Re: Bad Fuse vs. Good Fuse

[Rich Nute]

Hi Dan:


Thank you for giving us straight answers and helping us
to overcome the "conventional wisdom" about fuses.

Several years ago, I put together an article addressing
fuses, their operation, and how to select the fuse rating.
See:

http://www.ewh.ieee.org/soc/emcs/pstc/psn/

Then, download file 90v03n3.pdf.

Clearly, this is out of date, but the principles I believe
are still valid.


Best regards,
Rich





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Importing Unfinished Goods to the United States

[Bob Zmudka]

Can anyone provide me with guidance on how to import unfinished goods to the
US.  The product is a Telco attached digital device so FCC Parts 15 and 68
apply.  The plan is to import the product with out any labeling.  Before the
product is shipped to the customer it will be programmed with a customized
SW load with the desired feature set and then labeled to identify its
configuration which will also bear the FCC markings.  I'm trying to identify
what kind of documentation is required by customs to allow entry.

Thanks,
Bob Zmudka


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Re: Bad Fuse vs. Good Fuse

[Fred Townsend]

Dan I agree in general with your comments.  I will go so far as to stipulate
many design engineers don't know their hole from an ass in the ground as far
as properly specifying fuses. That being said the fuse industry has a problem. 

I have seen many, genuinely defective fuses.  I have seen even more genuinely
defective fuse holders that make the fuse appear defective.  Fuse holders that
were so hot they melted the fuse because they had several ohms of contact
resistance caused by the holder manufacture not properly cleaning them. 


I am happy to state that 99.5% of the problems I have seen were not with Buss
fuses. The vast majority of problems lie with your competitors that undersell
Buss.  Purchasing thinks a fuse is a fuse is a fuse and buys the cheaper fuse.
How about some guaranteed AQL levels that the engineers can specify to keep
the bad guys out of the purchasing office?  Is there an IEEE group for fuses? 
Maybe there should be. 


Fred Townsend 


"Giblin, Dan" wrote: 


  

As a fuse manufacturer, I have read all the e-mail on this subject with great
interest.  Unfortunately, many responses emphasize common misunderstandings. 


In the fuse industry, there is no such thing as a "Bad" fuse.  The chain of
e-mails clearly indicate why we avoid this word due to its various meanings. 
Similarly, we try to avoid the word 'failure'.  A "bad" or 'failed' fuse can
mean any number of things, but the most common is that the fuse is open, (it
operated).  Thus, the fuse did what it was supposed to do - operate - and yet
it is deemed 'bad' or a 'failure'. 


There are numerous occasions when a customer returns a 'bad' fuse.  The fuse
was 'bad' because it operated properly.  In many instances, the choice of fuse
type or amperage rating was flawed. 


For being such a 'simple' device, there are many items that influence the
correct choice.  I will address some of these by picking quotes out of the
various e-mail on the subject.  Among these are: 


*   Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've 
heard
of a "bad" fuse, in this case, a fuse not adequate to protect the circuit and
user.  A 30 volt fuse can't be counted on to interrupt a 408 volt circuit. 
This is absolutely correct.  Choosing a voltage rating below your application
can be very dangerous.
*   Continuous Current rating  - This was addressed in Mr. Beckwith's 
e-mail -
Fuse operation when there is no fault can also sometimes be caused by
incorrect specification at the design stage, i.e. the fuse is rated too low
for the actual current consumed.  Very true.  One must look at surges
mentioned below and temperature.
*   Temporary Surges that you want the fuse to pass - A time delay fuse is
typically chosen for motor or transformer applications.  This is addressed a
little in Mr. Beckwith's e-mail - We have all seen cases where a fuse blows
when there is no apparent fault in the equipment, hence the maintainer's
comment "bad fuse". In my experience, this is usually caused by a temporary
overload condition or a power surge, not a "bad" fuse.
*   Temporary Surges that you do not want the fuse to pass.
*   Ambient temperature rating - This was addressed in Mr. Hughes e-mail 
below.
*   Interrupting Rating - This was addressed in Mr. Hughes e-mail - A 
couple of
other common design drop-offs I would like to mention include failure to
select a fuse with an adequate prospective fault current (i.e. selecting a
5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit
where the prospective fault is in the order of 1kA) and 'forgetting' to
de-rate the fuse for use in a high ambient temperature (although this has
already be mentioned re. pico-fuses). 
*   Shock/Vibration - Most fuses do not claim to be suitable for such
applications.  From Mr. Schlentz - I have seen one instance where a fuse
opened during a vibration test.  I think that was a BAD FUSE.  I don't know if
the fuse in question was supposed to be suitable or not.

