment.

>   A cynic's view might also be that an amendment of this nature would 
>   suit the test labs and larger manufacturers fine, since they will be 
>   able to justify the cost of the apparatus required, whereas smaller 
>   manufacturers (and yes, small consultancy companies like mine) will 
>   not.

The apparatus is quite simple.  I would guess that
many labs, if they do high-power testing, already 
have the necessary equipment.

>   OK, I admit I'm putting two and two together and getting about seven 
>   but I believe one should get one's retaliation in first in these 
>   circumstances! Any amendment along the lines suggested should be 
>   prepared to sacrifice a fair degree of technical accuracy against the 
>   need for the test to be cheap, quick and easy to perform.
>   
>   Nowadays, standards writing should not just about getting accuracy 
>   and repeatability in testing but should also take into account the 
>   need to ensure that the requirements (and hence the tests) are 
>   actually possible to apply in the real world, and not just by people 
>   at specialist test houses.

Well... I would state this a bit differently.  A
standards-writing organization should apply the
scientific method to all new requirements.  


Best regards,
Rich





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Re: EN60950:2000 & EN60950-1 last dates of manufacture

[John Woodgate]

I read in !emc-pstc that Peter L. Tarver 
wrote (in )
about 'EN60950:2000 & EN60950-1 last dates of manufacture' on Tue, 12
Nov 2002:

>It would be a good thing (tm) if Subclause 4.5 of the Guide
>to the Implementation of Directives Based on New Approach
>and Global Approach (Blue Guide) made such a clear and
>unambiguous statement.  Perhaps you can make this
>recommendation to your acquaintance.

In my report to the group, I included a quote from my e-mail thanking my
contact for his response, saying that the Commission should publish a
document about the meaning of docopocoss.

He has now replied that he has forwarded the proposal to the Commission.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Peter L. Tarver]

John -

Thank you for taking this up with your acquaintance.

FWIW, I've been involved in product safety for more than 18
years, the last 10 of which have had increasingly global
scope.  Though perhaps to a lifer, I'm a wee babe just out
of my nappies. ;)

The crux of your acquaintance's reply is that:

1) if the manufacturer resides in the EU, the docopocoss
applies to the last date a product may be shipped from the
factory;

2) if the manufacturer does not reside in the EU, the
docopocoss is the date shipped from the importer's (or
authorized representative's) facility.

So, stock may not be held on shelves at any location prior
to the *external* distribution chain, regardless of date of
manufacture, shipped after the docopocoss and be considered
in compliance with applicable EU Directives, if a superceded
standard was used as a basis for conformity.

There may be some stickiness with respect to who is
considered a distributor, if, for instance Inchcape, Thomson
or some other large distributor is also the importer, but
this can no doubt be handled by dummy corporations at an
adjacent store front, tent, awning or back alley address
(all appropriate permits and licenses in place, of course)
serving as the importer.  Similar "iffyness" exists if the
importer/distributor is the owner of the manufacturing plant
located outside the EU or if the importer/distributor is
owned by the same parent company as the manufacturer.

I have a query in with the EC, which (I was informed this
morning) won't be answered until next week, due to a trade
mission to Asia.

I can't help but snicker that the EC were determined to
remove the legislative purview  from CENELEC (as previously
posted) in assigning the docopocoss (in their standard's
forwards as a last date of manufacture), that a reference
would be given back to a CENELEC Guide to explain the EC's
intent.  O. Henry would be pleased.

It would be a good thing (tm) if Subclause 4.5 of the Guide
to the Implementation of Directives Based on New Approach
and Global Approach (Blue Guide) made such a clear and
unambiguous statement.  Perhaps you can make this
recommendation to your acquaintance.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com



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Re: EN60950:2000 & EN60950-1 last dates of manufacture

[John Woodgate]

I read in !emc-pstc that John Woodgate  wrote (in
) about 'EN60950:2000 & EN60950-1
last dates of manufacture' on Tue, 5 Nov 2002:

I addressed this question to Peter Tarver, who replied by -email that he
definitely needs an *official* document 

>Exactly what is still bugging you? I would have thought that everything
>in doubt or obscure had already been explained.

I know of no official document, so I asked someone in Brussels who would
DEFINITELY know of such a document or could provide a better explanation
that I could. You will understand that I am not in a position to say
whom I asked, but this is as authoritative as you can get, IMHO.

This is what I sent and the reply I received:

QUOTE

ENQUIRY/QUESTION

I am trying to find an official Commission or Council document that
explains or defines exactly what the 'date of cessation of presumption
of conformity of the superseded standard' actually means. 

As new, younger people come into the EMC and safety standards field,
some of the facts that are well understood and accepted by those of us
who have ten or more years involvement are being challenged and
documentary proof is being demanded. This is not unreasonable, because
guesses and folklore are still creating confusion.

In this particular case, the 'docopocoss' could be (in the minds of
people new to the subject):

- 1) the last date at which a product conforming only to the old
standard may be manufactured;

-2) the last date on which it may be shipped from the manufacturer's
premises to a distributor, retailer or end-user;

- 3) the last date that may appear on an invoice for the product;

- 4) the last date on which it may be sold to an end-user by a
distributor or retailer;

- 5) the last date on which it may be 'taken into service'.

The fact that they demand reliable official information can be
appreciated.
-- 

ANSWER

I found the following definitions on the Web site of the Commission 
(http://europa.eu.int/comm/enterprise). Guide 25 of CENELEC is also very
useful to be looked at (available on CENELEC web site)

What does "Date of cessation [of presumption of conformity of the
superseded standard]" mean? 

A product compliant with a given standard and placed on the market (see
definition in section 2.3 of the Guide to the Implementation of
Directives Based on New Approach and Global Approach) after the 
"date of cessation" of this standard will not enjoy presumption of
conformity with the requirement of the EMC directive. 

My product enjoys presumption of conformity through compliance with
standard "S", whose date of cessation is 01/01/2003. It is replaced by
standard "T". What does it mean practically for my product ?
 
The EMC Directive concerns the time of the placing on the market or
putting into service of each individual apparatus.

- Each individual apparatus placed on the market before 01/01/2003 will
enjoy presumption of conformity if they comply either with standard "S"
or standard "T".

- Each individual apparatus placed on the market after 01/01/2003 will
enjoy presumption of conformity only if they comply standard "T". 

The key point is thus the definition (plus comments) of 'placing on the
market' as given in the New approach (see guide quoted above or
Commission EMC guide 1997,clause 3.1, available on Commission web site):

'This means first making available, against payment or free of charge,
an apparatus in the EEA market for the purpose of distribution and /or
use in the EEA'. Among the 5 options given in your enquiry, the options
1), and 3) are thus not relevant.

For normal ready-made products for general use, options 5) and 4) are
normally not applicable and thus option 2) is generally the closest to
the definition of placing on the market for those products, except that
for products manufactured outside the EEA, 'manufacturer 
premises' is replaced by the 'importer or authorised representative in
the EEA.

ENDQUOTE

In thanking my source for the information, I have added:

It is important that manufacturers and importers clearly understand the
matter, and it is clear from messages on the IEEE 'compliance' mailgroup
that misunderstanding is widespread. 

I would therefore suggest that a 'semi-official' document (i.e. of the
same status as the 'EMC Guidelines') on the subject should be published
by the Commission.

It is true that 'anyone' could have found the information that you very
kindly provided, but 'anyone' would not know for certain where to look,
and, more important, would not know if **all relevant** information had
been obtained.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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Re: EN60950:2000 & EN60950-1 last dates of manufacture

[John Woodgate]

I read in !emc-pstc that Peter L. Tarver 
wrote (in )
about 'EN60950:2000 & EN60950-1 last dates of manufacture' on Tue, 5 Nov
2002:

>"Note 1: Generally the date of cessation of presumption of
>conformity will be the date of withdrawal (‘dow’), set by
>the European Standardisation Organisation, but attention of
>users of these standards is drawn to the fact that in
>certain exceptional cases this can be otherwise."
>
>I suppose this is how/why CENELEC put dates in their
>versions of EN60950 (and possibly others) in the first
>place, or perhaps Note 1 was included to accommodate
>CENELEC's  habits.  It may be that Note 1 will disappear as
>the EC has their way and older editions of standards scroll
>off the list.

The history is that originally there was just the dow determined by
CENELEC. But then the Commission's lawyers decided to justify their
existence by point out that that made the dow *regulatory*, not
*standardization* and insisted that the Commission set the docopocoss
quite independently of CENELEC. That wasn't acceptable to industry, so
the compromise was that NORMALLY the Commission will accept the dow for
the docopocoss, but formally reserves the right to set a different date.

>
>I am still dicing the finer points of language.  I will
>report back whatever I might find and hope that anyone with
>official and unambiguous information related to this query
>will step forward.

Exactly what is still bugging you? I would have thought that everything
in doubt or obscure had already been explained.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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Re: EN60950:2000 & EN60950-1 last dates of manufacture

[John Woodgate]

I read in !emc-pstc that Peter L. Tarver 
wrote (in )
about 'EN60950:2000 & EN60950-1 last dates of manufacture' on Tue, 5 Nov
2002:
>Yes, I have tried speaking with a NB (one of the NCBs I
>mentioned is also an NB under certain of the Directives).

Well, did you get any useful response?
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Richard Hughes]

Peter,

The note you are referring to is in the OJEC.  If you wanted to paraphrase
it, one option would be "We (the Commission) have the responsibility for
directives and not you (CENELEC).  Therefore, we'll set the Date of
Cessation to be equal to the Date of Withdrawal providing that we can be
convinced that the date is correct."  I seem to recall that Dates of
Cessation have been changed from one version of the OJEC and the next
(following discussions in the CENELEC BT) as regards safety standards.  Life
has been even more 'interesting' as regards EMC standards.

Regards

Richard Hughes.

 
-Original Message-
From: Peter L. Tarver [mailto:peter.tar...@sanmina-sci.com]
Sent: 05 November 2002 15:21
To: emc-p...@majordomo.ieee.org
Cc: Hughes, Richard [HAL02:GF00:EXCH]
Subject: RE: EN60950:2000 & EN60950-1 last dates of manufacture


Richard -

You will also note that Note 1 of the list of harmonized
standards states:

"Note 1: Generally the date of cessation of presumption of
conformity will be the date of withdrawal ('dow'), set by
the European Standardisation Organisation, but attention of
users of these standards is drawn to the fact that in
certain exceptional cases this can be otherwise."

I suppose this is how/why CENELEC put dates in their
versions of EN60950 (and possibly others) in the first
place, or perhaps Note 1 was included to accommodate
CENELEC's  habits.  It may be that Note 1 will disappear as
the EC has their way and older editions of standards scroll
off the list.

