Hi Kathy:
Someone who seemed to believe such a edict was sent
out resently asked me to check to I asked this group.
Maybe this is just a very bad joke from someone who
really doesn't know what he is asking.
I wouldn't cross off the question this way.
Be aware that there are a
Hi Bob:
A company I represent has a problem with their switching power supply.
A single point failure in the regulator can cause the output voltage to
rise higher than the voltage ratings of the electrolytic capacitors. As
a result, the capacitors are overstressed and fail in a
Posted on behalf of Bobbie Cronquist, John Wright, and
Julie Gaevert.
Some sad news about Joe Wujak, whom many of you may know and remember.
Bobbie Cronquist
- Forwarded message --
I have the very unfortunate task of telling everyone that Joe Wujek
and
Hi Peter:
There are two schools of thought:
1) Clearance is an independent, stand-alone criterion.
2) Clearance determines electric strength of air and is
an alternate means for determining the electric
strength of air.
If you are in the first school, then there is no reason
Hello from San Diego:
What countries and what standards require the indoor use:
symbol?
This symbol is comprised of a stick-figure house with an
arrow pointing from outside to inside.
My experience with this symbol is through TUV Product Service.
They require
Hi Doug:
This subject is NOT in the you got to be kidding me
category.
Many years ago, such a fuel-cell generator was installed
at IBM Kingston and ran for a year as an experiment.
Since this is a SOURCE of electric energy, it falls into
the same category as home wind generators and home
Hi John:
The subject here is regarding the words 'shall' vs. 'must' in various of
product safety standards (including UL 1950 3rd Ed. and EN60950).
Does anyone have any insight into the definitions of these as applicable to
product safety? I have heard there are differences,
Hi George:
Could someone give me an explanation of what makes a power source
Inherently Limited..
Others have provided excellent responses to your question.
Perhaps I can embellish their answers.
A doorbell transformer is the prime example of an inherently
limited power source.
The
Hi George:
Pal is primarily used throughout Europe and NTSC is used in USA, Canada,
Mexico and Japan.
Does anyone know of any other countries that may use NTSC ?
Check out the following web sites:
http://www.bbc.co.uk/aberdeen/eng_info/world_tv_standards.shtml
Posted on behalf of Gary Jong:
--
I'm the Staffing Manager for the Philips Mobile Computing Group (PMCG)
PMCG designs and develops new generations of the award winning Velo
and other mobile computing and communications platforms based on the
Windows CE operating
Hi Tania:
I, too, have had the same inspection experiences (saw a transformer
and prove solder time-temperature).
In the case of the transformer, I offered to take the inspector to
the transformer manufacturing plant to make the measurments during
the manufacturing process.
The
Hi Moshe:
The voltage of the neutral with respect to the ground wire
is a function of its resistance and its current:
E = I * R
Maximum normal current is the rating of the fuse or circuit-
breaker protecting that particular circuit. For a 120-volt
circuit in the USA and Canada, the
Hi Joe:
liability and such. Can anyone share some more info as to their reasons for
listing or not listing such a product which is well below hazardous limits.
There are two schools of thought:
1. Because of its low-voltage supply, the unit is exempt from
most safety
Hi Jim:
1. Am I correct that the North American agencies (CSA, UL, ETL, etc.)
allow line-to-ground MOV's? The standards we work with do not
disallow
them, but this is the sort of issue for which agencies often invoke
desk drawer requirements.
Can't answer this one.
But, why use surge
Hi Rick:
If a product has a 4A rated input current (120V AC), how does one
determine the rating of the in-line Fuse for safety/Fault testing?
There is no relationship between input rating and the fuse
rating.
The input rating is the maximum input under normal operating
conditions.
Hi Allen:
I'll take a shot at this one! (At one time I dealt with high-
fidelity high-frequency signals where the effects of connectors
could be observed in the waveforms.)
The ideal transmission line is terminated at both ends with its
characteristic impedance.