If chosen incorrectly, and 'nuisance' opening occurs, as Mr. Powell mentions -
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.  In doing this, you may be defeating
the purpose of having the protection there in the first place.  If a fuse
nuisance opens, it is likely that one of the above bulleted items was
overlooked. 


Additionally, as Mr. Richmond points out - Many fuses ARE mechanically
fragile; it's simple physics that says a low-current fuse will be a fragile
thread.  Think of them as light bulbs.  We do not call a light bulb unreliable
if it fails after being dropped on the floor; we call it broken.  This is
particularly true for low amperage fuses. 


As Mr. Beckwith points out - AIUI, there is a specified time it takes the fuse
to operate at 200% of the rated current, so for example a 1A normal blow fuse
requires 2A for 

RE: ESD Problem

[Mike Hopkins]

So is mine (hand up, that is)

Best Regards,

Michael Hopkins
Manager, EMC Technologies
Thermo Electron
Control Technology Division
EMC & ESD Simulation Systems
One Lowell Research Center
Lowell, MA 01852
Tel: +1 978 275 0800 ext. 334
Fax: +1 978 275 0850
michael.hopk...@thermo.com

One Thermo, committed to integrity, intensity, innovation and involvement



From: Pommerenke, David [mailto:davi...@umr.edu]
Sent: Tuesday, May 27, 2003 11:16 AM
To: Luke Turnbull; emc-p...@ieee.org
Subject: RE: ESD Problem



My hand is up.

David Pommerenke


From: Luke Turnbull [mailto:luke.turnb...@trw.com] 
Sent: Tuesday, May 27, 2003 8:23 AM
To: emc-p...@ieee.org
Subject: ESD Problem


Would the gentleman who is on the 61000-4-2 committee please put his
hand up?

Thanks,

Luke Turnbull




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RE: AC shut-down

[Sam Davis]

I can't confirm or deny the requirement, but I wouldn't say it's a bad idea.
Often, fire suppression systems can be assisted by shutting off airflow.
Chemical or biological agents, when used, will likely target the air
handling system, for maximum effectiveness.  It wouldn't save a building
>from another 9/11 attack, but building codes can't do much in that arena.

I'm not saying it's a good idea to require this be added to the building
codes, but I'd rather see a server room go down than a life.

Sam


From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of John Woodgate
Sent: Friday, May 23, 2003 3:23 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: AC shut-down



I read in !emc-pstc that simon_...@emc.com wrote (in <277DD60FB639D511AC
0400b0d068b71e0b435...@corpmx14.corp.emc.com>) about 'AC shut-down' on
Fri, 23 May 2003:
>I wonder if anybody can substantiate or debunk a rumor that in New York
>City, and maybe in New York State, there is a new requirement to shut off
>air conditioning systems in buildings in case of emergency, a post 9/11
>measure.  It is an important issue: Since the computer systems can continue
>to function, the computer room temperature can quickly shoot up to as high
>as 140F (60C), there maybe no risk of fire, but a multimillion system can
>overheat and self-destruct.

It sounds like 'military intelligence' to me. (;-)
--
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: Bad Fuse vs. Good Fuse

[fdev...@assaabloyitg.com]

Dan,

So far there hasn't been mention of the mechanical stress aspect of fuse
failure related to the fuse wire breaking because of repeated cycling of
power.  I have personally seen this happen at a commercial daytime radio
station.  It took over a year for a properly rated fuse to blow because the
transmitter was turned on and off daily; the fuse wire was simply
mechanically flexed because of slight heating and finally went.  Yes, it
blew again about a year after it was replaced.  Maybe the transmitter
manufacturer should have specified a slow-blow fuse.

Frank de Vall
Manager Compliance Engineering
Assa Abloy ITG & HID Corporation



  

  "Giblin, Dan"   

  To:  
"'emc-p...@majordomo.ieee.org'"  
  Sent by:  
, "'POWELL, DOUG'"   
  owner-emc-pstc@majordo 

  mo.ieee.org   cc:   

Subject:  RE: Bad Fuse vs.
Good Fuse   
  

  05/27/2003 02:17 PM 

  Please respond to   

  "Giblin, Dan"   

  

  







As a fuse manufacturer, I have read all the e-mail on this subject with
great interest.  Unfortunately, many responses emphasize common
misunderstandings.