I am still dicing the finer points of language.  I will
report back whatever I might find and hope that anyone with
official and unambiguous information related to this query
will step forward.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com

-Original Message-
From: Richard Hughes [mailto:rehug...@nortelnetworks.com]


Peter,


The reason for the removal of the so-called 'certification
clause' that was in the Foreword of the various amendments
to EN 60950:1992 but is not in the Forward to EN 60950:2000
and EN 60950-1:2002 is as follows:

- There was a request from the Commission to remove this
text from all standards referenced in the OJEC under the
LVD.  I have not tried to find the exact text but I can
imagine that those who wish to look for it would need access
to documents from the CENELEC Technical Board (CENELEC BT).

- Although I do not have all the list of standards published
in the OJEC in relation to the LVD, I do recall that it was
not always the case that the list had the column entitled
"Date of cessation of presumption of conformity of the
superseded standard  Note 1".  The first version of the
revised list I have stored on my PC is dated 1999 (but this
may not be the first such list).  Nevertheless, you can see
that there would be confusion if a standard were to give one
date and the OJEC were to give another date.  Eliminating
the 'certification clause' leaves the OJEC as the only date
for the expiree of a standard, with the Commission being in
overall control of when that date is (although in practice
this would normally be agreed with the CENELEC BT).

RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Peter L. Tarver]

Richard -

You will also note that Note 1 of the list of harmonized
standards states:

"Note 1: Generally the date of cessation of presumption of
conformity will be the date of withdrawal (‘dow’), set by
the European Standardisation Organisation, but attention of
users of these standards is drawn to the fact that in
certain exceptional cases this can be otherwise."

I suppose this is how/why CENELEC put dates in their
versions of EN60950 (and possibly others) in the first
place, or perhaps Note 1 was included to accommodate
CENELEC's  habits.  It may be that Note 1 will disappear as
the EC has their way and older editions of standards scroll
off the list.

I am still dicing the finer points of language.  I will
report back whatever I might find and hope that anyone with
official and unambiguous information related to this query
will step forward.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com

-Original Message-
From: Richard Hughes [mailto:rehug...@nortelnetworks.com]


Peter,


The reason for the removal of the so-called 'certification
clause' that was in the Foreword of the various amendments
to EN 60950:1992 but is not in the Forward to EN 60950:2000
and EN 60950-1:2002 is as follows:

- There was a request from the Commission to remove this
text from all standards referenced in the OJEC under the
LVD.  I have not tried to find the exact text but I can
imagine that those who wish to look for it would need access
to documents from the CENELEC Technical Board (CENELEC BT).

- Although I do not have all the list of standards published
in the OJEC in relation to the LVD, I do recall that it was
not always the case that the list had the column entitled
"Date of cessation of presumption of conformity of the
superseded standard  Note 1".  The first version of the
revised list I have stored on my PC is dated 1999 (but this
may not be the first such list).  Nevertheless, you can see
that there would be confusion if a standard were to give one
date and the OJEC were to give another date.  Eliminating
the 'certification clause' leaves the OJEC as the only date
for the expiree of a standard, with the Commission being in
overall control of when that date is (although in practice
this would normally be agreed with the CENELEC BT).




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RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Peter L. Tarver]

Thank you, Richard; an illuminating script.  Thank you,
also, to all those that have replied to me, on and off the
list.


The crux of my present situation is this: we have a customer
that is claiming "relief" from having to comply with the
next edition of the standard and is citing an excerpt from
the list of harmonized standards as the basis of this
conclusion.  My research and query efforts are intended to
make certain this customer is kept "clean" and that they are
not making a poorly informed business decision.

If I am to make the case that they *must* comply with the
later edition of a standard, I need something beyond opinion
and speculation.  This customer has been stung in the past
by (others) not using the latest standard edition for their
product certifications and are particularly sensitive to the
cost of certifications.  Hence, my doggedness in insisting
upon official documentation in support of any interpretation
with respect to intent of the changes in the Forwards of
harmonized standards and meaning of text in the list of
harmonized standards.



Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com



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RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Peter L. Tarver]

John -

Yes, I have tried speaking with a NB (one of the NCBs I
mentioned is also an NB under certain of the Directives).


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com

> From: John Woodgate
>
> Peter L. Tarver wrote:
> >is there an
> >official document available that provides unambiguous
> >clarity defining "date of cessation of presumption of
> >conformity of the superseded standard," in the context of
> >manufacturing?
>
>  Have
> you tried asking the DTI
> or a Notified Body?


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RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Richard Hughes]

3 states "Technical documentation must enable
the conformity of the electrical equipment to the requirements of this
Directive to be assessed." and in the 4th indent "a list of the standards
applied in full or in part, and descriptions of the solutions adopted to
satisfy the safety aspects of this Directive where standards have not been
applied".  So, it is necessary (when using standards) to both maintain
compliance of your product with the applicable standards referenced in the
OJEC and also to update your technical files with this fact.

In summary, if the LVD applies to your product and you wish to use
harmonised standards to show that each and every item rolling off your
production line complies then ensure your product complies with a version of
the standard that has not gone beyond its 'date of cessation'. If you wish
to show compliance with the 'safety objectives' directly, then forget
standards and dates of cessation.

Naturally these are just personal opinions and I am not a lawyer: if you
make a product decision based on the above then on your own head be it.

Regards,

Richard Hughes.


-Original Message-
From: Peter L. Tarver [mailto:peter.tar...@sanmina-sci.com]
Sent: 04 November 2002 20:20
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950:2000 & EN60950-1 last dates of manufacture



All -

I have received a number of responses, for which I am
grateful.

As a matter of course, we must all try to act as lawyers in
pursuit of compliance.  To that end, I reviewed the
documents I had in hand [which included the CSA transition
document (which I treat as a third hand interpretation), the
LVD, the list of harmonized standards from the OJ, the Guide
to the Implementation of Directives Based on New Approach
and Global Approach, EN60950:1992 through A4 and a copy of
the Forward to EN60950:2000], prior to posting my query.
None of these provided me with a feeling of certain
knowledge.


As points of comparison, I offer the following citations.

>From Guide to the Implementation of Directives Based on New
Approach and Global Approach (the so-called "Blue Guide"):

"4.5. Revision of harmonised standards

"Following its internal regulations, the relevant European
standard organisation lays down the date of publication at
national level of the revised harmonised standard, and the
date of withdrawal of the old standard. The transitional
period is normally the time period between these two dates.
During this transitional period both harmonised standards
give presumption of conformity, provided that the conditions
for this are met. After this transitional period, only the
revised harmonised standard gives a presumption of
conformity.

"The Commission may consider that, for safety or other
reasons, the old version of the harmonised standard must
cease giving a presumption of conformity before its date of
withdrawal, set by European standards organisation in
question. In such cases, the Commission fixes an earlier
date after which the standard will no longer give a
presumption of conformity, and publishes this information in
the Official Journal. If circumstances allow, the Commission
consults the Member States prior to taking a decision to
reduce the period during which the standard gives a
presumption of conformity.

"The reference of the revised harmonised standard, the
reference of the old harmonised standard, and the date where
the presumption of conformity of the old standard finishes
are published together in the Official Journal."

>From EN60950:1992, Forward to A4:

"For products which have complied with EN 60950:1992 and its
amendments A1:1993, A2:1993, A3:1995 before 1998-08-01, as
shown by the manufacturer or by a certification body, this
previous standard may continue to apply for production until
2003-08-01."

You will note that there is a distinct difference in
language between the two documents.  EN60950:1992 is quite
clear, while the Blue Guide is not quite satisfying.

Other points of comparison lie in the last dates of
manufacture in the various forwards EN60950:1992 and the
right-most column from the OJ's list of harmonized standards
titled  "Date of cessation of presumption of conformity of
the superseded standard."  These dates agree completely,
though I still wished to eliminate all doubt, because of the
differences in language.  The language of the list of
harmonized standards and the Blue Guide don't explicitly
mention manufacturing and could be interpreted as the last
date a product certification could be obtained using a
standard, which is consistent with the text of the forwards
to EN60950:1992.

With the absence of similar verbiage in the forward to
EN60950:2000 and knowing that the last dates of manufacture
in EN60950:1992 occurred some time after the DOW for each
amendment, I am left desirous of certainty.  With the advent
of an additional interpretation (I 

Re: EN60950:2000 & EN60950-1 last dates of manufacture

[John Woodgate]

I read in !emc-pstc that Peter L. Tarver 
wrote (in )
about 'EN60950:2000 & EN60950-1 last dates of manufacture' on Mon, 4 Nov
2002:
>I now wish to change my query, to alleviate the irritation
>some may have felt at this being "asked again": is there an
>official document available that provides unambiguous
>clarity defining "date of cessation of presumption of
>conformity of the superseded standard," in the context of
>manufacturing? 

Look at it this way. You are not allowed to send out from the factory a
non-conforming product. A product conforming to a standard but made
after its docopocoss is ipso facto *non-conforming* unless it also
conforms to the superseding standard. 

The control of products that are in the distribution chain is a matter
for individual member states. It is unlikely that in the normal course
of evolution of a standard that the regulatory authorities would take
action against a limited number of products in the supply chain. Cui
bono?

However, if the Commission considered that an old standard was
sufficiently unsatisfactory to justify an earlier docopocoss than the
dow, or if a regulatory authority found large stocks of old product
still unsold after a reasonable time (such as one year) for such stock
to be cleared, action might then follow. This is how the matter was
handled in most countries when the EMC Directive came into effect, and
it seems unlikely that the procedure would change for no good reason. I
think this was explained in one of the DTI publications prior to the EMC
Directive introduction, but I'm not sure. Have you tried asking the DTI
or a Notified Body?



-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: EN60950:2000 & EN60950-1 last dates of manufacture

[Peter L. Tarver]

All -

I have received a number of responses, for which I am
grateful.

As a matter of course, we must all try to act as lawyers in
pursuit of compliance.  To that end, I reviewed the
documents I had in hand [which included the CSA transition
document (which I treat as a third hand interpretation), the
LVD, the list of harmonized standards from the OJ, the Guide
to the Implementation of Directives Based on New Approach
and Global Approach, EN60950:1992 through A4 and a copy of
the Forward to EN60950:2000], prior to posting my query.
None of these provided me with a feeling of certain
knowledge.


As points of comparison, I offer the following citations.

>From Guide to the Implementation of Directives Based on New
Approach and Global Approach (the so-called "Blue Guide"):

“4.5. Revision of harmonised standards

“Following its internal regulations, the relevant European
standard organisation lays down the date of publication at
national level of the revised harmonised standard, and the
date of withdrawal of the old standard. The transitional
period is normally the time period between these two dates.
During this transitional period both harmonised standards
give presumption of conformity, provided that the conditions
for this are met. After this transitional period, only the
revised harmonised standard gives a presumption of
conformity.

“The Commission may consider that, for safety or other
reasons, the old version of the harmonised standard must
cease giving a presumption of conformity before its date of
withdrawal, set by European standards organisation in
question. In such cases, the Commission fixes an earlier
date after which the standard will no longer give a
presumption of conformity, and publishes this information in
the Official Journal. If circumstances allow, the Commission
consults the Member States prior to taking a decision to
reduce the period during which the standard gives a
presumption of conformity.