In some circumstances, you
Hi George:
Can anyone point me to a resource (Book, Chart etc) that lists ignition
points for various (flammable) materials ?
Flash-ignition temperatures and self-ignition temperatures for
various generic plastic materials are published in:
International Plastics Flammability
Hi Peter:
The Dielectric Voltage Withstand Table in UL1950/EN 60 950 lists
equipment with Mains DC. What does this mean?
You make it difficult to answer this question because you
used a term that does not appear in UL 1950:
Mains DC
I did an electronic search of the standard for
Hi Lauren:
At the risk of being shown otherwise...
Determining the actual heat dissipation of your product could be very time
consuming. It would involve, in part, knowing the electrical efficiency of
I would argue that, using the law of conservation of
energy, this is not at all time
Hi Scott:
Under the law of the conservation of energy, all of the energy
going into a product must be accounted for.
Energy is measured in joules.
One joule is one watt-second.
One watt is one joule/second.
All of the watts entering the product must be accounted for.
All of the watts are
Hi Jeff:
If a component abnormal test generates excessive and sustained smoke
(several minutes), but does'nt breach reinforced or double insulation, nor
emit flame from the enclosure, is it considered a failure? Intuitively, it
seems like it would be, because of toxicity, but I
Hi Jeff:
I need to clarify my earlier question on conductive paint. We bond our
enclosure panels together with screws. We use external-tooth starwashers
between the screws and sheet metal to achieve a reliable, protective-earth
bond. On our painted panels, we mask the paint so
Hi Jeff:
My company is proposing to use conductive paint on our enclosures, and I
would like your input as to the acceptability of this vis-a-vis protective
earth bonding of enclosure panels. I am interested in the perspective of
both European and North American requirements.
The
Hi George:
Along this line, I was asked, if placing power and ground traces on
separate (PCB) layers would be an acceptable way of reducing clearance
requirements between (gndpwr) traces. Is there anyway to anticipate
clearance between PCB layers of a multi layered board? Is
Hi Ali:
Today I received a call from one of distributors stating that as of August
of this year, Argentina will have their own power cord requirements. I
believe Argentina has the same configuration as Australia. Does anyone know
where I can find out more about this requirement?
Hi John:
In the CB Scheme National Differences document, Danish and Norwegian
requirements (in 6.3.3.1 and 6.2.1.2, respectively) make reference to
equipotential bonding. Can anyone tell me exactly what equipotential bonding
is? I assume that it is some form of grounding...would having a
Hi Doug:
My question is this, is it because the inverter has a low voltage input and
they do not have to comply to a standard like EN61010 or UL1950, or is this
something the manufacturers haven't addressed because no one has ever asked?
I don't think anyone but the manufacturers can
Hi Ray:
I know that at one time, UL had accepted a HAR type cordset. Now, I have
...
...
Does anyone know why UL stepped back away from accepting EU cords?
My guess is:
UL accepts HAR cordage (not cordsets) for products going
to countries where the HAR certification is accepted.
UL
Hi John:
He sees the video distorted and was wondering
about any health risks.
The first thing you should do is ascertain that the
distortion is caused by an external source or an
internal (to the monitor) source. It is possible
that the degauss circuit has failed, in which case
Hi Peter:
I understand the construction to be that of a mains
extension from a wall outlet outside the safe via a
plug to two socket-outlets inside the safe.
Your question is Does the safe now fall under the LVD?
Plugs, mains cordage, and socket-outlets are NOT
included in the LVD as they
Hi Jim:
You ask a number of questions about fire enclosures for
IT equipment.