In the fuse industry, there is no such thing as a "Bad" fuse.  The chain of
e-mails clearly indicate why we avoid this word due to its various
meanings.  Similarly, we try to avoid the word 'failure'.  A "bad" or
'failed' fuse can mean any number of things, but the most common is that
the fuse is open, (it operated).  Thus, the fuse did what it was supposed
to do - operate - and yet it is deemed 'bad' or a 'failure'.

There are numerous occasions when a customer returns a 'bad' fuse.  The
fuse was 'bad' because it operated properly.  In many instances, the choice
of fuse type or amperage rating was flawed.

For being such a 'simple' device, there are many items that influence the
correct choice.  I will address some of these by picking quotes out of the
various e-mail on the subject.  Among these are:

   Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've
   heard of a "bad" fuse, in this case, a fuse not adequate to protect the
   circuit and user.  A 30 volt fuse can't be counted on to interrupt a 408
   volt circuit.  This is absolutely correct.  Choosing a voltage rating
   below your application can be very dangerous.

   Continuous Current rating  - This was addressed in Mr. Beckwith's e-mail
   - Fuse operation when there is no fault can also sometimes be caused by
   incorrect specification at the design stage, i.e. the fuse is rated too
   low for the actual current consumed.  Very true.  One must look at
   surges mentioned below and temperature.

   Temporary Surges that you want the fuse to pass - A time delay fuse is
   typically chosen for motor or transformer applications.  This is
   addressed a little in Mr. Beckwith's e-mail - We have all seen cases
   where a fuse blows when there is no apparent fault in the equipment,
   hence the maintainer's comment "bad fuse". In my experience, this is
   usually caused by a temporary overload condition or a power surge, not a
   "bad" fuse.

   Temporary Surges that you do not want the fuse to pass.

   Ambient temperature rating - This was addressed in Mr. Hughes e-mail
   below.

   Interrupting Rating - This was addressed in Mr. Hughes e-mail - A couple
   of other common design drop-offs I would like to mention include failure
   to select a fuse with an adequate prospective fault current (i.e.
   selecting a 5x20 mm glass fuse - rated at Isc=35A max and using it in a
   mains circuit where the prospective fault is in the order of 1kA) and
   'forgetting' to de-rate the fuse for use in a high ambient temperature
   (although this has already be mentioned re. pico-fuses).

   Shock/Vibration - Most fuses do not claim to be suitable for such
   applications.  From Mr. Schlentz - I have seen one instance where a fuse
   opene

New SBC NEBS Requirements Document

[Dave Lorusso]

SBC has a new issue of their NEBS document TP76200 on their web site:
 
https://ebiznet.sbc.com/sbcnebs/
 
You can also find a link to it and other RBOC checklists at:
 
http://nebs-faq.com/do_the_rbocs_have_requirements_over.htm
 
Of note is SBC’s acceptance of ANSI/T1.319-2002 for Fire Resistance testing.
 Tests performed to the May 2002 issue will be accepted until the end of
September.
 
Best regards,
 
Dave Lorusso
Lorusso Technologies, LLC 
1200 Mahogany Lane
P. O. Box 3756
Cedar Park, TX 78630-3756
“Your NEBS, Product Safety and EMC Solution”
www.lorusso.com  

RE: Bad Fuse vs. Good Fuse

[Giblin, Dan]

As a fuse manufacturer, I have read all the e-mail on this subject with great
interest.  Unfortunately, many responses emphasize common misunderstandings.

In the fuse industry, there is no such thing as a "Bad" fuse.  The chain of
e-mails clearly indicate why we avoid this word due to its various meanings. 
Similarly, we try to avoid the word 'failure'.  A "bad" or 'failed' fuse can
mean any number of things, but the most common is that the fuse is open, (it
operated).  Thus, the fuse did what it was supposed to do - operate - and yet
it is deemed 'bad' or a 'failure'.

There are numerous occasions when a customer returns a 'bad' fuse.  The fuse
was 'bad' because it operated properly.  In many instances, the choice of fuse
type or amperage rating was flawed.