“The reference of the revised harmonised standard, the
reference of the old harmonised standard, and the date where
the presumption of conformity of the old standard finishes
are published together in the Official Journal.”

>From EN60950:1992, Forward to A4:

“For products which have complied with EN 60950:1992 and its
amendments A1:1993, A2:1993, A3:1995 before 1998-08-01, as
shown by the manufacturer or by a certification body, this
previous standard may continue to apply for production until
2003-08-01.”

You will note that there is a distinct difference in
language between the two documents.  EN60950:1992 is quite
clear, while the Blue Guide is not quite satisfying.

Other points of comparison lie in the last dates of
manufacture in the various forwards EN60950:1992 and the
right-most column from the OJ's list of harmonized standards
titled  "Date of cessation of presumption of conformity of
the superseded standard."  These dates agree completely,
though I still wished to eliminate all doubt, because of the
differences in language.  The language of the list of
harmonized standards and the Blue Guide don't explicitly
mention manufacturing and could be interpreted as the last
date a product certification could be obtained using a
standard, which is consistent with the text of the forwards
to EN60950:1992.

With the absence of similar verbiage in the forward to
EN60950:2000 and knowing that the last dates of manufacture
in EN60950:1992 occurred some time after the DOW for each
amendment, I am left desirous of certainty.  With the advent
of an additional interpretation (I say interpretation,
because I've seen nothing explicit, official and in writing
to support this) that the DOW is the last date a product may
be offered for sale, irrespective of dates of manufacturing,
what used to apply for last dates of manufacture, and that
product might be in a distribution path well prior to the
DOW, but not yet sold.

Not to disparage the value of previous postings or to doubt
the veracity of posters on the subject, but we all must take
posts to the list server with a grain of cynicism, lest we
find ourselves paddleless up a reeking creek, heading for
the rapids.  The old saw about "assume" plays a key role.

I now wish to change my query, to alleviate the irritation
some may have felt at this being "asked again": is there an
official document available that provides unambiguous
clarity defining "date of cessation of presumption of
conformity of the superseded standard," in the context of
manufacturing?  My searches on Europa, UK DTI and the
internet in general have not to date yielded useful results.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com


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Re: EN60950:2000 & EN60950-1 last dates of manufacture

[John Woodgate]

I read in !emc-pstc that Peter L. Tarver 
wrote (in )
about 'EN60950:2000 & EN60950-1 last dates of manufacture' on Fri, 1 Nov
2002:
>
>A poser for those in the know.
>
>In EN60950:1992 and its subsequent amendments, the Forward
>contained three dates:
>
>   1) DOP - a date of publication when each EU nation was
>required to implement the new version of the standard
>
>   2) DOW - the last date by which previous national versions
>(called "conflicting") of the standard had to be withdrawn
>by each EU nation
>
>   3) the last date for which a product evaluated to a
>previous version of the standard could be manufactured,
>provided its certifications were issued before the DOW (was
>typically 3-5 years)
>
>In looking at the Forward to EN60950:2000, the third date is
>conspicuously absent.   I don't have a copy of
>EN60950-1:2001, but I suspect the same is true.
>
>I made two queries this afternoon to separate NCBs.  Neither
>could not point to any such specific date, but both believed
>that third date might be the same as the DOW.  I've asked
>both for a more definitive answer by providing something in
>writing that unambiguously substantiates their claims.

I've posted here about that several times. The dow IS the last date at
which products conforming to the old standard may be **offered for sale
by the manufacturer**, not *manufactured*. Products in the distribution
chain are tolerated for about one year after the dow.

The dow is normally the same as the 'date of cessation of presumption of
compliance of the superseded standard' (docopocoss), although the latter
is set by the Commission and could be different from the dow.
>
>I also want to check through the knowledge base of this
>august collection of crania, in case the others fall short
>of my expectations.
>
>Does anyone on the list have anything in writing (hearsay is
>of no help) regarding the last date of manufacture for
>products compliant with EN60950:1992+A1+A2+A3+A4+A11?  Same
>for EN60950:2000?  If so, I would appreciate a copy of this
>(these) document(s).
>
>
The information is in the standards themselves; you need no other
document. But it makes your brain hurt to try to decipher what the
various dates of the multiple amendments actually mean. The information
(of the actual docopocosses) is also in the lists of 'notified
standards' available from the Commission web site.

The dow for EN60950:1992 and amendments is the dow given in the 2000
edition. The dow for the 2000 edition is the one given in EN60950-1.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: EN60950-1 Sect 2.5 Limited Power sources PTC's

[Gregg Kervill]

For the record - I was doing a Single Fault analysis on a product that used
a PTC and a relay to prevent welding switch contacts. (No it was not my
idea - because...) when I got the engineer to simulate a s/c PSU the PTC
exploded - sent burning material out through (compliant) ventilation slots
onto the carpet which started to smolder.

The worst part of this story was yet to come when we discovered that the PTC
have MODIFIED the di/dt of the fault current and destroyed discrimination
between the thermal and electromechanical over-current devices up-stream.  I
cannot go into too much detail as it might reveal the name of the client -
suffice it to say that the result could have been the biggest oil slick that
the world has seen.

That is why Product Safety engineering is so interesting.

Best regards

Gregg


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Re: EN60950-1 Sect 2.5 Limited Power sources

[Rich Nute]

Hi Tom:


>   Is it permitted to use PTC as an overcurrent protective device
>   for power sources not inherently limited?
>   I don't have EN60950-1 here, but I remember it must be a fuse
>   or other non-autoreset device.

I said:

"The trick is to determine if your test houses can 
 class the PTC as an 'overcurrent protective device.'"

Another subscriber said that the PTC is a resistor and
therefore a PTC-protected LPS must be "inherently" limited.

I suggested the PTC as an overcurrent protective device
because as its resistance goes up, the PTC provides
protection against overcurrent.  


Best regards,
Rich





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Re: EN60950-1 Sect 2.5 Limited Power sources

[T.Sato]

On Tue, 3 Sep 2002 15:49:43 -0700 (PDT),
  Rich Nute  wrote:

> If you use a PTC, then your output need not necessarily be 
> considered "inherently limited."  In this case, your 
> maximum output current is 100 amps and your maximum VA is 
> 250, i.e., 25 amps (with the PTC shorted).  The trick is 
> to determine if your test houses can class the PTC as an 
> "overcurrent protective device."  

Is it permitted to use PTC as an overcurrent protective device
for power sources not inherently limited?
I don't have EN60950-1 here, but I remember it must be a fuse
or other non-autoreset device.

Regards,
Tom

--
Tomonori Sato  
URL: http://member.nifty.ne.jp/tsato/

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Re: EN60950-1 Sect 2.5 Limited Power sources

[Rich Nute]

Hi Alex:


>   We use a linear (basically a transformer with a PTC thermistor) class II
>   SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs tested
>   the O/P Isc with a direct application of the sc. The other lab tested the
>   O/P Isc by applying a load of 8A. The results were therefore interpreted
>   differently.

>   1.  What is the correct method to test for a Limited Power source in
>   determining what enclosure is required?

Limited Power Source is a combination of a number
of criteria:

output voltage;
output current;
output volt-amperes.

These are independent criteria.

Note that Isc is defined as:

"Maximum output current after 60 s of operation with 
 any non-capacitive load, including short-circuit."

Both labs are wrong.

If a power supply shuts down due to a short-circuit, then
it is necessary to determine the maximum current where the
power supply does not shut down.  Typically, this is about
twice rated output.  Since your power supply is rated 5 A,
then I would expect the overpower to take effect at about
10 A output.

When testing a power supply output for LPS, start at rated
load and gradually increase the load.  If the output 
exceeds 8 amps or any other criteria, then the output is
not LPS.

Then, introduce the single, worst-case fault in the
regulating circuit, and repeat the test.  In your case,
this means shorting the PTC, in which case the output will
certainly exceed 8 amperes.

By the way, your output also fails the output volt-amperes
criteria.  If the open-circuit output voltage is 10 volts, 
then the maximum VA is 50, or 5 amps.  

Since one lab only did the output short-circuit test, the
results are not correct.

Since the other lab did a single test at 8 amps, this is
more-or-less okay, but for the wrong reasons. 

Neither lab did the VA test!  The VA test would have proved 
the unit failed at 5 A output.

Neither lab introduced a fault in the regulating network!
(But, the didn't need to since the unit failed under normal
operating conditions.)

Both labs are wrong, but one came up with the correct
determination.  (Of course ONE had to be correct!)  :-)

If you use a PTC, then your output need not necessarily be 
considered "inherently limited."  In this case, your 
maximum output current is 100 amps and your maximum VA is 
250, i.e., 25 amps (with the PTC shorted).  The trick is 
to determine if your test houses can class the PTC as an 
"overcurrent protective device."  

A colleague claims that very few test houses really know
how to do LPS testing.  I concur, and your report confirms
this again.


Best regards,
Rich







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RE: EN60950-1 Sect 2.5 Limited Power sources

[Robert Johnson]

1.  What is the correct method to test for a Limited Power source in
determining what enclosure is required?
The Isc limits must be met regardless of the load, 
not only at 30a or 8a. You need to do sufficient 
testing to satisfy yourself it will comply in general. 
In this case you have demonstrated a failure.

2.  If a fire enclosure was needed what is the minimum plastic
rating
i.e. 94V0, V1 or what?
94V-0 is not mentioned in the standard. 
Requirements would be for 5-V, V-1 or 
other requirements in clause 4.7.3.2 
if a fire enclosure is required.
3.  I cannot put a 5A fuse in the product, the lab says that the
overcurrent protective device must be outwith the non-fire enclosure in
order to stop the non compliant energy source entering the enclosure. Is
this correct?
Somewhat. The portion of the circuit not meeting the 
requirement is the part which needs the enclosure. 
Note that this does not mean the entire product. 
You can provide a fire enclosure around a small entry 
area and not include the rest of the product.
4.  Similarly, I cannot use a resettable fuse in the product to meet
these requirements?
You may meet the requirements with fuse, PTC or other limiter.
5.  Does the PTC used in the power supply need to meet the IEC
60730-1?
Not if you can assure the requirements relevant to the 
application are met by your own testing. See clause 1.5.2.

Bob Johnson
ITE Safety
 

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org] On Behalf Of Alex McNeil
Sent: Friday, August 30, 2002 5:25 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: EN60950-1 Sect 2.5 Limited Power sources


Hi group,

I have a query on the understanding of the above section. I thought I
fully
understood it until I used a different lab for Product Safety Compliance
testing (both accredited!).

We use a linear (basically a transformer with a PTC thermistor) class II
SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs
tested
the O/P Isc with a direct application of the sc. The other lab tested
the
O/P Isc by applying a load of 8A. The results were therefore interpreted
differently.