Section 4.4.5 of UL1950 appears to require a fire enclosure for essentially
anything that contains a printed circuit board assembly
Sub-clause 4.4.5.1 essentially says that all conductors
and components
Hi Frank:
Interesting. During an audit of the facilities of a former employer, the
auditor specifically requested that we didn't use the Simpson 228 for
EN60950 because of the roll-off of the analog movement above 100Hz. The
suggested fix was to build the network as described
Hi Pete:
It seems to me that there are several kinds of conductive
parts that we need to be concerned about from a safety
perspective:
1. Energized parts at hazardous voltage.
2. Energized parts at non-hazardous voltage.
3. Energized parts at non-hazardous current.
4. Grounded/earthed
A meter for IEC 60950 may not be adequate for IEC 61010,
especially if the unit under test has a reasonably high
frequency switch mode power supply.
The high frequencies generated in a switching mode power supply
are negligible in the presence of the mains-frequency leakage
From owner-emc-p...@majordomo.ieee.org Fri Mar 12 02:24:22 PST 1999
Received: from hpsdlo.sdd.hp.com (hpsdlo-sw.sdd.hp.com [15.26.112.11]) by
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Hi Jeff:
Quotes from the 1996 NEC:
110-2. Approval. The conductors and equipment required
or permitted by this Code shall be acceptable only if
approved.
Approved: Acceptable to the authority having jurisdiction.
90-7. Examination of Equipment for Safety. For specific
items of
Most of the stories are stories about EMC fixes.
I've got one that is not and won't be fixed. I
just live with it!
It involves my '96 Honda Accord, bought new.
I'm in San Diego, about 100 miles south of Los
Angeles. I noticed that 50 kW Los Angeles AM
stations such as KFI and KNX were
Hello from San Diego:
I said:
1. For the North America, does a NEMA 125 V, 20 A plug meet the
pluggable B definition?
No. The objective of the Pluggable Type B connection is that
of a reliable, non-defeatable earth connection. The NEMA 20 A
plug uses the same
Hello Peter:
1. For the North America, does a NEMA 125 V, 20 A plug meet the
pluggable B definition?
No. The objective of the Pluggable Type B connection is that
of a reliable, non-defeatable earth connection. The NEMA 20 A
plug uses the same earthing connection as the NEMA 15 A
Hi Moshe:
I need fuses and fuse holders for 10kV line. Can someone tell me who is
making these (or what
are other altenatives to current limiting on high voltage lines)?
10 kV fuses are BIG!
I checked the Littlefuse web site and found a medium voltage
fuse rated 14,400 volts, 0.5
Hi Moshe:
Can someone enlighten me on the status of safety of using LED's as
indicators. Are they still
to be suspected as radiation sources (60825) and what should I do in the
design (?) to prove
them safe?
EN 60950 Amd 11 invokes EN 60825.
EN 60825 applies to ALL lasers
Hi Raymond:
Does anyone know why the standard selects 25A, not others?
The presumption is that a zero-impedance fault occurs
between the live mains and the protective earth/ground
circuit. This means the full current of the mains will
flow in the protective earth/ground circuit until the
As an inactive member of ECMA TC 12, and a TC 12 contributor for the
first year of this work, I am fowarding a message from Bob Griffin,
Compaq, regarding a new product safety standard for electronic
equipment.
Unfortunately, I am unable to include the files Bob describes.
(Apparently, the
Hi Allen:
Does anyone know how to calculate minimum distances between traces on
a printed circuit board that would allow one to pass the dielectric test
at a given voltage? Or has anyone taken any empirical data that would
shed light on this topic? Also, would trace width have an impact
Hi Dan:
Can anyone explain the advantages/disadvantages of going through a notified
body for CE Mark as opposed to self certifying? It costs a load of money to
retain the services of a notified body and I was wondering what you really
get from it.
Its a business decision.
)
id QAA09924; Thu, 7 Jan 1999 16:18:12 -0500 (EST)
From: pe...@itl.co.il (Peter Merguerian)
To: dmck...@corp.auspex.com, Rich Nute ri...@sdd.hp.com
Date: Thu, 7 Jan 1999 23:12:35 +0200
MIME-Version: 1.0
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7BIT
Hi Doug:
Isn't this a variation of using the traces as a fusing element
instead of using a real fuse?
Not necessarily.