For being such a 'simple' device, there are many items that influence the
correct choice.  I will address some of these by picking quotes out of the
various e-mail on the subject.  Among these are:

*   Voltage rating - (This was addressed in Mr. Richmond's e-mail - I've 
heard
of a "bad" fuse, in this case, a fuse not adequate to protect the circuit and
user.  A 30 volt fuse can't be counted on to interrupt a 408 volt circuit. 
This is absolutely correct.  Choosing a voltage rating below your application
can be very dangerous. 

*   Continuous Current rating  - This was addressed in Mr. Beckwith's 
e-mail -
Fuse operation when there is no fault can also sometimes be caused by
incorrect specification at the design stage, i.e. the fuse is rated too low
for the actual current consumed.  Very true.  One must look at surges
mentioned below and temperature.

*   Temporary Surges that you want the fuse to pass - A time delay fuse is
typically chosen for motor or transformer applications.  This is addressed a
little in Mr. Beckwith's e-mail - We have all seen cases where a fuse blows
when there is no apparent fault in the equipment, hence the maintainer's
comment "bad fuse". In my experience, this is usually caused by a temporary
overload condition or a power surge, not a "bad" fuse.

*   Temporary Surges that you do not want the fuse to pass.

*   Ambient temperature rating - This was addressed in Mr. Hughes e-mail 
below. 

*   Interrupting Rating - This was addressed in Mr. Hughes e-mail - A 
couple of
other common design drop-offs I would like to mention include failure to
select a fuse with an adequate prospective fault current (i.e. selecting a
5x20 mm glass fuse - rated at Isc=35A max and using it in a mains circuit
where the prospective fault is in the order of 1kA) and 'forgetting' to
de-rate the fuse for use in a high ambient temperature (although this has
already be mentioned re. pico-fuses).  

*   Shock/Vibration - Most fuses do not claim to be suitable for such
applications.  From Mr. Schlentz - I have seen one instance where a fuse
opened during a vibration test.  I think that was a BAD FUSE.  I don't know if
the fuse in question was supposed to be suitable or not.

  

If chosen incorrectly, and 'nuisance' opening occurs, as Mr. Powell mentions -
Often the answer is, increase the fuse size to prevent nuisance trips.  The
risk, of course, is that for every incremental increase in fuse value, you
increase the risk of fire proportionally.  In doing this, you may be defeating
the purpose of having the protection there in the first place.  If a fuse
nuisance opens, it is likely that one of the above bulleted items was
overlooked.

Additionally, as Mr. Richmond points out - Many fuses ARE mechanically
fragile; it's simple physics that says a low-current fuse will be a fragile
thread.  Think of them as light bulbs.  We do not call a light bulb unreliable
if it fails after being dropped on the floor; we call it broken.  This is
particularly true for low amperage fuses. 

As Mr. Beckwith points out - AIUI, there is a specified time it takes the fuse
to operate at 200% of the rated current, so for example a 1A normal blow fuse
requires 2A for approximately 10 seconds to go open circuit.  This time
reduces exponentially as the current increases.  There are different opening
time requirements depending on the type of fuse, (Time Delay versus Fast
Acting), and its physical size.  The 135%, 200% and/or 500% opening times are
documented in the tri-national, harmonized 248 Series of fuse Standards,
(248.1 through 248.16 - The standards are UL, CSA, and ANCE).   

If anyone has any specific questions, or would like more information, send me
a separate e-mail and I'll see what I can do.

Dan 

Manager, Industry Standards & Certifications 
Cooper Bussmann 

RMCEMC SI/EMC Presentation slides available for download

[Grasso, Charles]

To all interested parties:

The presentation slides from our May 13th meeting:

Signal Integrity/EMI Challenges & Design Solutions - A Seminar

is now available for download from our website at
http://www.ieee.org/rmcemc

Thank you

Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel:  303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: charles.gra...@echostar.com;  
Email Alternate: chasgra...@ieee.org


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RE: Bad Fuse vs. Good Fuse

[Stone, Richard]

seems this Fuse thing may need to be Dis-Fused..
99.99% of time their probably made correctly and thus
blow per their intended current..
its possible one was mfr'rd wrong/bad.
thus not working correctly..
which could be a problem for the user.
hope this stop before someone blows
his/her fuse...
only thing I have ever seen is the wrong fuse
used, that didnt blow..but the right fuse always did.
Richard,


From: don_borow...@selinc.com [mailto:don_borow...@selinc.com]
Sent: Tuesday, May 27, 2003 11:31 AM
To: EMC-PSTC (E-mail)
Subject: Re: Bad Fuse vs. Good Fuse








This seems to be a problem of semantics. In the case of a fuse, a "failure"
is a success - the fuse succeeded in protecting the circuit (neglecting the
cases where the fuse failed to do its job, discussed elsewhere).