Isc (direct) = 30A falling to 0A within 30secs. Considered a PASS (8A
for <
1min)
Isc (8A load) = 8A for > 2mins. Considered a FAIL (8A > 1min)

This has a crucial bearing on whether I need a fire enclosure or not for
my
all plastic enclosure!

1.  What is the correct method to test for a Limited Power source in
determining what enclosure is required?
2.  If a fire enclosure was needed what is the minimum plastic
rating
i.e. 94V0, V1 or what?
3.  I cannot put a 5A fuse in the product, the lab says that the
overcurrent protective device must be outwith the non-fire enclosure in
order to stop the non compliant energy source entering the enclosure. Is
this correct?
4.  Similarly, I cannot use a resettable fuse in the product to meet
these requirements?
5.  Does the PTC used in the power supply need to meet the IEC
60730-1?

I would very much appreciate clarification on this matter.

THANKS!!

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com


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<>

RE: EN60950-1 Sect 2.5 Limited Power sources

[Peter Merguerian]

Alex,

1.  What is the correct method to test for a Limited Power source in
determining what enclosure is required?

Peter: The correct method for inherently limited power source is to measure
the output current (Isc) after 60 seconds of operation with the load
adjusted to maintain the Isc current limit (8.0 A). In your case the PTC
serves as the impedance limiting the current flow. I do not understand why
the Isc (8A load) lab failed you since you did not exceed the 8A and the
result should have been acceptable.

2.  If a fire enclosure was needed what is the minimum plastic rating
i.e. 94V0, V1 or what?

Peter:  Sounds like you have a movable equipment with a total mass < 18 kg.
For a fire enclosure, you need a 94V-1 enclosure or one that can withstsnd
the tests of Clause A.2 

3.  I cannot put a 5A fuse in the product, the lab says that the
overcurrent protective device must be outwith the non-fire enclosure in
order to stop the non compliant energy source entering the enclosure. Is
this correct?

Peter: I assume you mean you cannot put a  max. 5 A or less to meet the Isc
of less than or = 1000/Uoc for power sources not inherently limited. The
rated current values of the overcurrent protector in Table 9 are for devices
located in the secondary.  If the fuse is located in the primary, the max
values of Table 9 should be adjusted based on the pri/sec windings turns
ratio.  For example, if a transformer has a 5:1 turns ratio, then the  max
values of the rated currents for the overcurrent devices in the primary
should be  adjusted to 1/5 of the values shown, or in your case 1/5 (5 A) =
1 A

The fuse and transformer must be within the fire enclosure. You can get away
with it if your fuse is within an appliance inlet in the primary, your leads
are PVC, TFE, PTFE, FEP or neoprene and the transformer itself (except
laminations) has its own fire enclosure. There are many transformer
constructions with bobbin/cover constructions which would meet the fire
enclosure requirements.

For reference, see 4.7.2.1 (parts requiring fire enclosures) and 4.7.2.2
(parts not requiring fire enclosures).

4.  Similarly, I cannot use a resettable fuse in the product to meet
these requirements?

Peter: You have a PTC within the transformer; make sure it is approved and
meets the tests in IEC 60730-1, clauses 15, 17, J15 and J17.

5.  Does the PTC used in the power supply need to meet the IEC 60730-1?

Peter: Only the parts specified above.


Summary: It seems you wish to use a cheap enclosure material (94HB). Get a
fused applied inlet. Install a fuse value based on the transformer pri/sec
turns ratio as mentioned above. Use a transformer with a 94V-1 fire
enclosure over the windings and make sure its' wires are PVC, TFE, PTFE, FEP
or neoprene. With the fuse bypassed, make sure you meet the limit for Isc
(A) and S (VA) in Table 9 in the standard. You are all set and ready.

 
This e-mail message may contain privileged or confidential information. If
you are not the intended recipient, you may not disclose, use, disseminate,
distribute, copy or rely upon this message or attachment in any way. If you
received this e-mail message in error, please return by forwarding the
message and its attachments to the sender.






PETER S. MERGUERIAN
Technical Director
I.T.L. (Product Testing) Ltd.
26 Hacharoshet St., POB 211
Or Yehuda 60251, Israel
Tel: + 972-(0)3-5339022  Fax: + 972-(0)3-5339019
Mobile: + 972-(0)54-838175
http://www.itl.co.il
http://www.i-spec.com





-Original Message-
From: Alex McNeil [mailto:alex.mcn...@ingenicofortronic.com]
Sent: Friday, August 30, 2002 11:25 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: EN60950-1 Sect 2.5 Limited Power sources



Hi group,

I have a query on the understanding of the above section. I thought I fully
understood it until I used a different lab for Product Safety Compliance
testing (both accredited!).

We use a linear (basically a transformer with a PTC thermistor) class II
SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs tested
the O/P Isc with a direct application of the sc. The other lab tested the
O/P Isc by applying a load of 8A. The results were therefore interpreted
differently.

Isc (direct) = 30A falling to 0A within 30secs. Considered a PASS (8A  for <
1min)
Isc (8A load) = 8A for > 2mins. Considered a FAIL (8A > 1min)

This has a crucial bearing on whether I need a fire enclosure or not for my
all plastic enclosure!

1.  What is the correct method to test for a Limited Power source in
determining what enclosure is required?
2.  If a fire enclosure was needed what is the minimum plastic rating
i.e. 94V0, V1 or what?
3.  I cannot put a 5A fuse in the product, the lab says that the
overcurrent protective device must be outwith the non-fire enclosure in
order to stop the non compliant energy source entering the enclosure. Is
this correct?
4.  Similarly, I cannot use a resettable fuse in the product to meet
these requireme

RE: EN60950 3rd vs EN60950-1

[Kevin Richardson]

Yes.

Best regards,
Kevin Richardson

Stanimore Pty Limited
Compliance Advice & Solutions for Technology (including Australian Agent
Services)
(Legislation/Regulations/Standards)
Ph:   02-4329-4070   (Int'l: +61-2-4329-4070)
Fax:  02-4328-5639   (Int'l: +61-2-4328-5639)
Mobile:  04-1224-1620   (Int'l: +61-4-1224-1620)
Email:kevin.richard...@ieee.org

The material transmitted in this message and contained in any attachments to
this message is confidential and/or privileged information and is intended
only for the addressee/s. Any unauthorised use of or reliance upon this
material by persons or entities other than the addressee/s is prohibited. If
you receive this information in error, please notify the sender and destroy
any copies of the material immediately.



-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of
richwo...@tycoint.com
Sent: Tuesday, 16 July 2002 9:43 PM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



OK, let me ask the question again. Is EN60950-1 complete enought to evaluate
most ITE without the need of the subparts?

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: Brian McAuliffe [mailto:i...@mcac.ie]
Sent: Tuesday, July 16, 2002 2:35 AM
To: Ron Pickard; richwo...@tycoint.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1


I would agree, kind of like IEC/EN 60335 for domestic electrical and similar
equipment.

Brian McAuliffe
MCA Compliance Solutions
www.mcac.ie

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ron Pickard
Sent: 15 July 2002 21:28
To: richwo...@tycoint.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1




Richard et al,

It is my understanding that IEC/EN/?? 60950-1 is intended to supercede
IEC/EN/?? 60950 3rd Edition.
This is evidenced by the statement from CENELEC's web site relating to
EN60950-1, which is
"Supersedes EN 60950:2000". The IEC's website provides this statement "This
first edition of IEC
60950-1 cancels and replaces the third edition of IEC 60950, issued in 1999,
and constitutes a
technical revision".

For specific requirements for particular product variants, other sub-parts
(EN60950-xx) would be
necessary. BTW, EN60950-21 (remote power feeding) is the only sub-part on
record with CENELEC
according to their website. In addition to Part 21, the IEC's website also
describes "Part 22:
Equipment installed outdoors" and "Part 23: Large IT equipment with integral
robotics".

So, I believe that if products do not apply to any sub-part, then I would
presume that sub-part 1
would be the only sub-part that would apply.

Comments?

Best regards,

Ron Pickard
rpick...@hypercom.com





  richwo...@tycoint.com
  Sent by:  To:
emc-p...@majordomo.ieee.org
  owner-emc-pstc@majordo    cc:
  mo.ieee.org   Subject:  RE: EN60950
3rd vs EN60950-1


  07/15/02 11:45 AM
  Please respond to
  richwoods







A couple of months ago, I asked the group if I should be using EN60650-1.
The answer was "no", until and unless the particular part was published that
covered my product. In other words, the new edition is incomplete and
subsequent parts will need to be published before it can be used instead of
the current edition.

Richard Woods
Sensormatic Electronics
Tyco International




-Original Message-
From: Brian O'Connell [mailto:boconn...@t-yuden.com]
Sent: Monday, July 15, 2002 9:25 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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RE: EN60950 3rd vs EN60950-1

[richwoods]

OK, let me ask the question again. Is EN60950-1 complete enought to evaluate
most ITE without the need of the subparts?

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: Brian McAuliffe [mailto:i...@mcac.ie]
Sent: Tuesday, July 16, 2002 2:35 AM
To: Ron Pickard; richwo...@tycoint.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1


I would agree, kind of like IEC/EN 60335 for domestic electrical and similar
equipment.

Brian McAuliffe
MCA Compliance Solutions
www.mcac.ie

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ron Pickard
Sent: 15 July 2002 21:28
To: richwo...@tycoint.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1




Richard et al,

It is my understanding that IEC/EN/?? 60950-1 is intended to supercede
IEC/EN/?? 60950 3rd Edition.
This is evidenced by the statement from CENELEC's web site relating to
EN60950-1, which is
"Supersedes EN 60950:2000". The IEC's website provides this statement "This
first edition of IEC
60950-1 cancels and replaces the third edition of IEC 60950, issued in 1999,
and constitutes a
technical revision".

For specific requirements for particular product variants, other sub-parts
(EN60950-xx) would be
necessary. BTW, EN60950-21 (remote power feeding) is the only sub-part on
record with CENELEC
according to their website. In addition to Part 21, the IEC's website also
describes "Part 22:
Equipment installed outdoors" and "Part 23: Large IT equipment with integral
robotics".

So, I believe that if products do not apply to any sub-part, then I would
presume that sub-part 1
would be the only sub-part that would apply.

Comments?

Best regards,

Ron Pickard
rpick...@hypercom.com





  richwo...@tycoint.com
  Sent by:  To:
emc-p...@majordomo.ieee.org
  owner-emc-pstc@majordocc:
          mo.ieee.org   Subject:  RE: EN60950
3rd vs EN60950-1


  07/15/02 11:45 AM
  Please respond to
  richwoods







A couple of months ago, I asked the group if I should be using EN60650-1.
The answer was "no", until and unless the particular part was published that
covered my product. In other words, the new edition is incomplete and
subsequent parts will need to be published before it can be used instead of
the current edition.