I clearly recall some ads for Timken Steel in the 1960s which discussed the
successful "failure" of a mechanical "fuse", a device that would restrain
jets on the deck of an aircraft carrier until the engine thrust and
catapult force built up sufficiently for a safe launch, at which point the
device broke.

The problem is that in many cases when a metal part breaks, it is indeed a
failure. The same language gets carried across to cases where breakage is
the desired result, as in the case of the mechanical "fuse" where its
breaking is an indication things going well.

In the case of fuse operation, things are not going well. There is some
problem. The blown fuse is associated with a true failure. So perhaps there
is some guilt by association, even though the fuse is the (desired) victim
of the true failure.

I like the term "blown fuse". Though perhaps it is not as exact a
descrition as one would like, it is broadly understood, and is not
necessarily associated with failure or a "bad" fuse.

Don Borowski
Schweitzer Engineering Labs
Pullman, WA  USA

owner-emc-p...@majordomo.ieee.org wrote on 05/23/2003 03:56:53 PM:

> Hello all,
>
> Recently, in my company, we've been discussing what exactly
> constitutes a good or bad fuse.  In this industry we often hear that
> the trouble with a defective product was, "the fuse was bad."  I
> occurred to me that the fuse is not bad, it performed exactly
> intended.  In fact if the problem that caused the fuse to "operate"
> is still present, then the fuse is still good even though it is now
> an open circuit.  The only time it can be a bad fuse is if it did
> not operate, resulting in shock or a fire.
>
> I have now have my ears tuned-in to this concept of a "bad fuse" and
> find it is commonly used all over the industry.  In fact you can go
> to any number of websites that provide trouble shooting notes, and
> find instructions on how you can measure a bad fuse from a good fuse
> using an Ohm meter, photos included.  And some of these instructions
> are from reputable manufacturers.  Another term often used is
> "defective fuse", which in some way sounds more scientific, but is
> still fundamentally wrong.
>
> I recently saw a newspaper article that gave the explaination why
> electrical service was lost for over 100,000 people as a bad fuse.
> An investigation was under way to determine why the fuse went bad.
> This is a little like hearing the technologically uninitiated say
> "it must be a short somewhere", when the television set stops working.
>
> Maybe I am finicky, but this affects how companies view real product
> defects.  When the "defect" is the bad fuse, then the real problem
> may be covered up.  Often the answer is, increase the fuse size to
> prevent nuisance trips.  The risk, of course, is that for every
> incremental increase in fuse value, you increase the risk of fire
> proportionally.
>
> Any thoughts or experiences?
>
> BTW - To all US citizens in the group, have a relaxing Memorial Day
weekend.
>
>
> -doug
>
> Douglas E. Powell
> Regulatory Compliance Engineer
> Advanced Energy Industries, Inc.
> Fort Collins, CO 80535 USA



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Re: Harmonics and conducted emissions

[John Woodgate]

I read in !emc-pstc that Pettit, Ghery  wrote
(in <42050df556283a4d977b111eb7063208138...@orsmsx407.jf.intel.com>)
about 'Harmonics and conducted emissions' on Tue, 27 May 2003:

>EN 61000-3-2, by definition, is unhelpful.  End of editorial comment.

That's a bit harsh. IEC/EN 61000-3-2 expect the use of the measuring
device described in IEC/EN 61000-4-7. This does not measure 'conducted
emissions' in the CISPR sense.

I don't see how 61000-3-2 can be 'helpful' on a subject outside its
scope, but if you have a proposal I will suggest how you can get it
taken into account for the planned full revision of 61000-3-2.
-- 
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: Bad Fuse vs. Good Fuse

[garymcintu...@aol.com]

(from Cambridge Advanced Learner's Dictionary
 )
bad (LOW QUALITY) adjective worse, worst
low quality; not acceptable:

Re: Bad Fuse vs. Good Fuse

[don_borow...@selinc.com]

This seems to be a problem of semantics. In the case of a fuse, a "failure"
is a success - the fuse succeeded in protecting the circuit (neglecting the
cases where the fuse failed to do its job, discussed elsewhere).

I clearly recall some ads for Timken Steel in the 1960s which discussed the
successful "failure" of a mechanical "fuse", a device that would restrain
jets on the deck of an aircraft carrier until the engine thrust and
catapult force built up sufficiently for a safe launch, at which point the
device broke.

The problem is that in many cases when a metal part breaks, it is indeed a
failure. The same language gets carried across to cases where breakage is
the desired result, as in the case of the mechanical "fuse" where its
breaking is an indication things going well.

In the case of fuse operation, things are not going well. There is some
problem. The blown fuse is associated with a true failure. So perhaps there
is some guilt by association, even though the fuse is the (desired) victim
of the true failure.

I like the term "blown fuse". Though perhaps it is not as exact a
descrition as one would like, it is broadly understood, and is not
necessarily associated with failure or a "bad" fuse.

Don Borowski
Schweitzer Engineering Labs
Pullman, WA  USA

owner-emc-p...@majordomo.ieee.org wrote on 05/23/2003 03:56:53 PM:

> Hello all,
>
> Recently, in my company, we've been discussing what exactly
> constitutes a good or bad fuse.  In this industry we often hear that
> the trouble with a defective product was, "the fuse was bad."  I
> occurred to me that the fuse is not bad, it performed exactly
> intended.  In fact if the problem that caused the fuse to "operate"
> is still present, then the fuse is still good even though it is now
> an open circuit.  The only time it can be a bad fuse is if it did
> not operate, resulting in shock or a fire.
>
> I have now have my ears tuned-in to this concept of a "bad fuse" and
> find it is commonly used all over the industry.  In fact you can go
> to any number of websites that provide trouble shooting notes, and
> find instructions on how you can measure a bad fuse from a good fuse
> using an Ohm meter, photos included.  And some of these instructions
> are from reputable manufacturers.  Another term often used is
> "defective fuse", which in some way sounds more scientific, but is
> still fundamentally wrong.
>
> I recently saw a newspaper article that gave the explaination why
> electrical service was lost for over 100,000 people as a bad fuse.
> An investigation was under way to determine why the fuse went bad.
> This is a little like hearing the technologically uninitiated say
> "it must be a short somewhere", when the television set stops working.
>
> Maybe I am finicky, but this affects how companies view real product
> defects.  When the "defect" is the bad fuse, then the real problem
> may be covered up.  Often the answer is, increase the fuse size to
> prevent nuisance trips.  The risk, of course, is that for every
> incremental increase in fuse value, you increase the risk of fire
> proportionally.
>
> Any thoughts or experiences?
>
> BTW - To all US citizens in the group, have a relaxing Memorial Day
weekend.
>
>
> -doug
>
> Douglas E. Powell
> Regulatory Compliance Engineer
> Advanced Energy Industries, Inc.
> Fort Collins, CO 80535 USA



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RE: ESD Problem

[Pommerenke, David]

My hand is up.

David Pommerenke


From: Luke Turnbull [mailto:luke.turnb...@trw.com] 
Sent: Tuesday, May 27, 2003 8:23 AM
To: emc-p...@ieee.org
Subject: ESD Problem


Would the gentleman who is on the 61000-4-2 committee please put his
hand up?

Thanks,

Luke Turnbull




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RE: Harmonics and conducted emissions

[Pettit, Ghery]

Neil,

The "out of band" emissions below 150 kHz are nothing new.  I remember
having this problem when testing to the old German standards that had us
performing power line conducted emissions tests down to 9 kHz.  The
noise off the input rectifiers would saturate the front end of a
spectrum analyzer, causing it to read low.  A receiver with adequate
pre-selection or a filter were the only options for accurate
measurements.

EN 61000-3-2, by definition, is unhelpful.  End of editorial comment.

Ghery Pettit



From: Neil Helsby [mailto:nei...@solid-state-logic.com] 
Sent: Tuesday, May 27, 2003 3:34 AM
To: emc-p...@majordomo.ieee.org
Subject: Harmonics and conducted emissions


Has anyone else noticed the tendency of modern switch mode power supply 
designers to save manufacturing costs at the expense of harmonic and 
conducted emissions measurements?