Richard Woods
Sensormatic Electronics
Tyco International




-Original Message-
From: Brian O'Connell [mailto:boconn...@t-yuden.com]
Sent: Monday, July 15, 2002 9:25 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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All emc-pstc postings are archiv

RE: EN60950 3rd vs EN60950-1

[Kevin Richardson]

Ron,

As I understand it, Part 1 (IEC 60950-1) is indeed a complete and
stand-alone replacement for IEC 60950 3rd Edition.  Future parts such as
60950-21, -22 & -23 will be addressing specific product types or product
environments etc.  IEC 60950-1 is however generic and as such a product
falling within the scope of any future parts will still be expected to meet
the requirements of 60950-1 where applicable (i.e. any parts other than Part
1 will be complimentary and in addition to the requirements of Part 1 for
that type of equipment).


Best regards,
Kevin Richardson

Stanimore Pty Limited
Compliance Advice & Solutions for Technology (including Australian Agent
Services)
(Legislation/Regulations/Standards)
Ph:   02-4329-4070   (Int'l: +61-2-4329-4070)
Fax:  02-4328-5639   (Int'l: +61-2-4328-5639)
Mobile:  04-1224-1620   (Int'l: +61-4-1224-1620)
Email:kevin.richard...@ieee.org

The material transmitted in this message and contained in any attachments to
this message is confidential and/or privileged information and is intended
only for the addressee/s. Any unauthorised use of or reliance upon this
material by persons or entities other than the addressee/s is prohibited. If
you receive this information in error, please notify the sender and destroy
any copies of the material immediately.



-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ron Pickard
Sent: Tuesday, 16 July 2002 6:28 AM
To: richwo...@tycoint.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1




Richard et al,

It is my understanding that IEC/EN/?? 60950-1 is intended to supercede
IEC/EN/?? 60950 3rd Edition.
This is evidenced by the statement from CENELEC's web site relating to
EN60950-1, which is
"Supersedes EN 60950:2000". The IEC's website provides this statement "This
first edition of IEC
60950-1 cancels and replaces the third edition of IEC 60950, issued in 1999,
and constitutes a
technical revision".

For specific requirements for particular product variants, other sub-parts
(EN60950-xx) would be
necessary. BTW, EN60950-21 (remote power feeding) is the only sub-part on
record with CENELEC
according to their website. In addition to Part 21, the IEC's website also
describes "Part 22:
Equipment installed outdoors" and "Part 23: Large IT equipment with integral
robotics".

So, I believe that if products do not apply to any sub-part, then I would
presume that sub-part 1
would be the only sub-part that would apply.

Comments?

Best regards,

Ron Pickard
rpick...@hypercom.com





  richwo...@tycoint.com
  Sent by:  To:
emc-p...@majordomo.ieee.org
  owner-emc-pstc@majordo    cc:
  mo.ieee.org   Subject:  RE: EN60950
3rd vs EN60950-1


  07/15/02 11:45 AM
  Please respond to
  richwoods







A couple of months ago, I asked the group if I should be using EN60650-1.
The answer was "no", until and unless the particular part was published that
covered my product. In other words, the new edition is incomplete and
subsequent parts will need to be published before it can be used instead of
the current edition.

Richard Woods
Sensormatic Electronics
Tyco International




-Original Message-
From: Brian O'Connell [mailto:boconn...@t-yuden.com]
Sent: Monday, July 15, 2002 9:25 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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 Jim Bacher:  

RE: EN60950 3rd vs EN60950-1

[Brian McAuliffe]

The draft EN60950-1 that I have (prEN60950-1 prAA July 2001) has a DOP of
'IEC 60950-1 publication date + 9 months', and, a DOW of 'July 1 2006'. So
there is some time before you must adopt the EN60950-1 standard for new
product released.

It also gives a justification for why this DOW has been chosen.

Brian McAuliffe
MCA Compliance Solutions
www.mcac.ie



-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Brian O'Connell
Sent: 15 July 2002 14:25
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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RE: EN60950 3rd vs EN60950-1

[Brian McAuliffe]

I would agree, kind of like IEC/EN 60335 for domestic electrical and similar
equipment.

Brian McAuliffe
MCA Compliance Solutions
www.mcac.ie

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Ron Pickard
Sent: 15 July 2002 21:28
To: richwo...@tycoint.com
Cc: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1




Richard et al,

It is my understanding that IEC/EN/?? 60950-1 is intended to supercede
IEC/EN/?? 60950 3rd Edition.
This is evidenced by the statement from CENELEC's web site relating to
EN60950-1, which is
"Supersedes EN 60950:2000". The IEC's website provides this statement "This
first edition of IEC
60950-1 cancels and replaces the third edition of IEC 60950, issued in 1999,
and constitutes a
technical revision".

For specific requirements for particular product variants, other sub-parts
(EN60950-xx) would be
necessary. BTW, EN60950-21 (remote power feeding) is the only sub-part on
record with CENELEC
according to their website. In addition to Part 21, the IEC's website also
describes "Part 22:
Equipment installed outdoors" and "Part 23: Large IT equipment with integral
robotics".

So, I believe that if products do not apply to any sub-part, then I would
presume that sub-part 1
would be the only sub-part that would apply.

Comments?

Best regards,

Ron Pickard
rpick...@hypercom.com





  richwo...@tycoint.com
  Sent by:  To:
emc-p...@majordomo.ieee.org
  owner-emc-pstc@majordocc:
          mo.ieee.org   Subject:  RE: EN60950
3rd vs EN60950-1


  07/15/02 11:45 AM
  Please respond to
  richwoods







A couple of months ago, I asked the group if I should be using EN60650-1.
The answer was "no", until and unless the particular part was published that
covered my product. In other words, the new edition is incomplete and
subsequent parts will need to be published before it can be used instead of
the current edition.

Richard Woods
Sensormatic Electronics
Tyco International




-Original Message-
From: Brian O'Connell [mailto:boconn...@t-yuden.com]
Sent: Monday, July 15, 2002 9:25 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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 Jim Bacher: j.bac...@ieee.org

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To cancel your subscription

RE: EN60950 3rd vs EN60950-1

[Ron Pickard]

Richard et al,

It is my understanding that IEC/EN/?? 60950-1 is intended to supercede 
IEC/EN/?? 60950 3rd Edition.
This is evidenced by the statement from CENELEC's web site relating to 
EN60950-1, which is
"Supersedes EN 60950:2000". The IEC's website provides this statement "This 
first edition of IEC
60950-1 cancels and replaces the third edition of IEC 60950, issued in 1999, 
and constitutes a
technical revision".

For specific requirements for particular product variants, other sub-parts 
(EN60950-xx) would be
necessary. BTW, EN60950-21 (remote power feeding) is the only sub-part on 
record with CENELEC
according to their website. In addition to Part 21, the IEC's website also 
describes "Part 22:
Equipment installed outdoors" and "Part 23: Large IT equipment with integral 
robotics".

So, I believe that if products do not apply to any sub-part, then I would 
presume that sub-part 1
would be the only sub-part that would apply.

Comments?

Best regards,

Ron Pickard
rpick...@hypercom.com





  
  richwo...@tycoint.com 
  
  Sent by:  To:   
emc-p...@majordomo.ieee.org 
  owner-emc-pstc@majordocc: 
  
          mo.ieee.org   Subject:  RE: EN60950 3rd 
vs EN60950-1

  

  
  07/15/02 11:45 AM 
  
  Please respond to 
  
  richwoods 
  

  

  





A couple of months ago, I asked the group if I should be using EN60650-1.
The answer was "no", until and unless the particular part was published that
covered my product. In other words, the new edition is incomplete and
subsequent parts will need to be published before it can be used instead of
the current edition.

Richard Woods
Sensormatic Electronics
Tyco International




-Original Message-
From: Brian O'Connell [mailto:boconn...@t-yuden.com]
Sent: Monday, July 15, 2002 9:25 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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 Dave Heald:   davehe...@attbi.com

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 Richard Nute:   ri...@ieee.org
 Jim Bacher: j.bac...@ieee.org

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Click on "browse" and then "emc-pstc mailing list"

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RE: EN60950 3rd vs EN60950-1

[richwoods]

A couple of months ago, I asked the group if I should be using EN60650-1.
The answer was "no", until and unless the particular part was published that
covered my product. In other words, the new edition is incomplete and
subsequent parts will need to be published before it can be used instead of
the current edition.

Richard Woods
Sensormatic Electronics
Tyco International




-Original Message-
From: Brian O'Connell [mailto:boconn...@t-yuden.com]
Sent: Monday, July 15, 2002 9:25 AM
To: emc-p...@majordomo.ieee.org
Subject: RE: EN60950 3rd vs EN60950-1



In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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 Jim Bacher: j.bac...@ieee.org

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Click on "browse" and then "emc-pstc mailing list"

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RE: EN60950 3rd vs EN60950-1

[Brian O'Connell]

In my copy of EN 60950-1:2002, purchased from BSI, the DoP is listed as
December 01, 2002.

R/S,
Brian O'Connell
Taiyo Yuden (USA), Inc.


-Original Message-
From: Ron Pickard [mailto:rpick...@hypercom.com]
Sent: Friday, July 12, 2002 3:10 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 3rd vs EN60950-1

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com

---
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Re: EN60950 3rd vs EN60950-1

[Ron Pickard]

Hi Allen,

Thanks for your reply, however, I highly doubt that these products will be 
obsoleted by then, which
is the source of my concern and my query.

Also, at some standards purchasing houses, I've noticed that EN60950 3rd 
Edition has been, or is
being, superceded by EN60950-1. This has caused me to ask the question of OJ 
publication.