EN 61000-3-2:2000 has introduced the concept of Partial Odd Harmonics
for the 21st and above. While this adds extra functions to the
spread-sheet 
results check, I wonder if it also has an unhelpful side effect.

With conducted emissions, new power supply designs generate peak 
emissions at frequencies below 200 KHz that increase in level inversely 
to the frequency. These out-of-band emissions result in overloading the 
front-end of a Spectrum Analyser that consequently requires either a 
pre-selector or calibrated filter to function correctly. There is, of 
course, the alternative of purchasing a new receiver!

Neil Helsby


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ESD Problem

[Luke Turnbull]

Would the gentleman who is on the 61000-4-2 committee please put his hand up?

Thanks,

Luke Turnbull




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Re: Harmonics and conducted emissions

[Cortland Richmond]

Neil Helsby wrote:

>> Has anyone else noticed the tendency of modern switch mode power supply 
designers to save manufacturing costs at the expense of harmonic and 
conducted emissions measurements?<<

It's not "modern." I ran into it in the 1980's. Saving costs isn't _bad_,
mind; it's simply doing only what's needed to get the job done. OUR job --
among other things -- is to be sure PS designers know EMI is part of that,
and help them include it at the lowest cost, too.

Cortland


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Re: Harmonics and conducted emissions

[John Woodgate]

I read in !emc-pstc that Neil Helsby 
wrote (in <20030527.10334...@mis.configured.host>) about 'Harmonics and
conducted emissions' on Tue, 27 May 2003:

>Has anyone else noticed the tendency of modern switch mode power supply 
>designers to save manufacturing costs at the expense of harmonic and 
>conducted emissions measurements?

Did you mean to write 'measurements' in that sentence? It doesn't make
sense, really.
>
>EN 61000-3-2:2000 has introduced the concept of Partial Odd Harmonics for the 
>21st and above. While this adds extra functions to the spread-sheet 
>results check, I wonder if it also has an unhelpful side effect.

I don't see that this is necessarily relevant to the next paragraph,
about conducted emissions, which are still mostly measured from 150 kHz
upwards. The 'partial odd harmonics' thing deals with harmonics up to
the 39th only. That's 1950 Hz in Europe and 2340 Hz in the Americas. Are
you measuring conducted emissions down to 9 kHz? 
>
>With conducted emissions, new power supply designs generate peak 
>emissions at frequencies below 200 KHz that increase in level inversely 
>to the frequency. 

I don't see anything 'new' in that. It applies to all SMPS, with
suitable changes to the '200 kHz'.

>These out-of-band emissions result in overloading the 
>front-end of a Spectrum Analyser that consequently requires either a 
>pre-selector or calibrated filter to function correctly. There is, of 
>course, the alternative of purchasing a new receiver!

This overloading has been around for a very long time. It is one of the
disadvantages of using a spectrum analyser instead of a CISPR receiver.
-- 
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: VG95373 - advice needed

[John Woodgate]

I read in !emc-pstc that Hudson, Alan  wrote (in
)
about 'VG95373 - advice needed' on Tue, 27 May 2003:
>(I
>suppose I'm asking that if a cabinet meets VG95373 will it pass the EN
>standard equivalent(s) and I can just say so in my Technical Construction
>file)

I suspect that it is irrelevant for the TCF. The conformity applies to
the cabinet before you have pierced any holes in it, or modified it in
any way. There is absolutely no guarantee that the modified cabinet
still meets the requirements of the VG. The same applies to the EN. I
don't know how much consistency there is between the VG and the EN.

The EN standard is: 
Pub Id : BS EN 61000-5-7:2001 
 
Status : Current  
 
Title : Electromagnetic compatibility (EMC). Installation and mitigation
guidelines. Installation and mitigation guidelines. Degrees of
protection by enclosures against electromagnetic disturbances (EM code) 
 
Int Relationships : EN 61000-5-7:2001 IDT; IEC 61000-5-7:2001 IDT 
 
ICS Classification : 33.100.10 
 
Committee Ref : GEL/210;GEL/210/12 
 
ISBN : 0 580 38031 9 
 
Form : A4 
 
Pages : 30 
 
Price : £70.00 Non-member Price 

-- 
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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Harmonics and conducted emissions

[Neil Helsby]

Has anyone else noticed the tendency of modern switch mode power supply 
designers to save manufacturing costs at the expense of harmonic and 
conducted emissions measurements?

EN 61000-3-2:2000 has introduced the concept of Partial Odd Harmonics for the
21st and above. While this adds extra functions to the spread-sheet 
results check, I wonder if it also has an unhelpful side effect.

With conducted emissions, new power supply designs generate peak 
emissions at frequencies below 200 KHz that increase in level inversely 
to the frequency. These out-of-band emissions result in overloading the 
front-end of a Spectrum Analyser that consequently requires either a 
pre-selector or calibrated filter to function correctly. There is, of 
course, the alternative of purchasing a new receiver!

Neil Helsby


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SV: VG95373 - advice needed

[Helge Knudsen]

Hello Alan,

There is no EN standard covering the same subject as this German Military
standard, full title:

VG 95373-15, "Electromagnetic Compatibility-Electromagnetic Compatibility of
Equipment-Part 15: Test Method for Coupling and Screening," Germany,
February 1997.

VG 95373 Part 15. This German military standard describes the shielding
effectiveness of enclosures. The standard covers the frequency range above
30 MHz; between the frequency range of 30 and 200 MHz, a minimum
antenna-to-enclosure separation distance of 2.5 m is specified. This
distance can be reduced to 1 m for frequencies greater than 200 MHz. The
test method specifies that a receiving antenna-which must be small compared
with the enclosure under test-be built into the enclosure for the test.
Although there are technical problems with this standard, it is currently
the only standard applicable to small- and medium-sized enclosures. It is
not surprising that the test method described in VG 95373 Part 15 (or
variations of it) is used for shielding-effectiveness evaluation of small-
and medium-sized enclosures and is favored by manufacturers of conductive
plastic enclosures

You may more information on the subject on:
http://www.ce-mag.com/archive/01/Spring/Ogunsola.html

Best regards

Helge Knudsen
Test & Approval manager
Niros Telecommunication
Hirsemarken 5
DK-3520 Farum
Denmark
Tel +45 44 34 22 51
Fax +45 44 99 28 08
email h.knud...@niros.com




Fra: Hudson, Alan [mailto:alan.hud...@amsjv.com]
Sendt: 27. maj 2003 10:00
Til: EMC-pstc (E-mail)
Emne: VG95373 - advice needed





G'Day!

Does anyone in this collective have working knowledge of a German defence
standard - VG95373 Part 15?

I'm been offered a cabinet which, for EMC matters, the manufacturer states
"meets VG95373 part 15". I don't really want to buy a standard (and spend
hours studying it) for the sake of a one-time buy of one cabinet - does
anyone here happen to know how well VG95373 part 15 compares with the
"usual" EN standards applied for complying with Europes EMC Directive? (I
suppose I'm asking that if a cabinet meets VG95373 will it pass the EN
standard equivalent(s) and I can just say so in my Technical Construction
file)

Regards,

Alan
-- 
Experience: the wonderful knowledge that enables you to recognize a mistake
when you make it again.


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VG95373 - advice needed

[Hudson, Alan]

G'Day!

Does anyone in this collective have working knowledge of a German defence
standard - VG95373 Part 15?

I'm been offered a cabinet which, for EMC matters, the manufacturer states
"meets VG95373 part 15". I don't really want to buy a standard (and spend
hours studying it) for the sake of a one-time buy of one cabinet - does
anyone here happen to know how well VG95373 part 15 compares with the
"usual" EN standards applied for complying with Europes EMC Directive? (I
suppose I'm asking that if a cabinet meets VG95373 will it pass the EN
standard equivalent(s) and I can just say so in my Technical Construction
file)

Regards,

Alan
-- 
Experience: the wonderful knowledge that enables you to recognize a mistake
when you make it again.


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Re: Bad Fuse vs. Good Fuse

[John Woodgate]

I read in !emc-pstc that richhug...@aol.com wrote (in <095A00F3.5FF82361
.0ba45...@aol.com>) about 'Bad Fuse vs. Good Fuse' on Mon, 26 May 2003:
>It could
>be that the faulty components that John Woodgate mentioned fall into this
>category.

The epidemic failures were undoubtedly due to manufacturing defects, not
counterfeiting - unless the manufacturer was shipping the counterfeits
to us! We weren't buying from distributors.
-- 
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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