Best regards,

Ron Pickard
rpick...@hypercom.com




 
  akemevor@netzero. 
 
  net  To:   rpick...@hypercom.com  
 
   cc:   
emc-p...@majordomo.ieee.org 
  07/12/02 01:37 PMSubject:  Re: EN60950 3rd vs 
EN60950-1

 

 




Ron,
There is usually a few years transition followed by a a few more years grand 
fathering period when a
new
standard introduced. Your product may be obsolete by then.
Allen

Ron Pickard wrote:

> To all,
>
> I am trying to decide, not if, but to which of the above standards must be 
> complied with on a
> logistics basis.
>
> Does anyone have any knowledge as to when EN60950-1 harmonization will get 
> published in the OJ?
When
> is it expected? I know that EN60950-1 is not yet officially harmonized under 
> the LVD yet, but
> EN69050 3rd Edition is.
>
> I do not want to go through the time and expense (not insignificant) to 
> acquire CB certs/reports
to
> IEC/EN60950 3rd to only find out that I have to go through it all over again 
> for conformance to
> IEC/EN60950-1 shortly thereafter. Management will not find it palatable going 
> through this twice
> when only once would have sufficed.
>
> However, I will do what I have to do, but it will be nice to have a bit of 
> guidance here. And, I'm
> sure that I'm not the only one in this predicament.
>
> Any replies would certainly be appreciated.
>
> Best regards,
>
> Ron Pickard
> rpick...@hypercom.com
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
>
> To cancel your subscription, send mail to:
>  majord...@ieee.org
> with the single line:
>  unsubscribe emc-pstc
>
> For help, send mail to the list administrators:
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>  Dave Heald:   davehe...@attbi.com
>
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>  Jim Bacher: j.bac...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
> http://ieeepstc.mindcruiser.com/
> Click on "browse" and then "emc-pstc mailing list"






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Re: EN60950 3rd vs EN60950-1

[Allen Kemevor]

Ron,
There is usually a few years transition followed by a a few more years grand 
fathering period when a new
standard introduced. Your product may be obsolete by then.
Allen

Ron Pickard wrote:

> To all,
>
> I am trying to decide, not if, but to which of the above standards must be 
> complied with on a
> logistics basis.
>
> Does anyone have any knowledge as to when EN60950-1 harmonization will get 
> published in the OJ? When
> is it expected? I know that EN60950-1 is not yet officially harmonized under 
> the LVD yet, but
> EN69050 3rd Edition is.
>
> I do not want to go through the time and expense (not insignificant) to 
> acquire CB certs/reports to
> IEC/EN60950 3rd to only find out that I have to go through it all over again 
> for conformance to
> IEC/EN60950-1 shortly thereafter. Management will not find it palatable going 
> through this twice
> when only once would have sufficed.
>
> However, I will do what I have to do, but it will be nice to have a bit of 
> guidance here. And, I'm
> sure that I'm not the only one in this predicament.
>
> Any replies would certainly be appreciated.
>
> Best regards,
>
> Ron Pickard
> rpick...@hypercom.com
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
>
> To cancel your subscription, send mail to:
>  majord...@ieee.org
> with the single line:
>  unsubscribe emc-pstc
>
> For help, send mail to the list administrators:
>  Ron Pickard:  emc-p...@hypercom.com
>  Dave Heald:   davehe...@attbi.com
>
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>  Richard Nute:   ri...@ieee.org
>  Jim Bacher: j.bac...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
> http://ieeepstc.mindcruiser.com/
> Click on "browse" and then "emc-pstc mailing list"
<>

RE: EN60950 3rd vs EN60950-1

[Peter Tarver]

Ron -

I do not have a view on publication of EN60950-1 in the OJ,
but the IEC Web Store indicates a Technical Report Form was
created in APR2002 and is available.


Regards,

Peter L. Tarver, PE
Product Safety Manager
Sanmina-SCI Homologation Services
San Jose, CA
peter.tar...@sanmina-sci.com

> -Original Message-
> From: Ron Pickard
> Sent: Friday, July 12, 2002 9:30 AM
>
> To all,
>
> I am trying to decide, not if, but to which of
> the above standards must be complied with on a
> logistics basis.
>
> Does anyone have any knowledge as to when
> EN60950-1 harmonization will get published in the OJ? When
> is it expected? I know that EN60950-1 is not yet
> officially harmonized under the LVD yet, but
> EN69050 3rd Edition is.
>
> I do not want to go through the time and expense
> (not insignificant) to acquire CB certs/reports to
> IEC/EN60950 3rd to only find out that I have to
> go through it all over again for conformance to
> IEC/EN60950-1 shortly thereafter. Management will
> not find it palatable going through this twice
> when only once would have sufficed.
>
> Best regards,
>
> Ron Pickard
> rpick...@hypercom.com


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RE: EN60950 functional earthing.

[Gert Gremmen]

It is definitely not a requirement for EMC, regardless of the standard.
The ground connection has no function in EMC but for the extremely low
frequencies.

I believe that is a generic design principle to ALWAYS connect
protective ground first and disconnect last when connecting any connector
regardless the requirements of the standard. Even when using fixed
connections make a habit of placing the ground connector in such a place
that when pulling of the wires by force, the ground wire is pulled out last.
(many connectors for fixed wiring do have such a topology by default)
If that is impossible, wiring practice normally prescribe that the
ground wire be cut off slightly (0.5") longer then phase and return
wires of the cable, ensuring the proper disconnect order of the wires
even if forced.

A peoduct safety designer should  not inquire if any
design rule is mandatory in a specific standard, but instead,
question himself if any extra safety measure can be included in
the design without exceeding the design specifications (might include
cost!).

The PE connect first disconnect last principle is so fundamental to safety,
that it should be honored in any design, even not mains related.

The ground connection is one of the 2 fundamental safety layers between
user/operator and parts at live voltage. As important as insulation. Would
you
ask the same question if it concerned internal wire insulation ?

The actual moment of connecting/disconnecting power plugs is precisely the
same moment
where users put one hand on the equipments cover and push-in/pull-out the
plug
with the other hand. At that same moment emc filter capacitors charge with a
high
peak current steered by a possible steep voltage (up to 320 Volts in
europe).
Equipment needs grounding most at exactly *that* moment.

Regards

Gert Gremmen
ce-test




-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Lou Aiken
Sent: maandag 1 juli 2002 17:27
To: Jon Jones; Emc-Pstc (E-mail)
Subject: Re: EN60950 functional earthing.



My recollection is (without reading the standard) that the make first /
break last requirement only applies to connectors operated by the user or
other non trained persons.

Then it should also seem reasonable that the requirement would not apply to
a product meeting ALL class II requirements.

However, protection preventing contact (by the test finger) with a live pin
of a partially inserted plug or connector WILL apply if the connector can be
used by non trained persons, regardless of the protection class.Rgds,

Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

Tel  251 981 6786
Fax 251 981 3054
Mobile 251 979 4648
- Original Message -
From: Jon Jones 
To: Emc-Pstc (E-mail) 
Sent: Monday, July 01, 2002 11:40 AM
Subject: EN60950 functional earthing.


>
> Group,
>
> Regarding Functional earthing requirements for Class II equipment.
>
> Is there a general requirement for the functional earth in an equipments
> power connector to follow the make first break last rule with regards to
EMC
> (EN55022) and Safety.
>
> Thanks in advance
>
>
> Jon Jones
> ATL telecom.
>
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
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---
This message is from

Re: EN60950 functional earthing.

[Lou Aiken]

My recollection is (without reading the standard) that the make first /
break last requirement only applies to connectors operated by the user or
other non trained persons.

Then it should also seem reasonable that the requirement would not apply to
a product meeting ALL class II requirements.

However, protection preventing contact (by the test finger) with a live pin
of a partially inserted plug or connector WILL apply if the connector can be
used by non trained persons, regardless of the protection class.Rgds,

Lou Aiken, LaMer LLC
27109 Palmetto Drive
Orange Beach, AL
36561 USA

Tel  251 981 6786
Fax 251 981 3054
Mobile 251 979 4648
- Original Message -
From: Jon Jones 
To: Emc-Pstc (E-mail) 
Sent: Monday, July 01, 2002 11:40 AM
Subject: EN60950 functional earthing.


>
> Group,
>
> Regarding Functional earthing requirements for Class II equipment.
>
> Is there a general requirement for the functional earth in an equipments
> power connector to follow the make first break last rule with regards to
EMC
> (EN55022) and Safety.
>
> Thanks in advance
>
>
> Jon Jones
> ATL telecom.
>
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
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>  Jim Bacher: j.bac...@ieee.org
>
> All emc-pstc postings are archived and searchable on the web at:
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RE: EN60950:1992 vs EN60950:2000

[richwoods]

I found the following areas of change that affects our equipment (no TNV).
Other sections may have also changed.

1.3.6: equipment orientation clarified
1.5.6: requirements for X1 an X2 caps has changed and Y cap standard added
1.7.1: location of power rating marking revised
2.4.2: limited current circuit capacitance value depends upon voltage
Table 2G (pg 83): examples of insulation applications expanded and clarified
2.10.3.1: Annex G provides alternate method for determining clearances
4.2.10: wall and ceiling mounted equipment load test
4.3.8: batteries
4.6.4: openings in transportable equipment
4.7.1: the two methods of reducing risk of fire is clarified - method 2 now
says a fire enclosure is not required
4.7.2: cond
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RE: EN60950:1992 vs EN60950:2000

[Alex McNeil]

Hi Duncan,

I have the following information, I think I got it from my local KTL lab:

EN60950:1992 VS EN60950:2000
Updated Safety Requirements for IT & Telecoms Equipment Under the Low
Voltage Directive 
EN 60950:2000 was implemented at a national level on 1st January 2001,
replacing EN 60950 : 1992 including amendments:
1,2,3,4 and 11, which will be withdrawn in due course. EN 60950:2000 is a
harmonised standard under the Low Voltage Directive and as such compliance
with it provides a presumption of conformity with the essential requirements
of the Directive. The European Commission publishes dates for cessation of
the presumption of conformity, as shown below:
Amendment (A1) EN 60950 : 1992 1st March 2000 (Expired)
Amendment (A2) Amendment (A1) 1st March 2000 (Expired)
Amendment (A3) Amendment (A2) 1st January 2002
Amendment (A4) Amendment (A3) 1st August 2003
Amendment (A11) Amendment (A4) 1st August 2003
EN 60950 : 2000 Amendment (A11) 1st January 2005
What are the main differences between EN 60950 : 2000 and EN 60950 : 1992
inc amendments ?
The most obvious change in the new standard relates to the clause numbering,
which has been dramatically re-organised, but there are also a number of
amendments and additional requirements as follows:
Batteries
There is a requirement to consider, and in some cases test, any battery
installed in the equipment, (not just lithium batteries as previous). Also
manufacturers of equipment powered solely from an internal power source can
now use the relaxation under clause 4.4.5.2 covering the need for a fire
enclosure.
Protective Earthing / Bonding
Methods of determining the resistance of earthing conductors and their
minimum cross sectional areas have been added or modified. Also tests have
been made more onerous for the testing of earth conductors within equipment
rated in excess of 16A, and earth bonding conductors must be separated from
protective earthing conducters.
Opto-Isolators
Tests are now specified under clause 2.10.5.1. Also the distance through the
insulation for supplementary and reinforced insulation is relaxed under
certain circumstances.
Alternative Method for Determining Clearance 
Annex G provides an alternative method of determining clearance.
Mains Cords
The minimum designation for detachable mains cords is now the same for
equipment with a mass up to 3kg, irrespective of the total mass. Also the
cross sectional area of mains cords table has been expanded to include
higher currents.
Wiring Terminals 
Included in clause 3.3.6 are a number of constructional requirements for the
terminal supplied for the connection of permanently connected equipment or
equipment with ordinary non-detachable power cords.
10N, Steady Force Test
A new test has been added requiring components and parts to be subjected to
a 10N force.
Wall & Ceiling Mounted Equipment 
A force equal to 3 times the mass of the equipment or 50N (whichever is
greater) is now applied when the equipment is mounted on the wall or
ceiling, to ensure it does not become unstable.
Openings in Transportable Equipment
New requirements have been added addressing problems of foreign objects
entering equipment, e.g. lap top computers, from any orientation and being
subject to movement within the enclosure.
Leakage Currents to & from the Networks The standard addresses leakage
currents to and from the telecommunications networks and also considers
hazards which may arise as a result of leakage to or from multiple network
connections.
Flammability
A number of alternative methods of determining flammability have been added,
including the Glow Wire Test for components and parts located outside fire
enclosures.

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com


-Original Message-
From: duncan.ho...@snellwilcox.com [mailto:duncan.ho...@snellwilcox.com]
Sent: Tuesday, March 26, 2002 8:45 AM
To: emc-p...@majordomo.ieee.org
Subject: EN60950:1992 vs EN60950:2000



Group,
Does anyone have a list of all the differences between EN60950:1992 and
EN60950:2000? If so may I have a copy. 

Many thanks in advance
Duncan Hobbs.



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For help, s

Re: EN60950-1:2001

[John Woodgate]

I read in !emc-pstc that richwo...@tycoint.com wrote (in <846BF526A205F8
4BA2B6045BBF7E9A6A01F13E58@flbocexu05>) about 'EN60950-1:2001', on Wed,
20 Feb 2002:
>Is EN 60950-1:2001 the same as EN 60950:2000 but renumbered, or were changes
>introduced? 

No, there are significant differences.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero.
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: EN60950 - Changes between 1992 & 2000 Editions

[Allen, John]

Hi Folks

Many thanks to all who responded publically and privately to my enquiry.

Quite a number of comparison documents appear to exist in both the public
and private domains.

I will try to put together for the forum a brief summary of the various
sources of information sometime in the near future, but I will most
certainly respect any information that was given to me "privately".

It may be a month coming as I am very busy with projects and then on holiday
for a couple of weeks.
> 
> John Allen
> Thales Defence Communications Division 
> Bracknell
> UK
> 
> ---
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RE: EN60950 - Changes between 1992 & 2000 Editions

[Kazimier_Gawrzyjal]

Hi John,

I haven't seen it on any agency websites in soft form but I have seen a
cross referencing index in print about a year ago.  If you have a contact at
one of the agencies you might be able to get a copy.

If any agency participants on this forum have the go-ahead to share such an
index, I'm sure it would be much appreciated.

My opinion and not that of my employer.

Regards,
Kaz Gawrzyjal
kazimier_gawrzy...@dell.com

-Original Message-
From: Allan, James [mailto:james_al...@milgo.com]
Sent: Thursday, May 31, 2001 7:36 AM
To: 'Allen, John'; 'EMC-PSTC'
Subject: RE: EN60950 - Changes between 1992 & 2000 Editions



John:  If you can get a copy of Conformity for May 2001 there is a
comparison of UL 1950 3rd Ed with UL 60950.  This is not exactly what you
asked for but it may be 90% there.

http://www.conformity.com/

Jim Allan
Manager, Engineering Services
Milgo Solutions LLC
1619 N Harrison Parkway
Sunrise, FL, 33323
E-mail james_al...@milgo.com
Phone (954) 846-3720
Fax (954) 846-5693

> -Original Message-
> From: Allen, John [SMTP:john.al...@uk.thalesgroup.com]
> Sent: Thursday, May 31, 2001 6:12 AM
> To:   'EMC-PSTC'
> Subject:  EN60950 - Changes between 1992 & 2000 Editions
> 
> 
> Hi Folks
> 
> The requirements of the various clauses have been re-arranged between
> these
> two editions, so does anyone know of any guides or cross-references as to
> how the requirements have actually moved around?
> 
> Thanks in advance.
> 
> John Allen
> Thales Defence Communications Division 
> Bracknell
> UK
> 
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
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RE: EN60950 - Changes between 1992 & 2000 Editions

[Massey, Doug C.]

Hi John - check out http://www.ul.com/ite/60950Analysis_05_07_01.PDF for
UL's Certification Impact Analysis of the new standard. 

Doug Massey
LXE, Inc.

-Original Message-
From: Allen, John [mailto:john.al...@uk.thalesgroup.com]
Sent: Thursday, May 31, 2001 6:12 AM
To: 'EMC-PSTC'
Subject: EN60950 - Changes between 1992 & 2000 Editions



Hi Folks

The requirements of the various clauses have been re-arranged between these
two editions, so does anyone know of any guides or cross-references as to
how the requirements have actually moved around?

Thanks in advance.

John Allen
Thales Defence Communications Division 
Bracknell
UK

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RE: EN60950 - Changes between 1992 & 2000 Editions

[Allan, James]

John:  If you can get a copy of Conformity for May 2001 there is a
comparison of UL 1950 3rd Ed with UL 60950.  This is not exactly what you
asked for but it may be 90% there.

http://www.conformity.com/

Jim Allan
Manager, Engineering Services
Milgo Solutions LLC
1619 N Harrison Parkway
Sunrise, FL, 33323
E-mail james_al...@milgo.com
Phone (954) 846-3720
Fax (954) 846-5693

> -Original Message-
> From: Allen, John [SMTP:john.al...@uk.thalesgroup.com]
> Sent: Thursday, May 31, 2001 6:12 AM
> To:   'EMC-PSTC'
> Subject:  EN60950 - Changes between 1992 & 2000 Editions
> 
> 
> Hi Folks
> 
> The requirements of the various clauses have been re-arranged between
> these
> two editions, so does anyone know of any guides or cross-references as to
> how the requirements have actually moved around?
> 
> Thanks in advance.
> 
> John Allen
> Thales Defence Communications Division 
> Bracknell
> UK
> 
> ---
> This message is from the IEEE EMC Society Product Safety
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Re: EN60950 (UL1950, IEC 60950) On off switch marking.

[Ed Eszlari]

Rick,
If you are using IEC950 you can mark the switch I/O, if you are using IEC60065 you are only allowed to mark a single pole switch with the "I" (on) symbol. 
Ed

>From: "Rick Linford" 
>Reply-To: "Rick Linford" 
>To: 
>Subject: EN60950 (UL1950, IEC 60950) On off switch marking. 
>Date: Fri, 27 Apr 2001 10:25:19 -0600 
> 
> 
>Hi All, 
> 
>When a switch opens only one leg of the mains to control power to 
>equipment should it be marked with the "l" and "O"? 
> 
>Background: 
> 
>Three different engineers from three different NRTLs indicated it is 
>permitted, two even required it. A different engineer for one of the 
>NRTLs and two other respected individuals indicate it is prohibited. It 
>will be interesting if members of this list will have the same 50/50 
>split or if there is a correct answer. 
> 
>(single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be shipped US, 
>Canada, EU and generally internationally) 
> 
>To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown below. 
> 
>Where symbols are used on or near controls, for example switches, push 
>button, etc., to indicate "ON" "OFF" conditions, they shall be the line 
>l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and 
>60417-1-IEC-5008). For push-push type switches the symbol {line in side 
>the circle} shall be used (60417-1-IEC-5010). 
> 
>It is permitted to use the symbols O and l to indicate the "OFF" and 
>"ON" positions of any primary or secondary power switches, including 
>isolating switches. 
> 
>A "STAND-BY" condition shall be indicated by the symbol {line breaking 
>the circle at the top} (60417-1-IEC-5009). 
> 
>My bias was not included in the 50/50 statistics noted above but I 
>believe it is required. 
> 
>Rick Linford 
>Regulatory Engineer 
>SonicWALL 
> 
> 
>--- 
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RE: EN60950 (UL1950, IEC 60950) On off switch marking.

[Doug McKean]

I've worked on products which used triple phase 
inputs for different sections of the product and 
the main power ON/OFF breakers were usually barred 
together as one gang switch.  I also had off from 
one of those phases a motor which had it's own 
ON/OFF switch.  And all the switches were marked 
as "I/O". And that product passed testing for 
UL-1950 and EN60950. 

Not sure if that answers your question. 

Regards, Doug 


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RE: EN60950 (UL1950, IEC 60950) On off switch marking.

[Rick Linford]

Hi Scott,

The power cord acts as the disconnect.

Rick Linford 
SonicWALL

 -Original Message-
From:   Scott Barrows [mailto:sbarr...@curtis-straus.com] 
Sent:   Friday, April 27, 2001 12:41 PM
To: Rick Linford
Cc: emc-p...@majordomo.ieee.org
Subject:Re: EN60950 (UL1950, IEC 60950) On off switch marking.

Hi,
If the switch is being used as the disconnect device it needs to
disconnect
both poles simultaneously (2.6.6). 1.7.8.3 only refers to on and off
indications of the equipment.

So I guess I need to know if the switch is being used as a disconnect or
just to turn the machine on and off.

Scott Barrows
Curtis Straus LLC

Rick Linford wrote:

> Hi All,
>
> When a switch opens only one leg of  the mains to control power to
> equipment should it be marked with the "l" and "O"?
>
> Background:
>
> Three different engineers from three different NRTLs indicated it is
> permitted, two even required it. A different engineer for one of the
> NRTLs and two other respected individuals indicate it is prohibited.
It
> will be interesting if members of this list will have the same 50/50
> split or if there is a correct answer.
>
> (single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be shipped US,
> Canada, EU and generally internationally)
>
> To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown below.
>
> Where symbols are used on or near controls, for example switches, push
> button, etc., to indicate "ON" "OFF" conditions, they shall be the
line
> l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and
> 60417-1-IEC-5008). For push-push type switches the symbol {line in
side
> the circle} shall be used (60417-1-IEC-5010).
>
> It is permitted to use the symbols O and l to indicate the "OFF" and
> "ON" positions of any primary or secondary  power switches, including
> isolating switches.
>
> A "STAND-BY" condition shall be indicated by the symbol {line breaking
> the circle at the top} (60417-1-IEC-5009).
>
> My bias was not included in the 50/50 statistics noted above but I
> believe it is required.
>
> Rick Linford
> Regulatory Engineer
> SonicWALL
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
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>
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Re: EN60950 (UL1950, IEC 60950) On off switch marking.

[Scott Barrows]

Hi,
If the switch is being used as the disconnect device it needs to disconnect
both poles simultaneously (2.6.6). 1.7.8.3 only refers to on and off
indications of the equipment.

So I guess I need to know if the switch is being used as a disconnect or
just to turn the machine on and off.

Scott Barrows
Curtis Straus LLC

Rick Linford wrote:

> Hi All,
>
> When a switch opens only one leg of  the mains to control power to
> equipment should it be marked with the "l" and "O"?
>
> Background:
>
> Three different engineers from three different NRTLs indicated it is
> permitted, two even required it. A different engineer for one of the
> NRTLs and two other respected individuals indicate it is prohibited. It
> will be interesting if members of this list will have the same 50/50
> split or if there is a correct answer.
>
> (single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be shipped US,
> Canada, EU and generally internationally)
>
> To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown below.
>
> Where symbols are used on or near controls, for example switches, push
> button, etc., to indicate "ON" "OFF" conditions, they shall be the line
> l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and
> 60417-1-IEC-5008). For push-push type switches the symbol {line in side
> the circle} shall be used (60417-1-IEC-5010).
>
> It is permitted to use the symbols O and l to indicate the "OFF" and
> "ON" positions of any primary or secondary  power switches, including
> isolating switches.
>
> A "STAND-BY" condition shall be indicated by the symbol {line breaking
> the circle at the top} (60417-1-IEC-5009).
>
> My bias was not included in the 50/50 statistics noted above but I
> believe it is required.
>
> Rick Linford
> Regulatory Engineer
> SonicWALL
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
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>
> All emc-pstc postings are archived and searchable on the web at:
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Re: EN60950 (UL1950, IEC 60950) On off switch marking.

[Rich Nute]

Hi Rick:


There are three issues which we must address:

1.  The safety function of the switch.

2.  The safety function of all-pole disconnect
versus one-pole disconnect.

3.  The marking of the function of the switch.

*

The safety function of a disconnect device (for
which a switch is acceptable) is:

* to disconnect power in the event of some
  sort of safety incident within the 
  equipment;

* to disconnect power for the situation of
  servicing the equipment.

For cord-connected equipment, I alway designate
the plug or appliance coupler as the disconnect 
device.  This means that the power switch is not
an isolating switch.  This solves the problem of 
one-pole versus all-pole switch requirements, and 
contact separation requirements.

For the first function, a one-pole switch will
satisfy all safety incident situations except 
(50-50 chance) phase-to-ground fault (in which
case the building overcurrent devices provides
the protection).

For the second function, a one-pole switch 
satisfies the servicing situation for a 
polarized supply system with a polarized plug
and socket.  A one-pole switch does not satisfy
the servicing situation for a non-polarized 
supply system.  (However, the plug does satisfy
the servicing situation.)

In the situation you describe, you can designate
the plug (or appliance coupler) as the disconnect 
device, and the on-off switch as a functional 
(i.e. not a safety) switch.

According to the requirements you quoted, the "0"
and "1" symbols may be used on *any* primary power 
switch.  So, the symbols may be used on either a 
functional switch or an isolating switch.

For marking, there is no requirement that the "0" 
and "1" symbols are restricted to isolating 
switches.  However, isolating switches must be
marked with the "0" and "1" symbols.

Most of our products do not have a primary power
switch.  We use a secondary circuit functional 
on-off switch.  Since we do not switch primary 
power, we do not use the "0" symbol, but the 
"stand-by" symbol.


Best regards,
Rich




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RE: EN60950 (UL1950, IEC 60950) On off switch marking.

[WOODS]

I hit the send button too soon. I forgot to mention the standby symbol. I
added that below.


Rick, let's start with the general requirement per clause 1.7.8.1.
The requirement is "Unless it is obviously unnecessary, indicators, switches
and other controls affecting safety shall be identified or placed so as to
indicate clearly which function they control. Indications used for this
purpose shall, wherever practicable, be comprehensible without a knowledge
of languages, national standards, etc."  

Does the switch in question affect safety? Since the switch performs
a power on/off function, I would say yes. Are the "on" and "off" positions
of the switch understandable without markings? Probably not, so some kind of
marking is required and the type is specified by clause 1.7.8. as the famous
"I" and "O" (or the push button symbol or standby symbol).

Is it allowed to mark a power switch that only switches one side of
the mains? Yes, the marking is permitted by clause 1.7.8.3 to be applied to
"any primary power switches."

Putting all of this together, the answer is yes, marking is both
permitted and required on your power switch. 

But, do you use the "OFF" or the "standby" marking symbol? A main
disconnect device (breaks all poles and has 3 mm spacings) may use the "O".
All other types of on/off switches may use the "standby" marking since the
use of the "O" marking would be misleading to the service person and create
a potential hazard during servicing. This is your case since you cannot
guarantee that the unswitched pole will be an earthed neutral.

So, the short answer is that the "I" and "Standby" markings are
required for your product.

Richard Woods

--
From:  Rick Linford [SMTP:rlinf...@sonicwall.com]
Sent:  Friday, April 27, 2001 12:25 PM
To:  emc-p...@majordomo.ieee.org
Subject:  EN60950 (UL1950, IEC 60950) On off switch marking.


Hi All,

When a switch opens only one leg of  the mains to control
power to
equipment should it be marked with the "l" and "O"? 

Background:

Three different engineers from three different NRTLs
indicated it is
permitted, two even required it. A different engineer for
one of the
NRTLs and two other respected individuals indicate it is
prohibited. It
will be interesting if members of this list will have the
same 50/50
split or if there is a correct answer.

(single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be
shipped US,
Canada, EU and generally internationally)

To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown
below.

Where symbols are used on or near controls, for example
switches, push
button, etc., to indicate "ON" "OFF" conditions, they shall
be the line
l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and
60417-1-IEC-5008). For push-push type switches the symbol
{line in side
the circle} shall be used (60417-1-IEC-5010).

It is permitted to use the symbols O and l to indicate the
"OFF" and
"ON" positions of any primary or secondary  power switches,
including
isolating switches.

A "STAND-BY" condition shall be indicated by the symbol
{line breaking
the circle at the top} (60417-1-IEC-5009).

My bias was not included in the 50/50 statistics noted above
but I
believe it is required.

Rick Linford
Regulatory Engineer
SonicWALL


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Hall,"

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RE: EN60950 (UL1950, IEC 60950) On off switch marking.

[WOODS]

Rick, let's start with the general requirement per clause 1.7.8.1. The
requirement is "Unless it is obviously unnecessary, indicators, switches and
other controls affecting safety shall be identified or placed so as to
indicate clearly which function they control. Indications used for this
purpose shall, wherever practicable, be comprehensible without a knowledge
of languages, national standards, etc."  

Does the switch in question affect safety? Since the switch performs a power
on/off function, I would say yes. Are the "on" and "off" positions of the
switch understandable without markings? Probably not, so some kind of
marking is required and the type is specified by clause 1.7.8. as the famous
"I" and "O" (or the push button symbol or standby symbol).

Is it allowed to mark a power switch that only switches one side of the
mains? Yes, the marking is permitted by clause 1.7.8.3 to be applied to "any
primary power switches."

Putting all of this together, the answer is yes, the marking is both
permitted and required on your power switch.


Richard Woods

--
From:  Rick Linford [SMTP:rlinf...@sonicwall.com]
Sent:  Friday, April 27, 2001 12:25 PM
To:  emc-p...@majordomo.ieee.org
Subject:  EN60950 (UL1950, IEC 60950) On off switch marking.


Hi All,

When a switch opens only one leg of  the mains to control power to
equipment should it be marked with the "l" and "O"? 

Background:

Three different engineers from three different NRTLs indicated it is
permitted, two even required it. A different engineer for one of the
NRTLs and two other respected individuals indicate it is prohibited.
It
will be interesting if members of this list will have the same 50/50
split or if there is a correct answer.

(single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be shipped
US,
Canada, EU and generally internationally)

To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown below.

Where symbols are used on or near controls, for example switches,
push
button, etc., to indicate "ON" "OFF" conditions, they shall be the
line
l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and
60417-1-IEC-5008). For push-push type switches the symbol {line in
side
the circle} shall be used (60417-1-IEC-5010).

It is permitted to use the symbols O and l to indicate the "OFF" and
"ON" positions of any primary or secondary  power switches,
including
isolating switches.

A "STAND-BY" condition shall be indicated by the symbol {line
breaking
the circle at the top} (60417-1-IEC-5009).

My bias was not included in the 50/50 statistics noted above but I
believe it is required.

Rick Linford
Regulatory Engineer
SonicWALL


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RE: EN60950 (UL1950, IEC 60950) On off switch marking.

[Ned Devine]

Hi,

Well here is the other side to keep it 50-50.

I have understood the requirement to be that the "O" symbol can only be used
when all power has been disconnected from the unit.  I believe that if you
used a single pole switch on a grounded neutral system, it would be OK.  Of
course, this is only OK if you can be sure that you know which will be the
neutral.  

Ned


Ned Devine
Program Manager III
Entela, Inc.
3033 Madison Ave. SE
Grand Rapids, MI  49548

616 248 9671 Phone
616 574 9752 Fax
ndev...@entela.com  e-mail




-Original Message-
From: geor...@lexmark.com [mailto:geor...@lexmark.com]
Sent: Friday, April 27, 2001 12:47 PM
To: Rick Linford
Cc: emc-p...@majordomo.ieee.org
Subject: Re: EN60950 (UL1950, IEC 60950) On off switch marking.





Rick,

My opinion based on my understanding of IEC 60950.

Whether an on/off switch breaks one or both sides of the line, the
equipment will be either on or off respectively, as either breaks the
electron path.

It is true that breaking only one side may leave the electronics "hot"
if the plug or socket allow for the neutral to be the "open" side.  However,
the device will be off.

As I recall, the marking instructions you referenced make no mention of
whether one or both of the mains leads are opened by the switch.  Therefore,
the "I" or "O" apply only to whether the device is on or off, which results
from
breaking either or both sides of the line.

George Alspaugh
Lexmark International Inc.




"Rick Linford"  on 04/27/2001
12:25:19 PM

Please respond to "Rick Linford"


To:   emc-pstc%majordomo.ieee@interlock.lexmark.com
cc:(bcc: George Alspaugh/Lex/Lexmark)
Subject:  EN60950 (UL1950, IEC 60950) On off switch marking.




Hi All,

When a switch opens only one leg of  the mains to control power to
equipment should it be marked with the "l" and "O"?

Background:

Three different engineers from three different NRTLs indicated it is
permitted, two even required it. A different engineer for one of the
NRTLs and two other respected individuals indicate it is prohibited. It
will be interesting if members of this list will have the same 50/50
split or if there is a correct answer.

(single phase 100 to 240 VAC, 2A, 50-60 Hz, intended to be shipped US,
Canada, EU and generally internationally)

To help, IEC 60950 (1999), section 1.7.8.3 Symbols, is shown below.

Where symbols are used on or near controls, for example switches, push
button, etc., to indicate "ON" "OFF" conditions, they shall be the line
l for "ON" and the circle O for "OFF" (60417-1-IEC-5007 and
60417-1-IEC-5008). For push-push type switches the symbol {line in side
the circle} shall be used (60417-1-IEC-5010).

It is permitted to use the symbols O and l to indicate the "OFF" and
"ON" positions of any primary or secondary  power switches, including
isolating switches.

A "STAND-BY" condition shall be indicated by the symbol {line breaking
the circle at the top} (60417-1-IEC-5009).

My bias was not included in the 50/50 statistics noted above but I
believe it is required.

Rick Linford
Regulatory Engineer
SonicWALL




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