In Peter's situation, the test was that of the integrity
of the insulation between the TNV circuit and the other
circuits.
So, if the fused trace did not bridge
Hi Steve:
Check out:
http://www.osha-slc.gov/SLTC/nrtl/index.html
This URL shows all the standards for which UL and
other NTRLs are accepted as NRTL.
That's AMAZING! The URL shows that OSHA accepts
the following UL 3101 certifications:
Certification Accept
house
Hello Arjen:
The definitions for Class 2 and Class 3 circuits may be
found in the USA National Electrical Code, NFPA 70:
Article 725-2 Definitions.
Article 725-41(a) Power sources for Class 2 and
Class 3 circuits.
Figure 725.41
Hello Maria:
Assuming you are seeking to use the CE mark (indicating
compliance to the Low Voltage Directive) on your
product...
Assuming the output of the wall adapter is SELV and
Limited Power (EN 60950)...
Assuming the wall adapter bears the CE mark...
Assuming your product operates
Hi Barry:
But, as far as I know, we cannot do the same way for Australia. The DoC
must be signed by a rep in Australia.
Europe DoC rules are established by the EU.
Australia is not a part of the EU, and is subject to
its own rules.
The DoCs are the same in name only.
But, the EU
Hi Jeff:
Low-power transformers are difficult if not impossible to
protect by means of a primary fuse. As you have pointed
out, the change in current between rated load and short-
circuit reflected to the primary is too small to cause a
fuse to operate.
The safety issue is that of
Hi Scott:
The cause of the neutral-earth voltage is the neutral
current times the neutral resisitance to the point
where the neutral is connected to earth. The higher
the neutral current, the higher the voltage difference
between the neutral and earth conductors.
Building power distribution
Hi Craig:
The short answer to your questions is:
Continue as you are currently doing (i.e., provide
the correct cordset for the country of destination)
HP provides the correct cordset for the country of
destination. (Almost all of our products are wide-
range, 100-240 V, 50-60 Hz.)
Hi Peter:
1. The coaxial cable output is conductively connected to the input.
It carries the same voltage and an amperage of 1 A (limited to 3 A
max). Assuming the input supply tolerance not to exceed 60 Vdc,
does everyone agree that this is SELV?
ELV, yes. SELV, I don't know
Hi Doug:
The picture shows three wires. I assume this is
a DELTA configuration, since a WYE configuration
requires four wires.
I agree with you that most power distribution is
the DELTA configuration.
I suppose one might claim that the fourth conductor
of the WYE is the ground. I would
Hi Glyn:
Two comments:
1) In a power cord, two conductors must be identified, one
being the protective earthing conductor, the other being
the neutral conductor (assuming a polarized connection
to the supply).
Here are the required identification colors according to
Hello Peter and Gary:
We have found the CB Certificate and Test Report effective
for:
CE mark test report.
Eastern bloc countries, especially Poland, Czechia,
Slovakia, Hungary.
China (but requires factory inspection).
Korea.
Singapore.
Japan (when
Hi Peter:
Unless the power supply has a CB Test Report of its own (and
most do not!)
As a matter of course, if we are going for a CB on the
end-product, then we request a power supply CB as a part
of doing business with the power supply vendor/manufacturer.
Power supply safety
Hi Richard:
The manufacturer must keep these
available for the inspectors that appear each quarter.
To my knowledge, no third-party certifier has required
such records.
Most would like you to do so, and if you volunteered,
they would be very happy
Hi Kendall:
I would take a step back and ask how does my company
confirm that the plastic part we ordered meets our specs ?
Does incoming inspection check the cert attached with the
shipment and keep a record that they cross-checked it with
a component specification or
Hi Doug:
Active (as opposed to passive) power factor correction
for electronic products is a high-frequency switching
rectifier (ahead of the switching-mode power supply)
which stores energy in an inductor rather than in a
capacitor.
The current waveform is in phase with the voltage
Hi Peter:
1. Per UL1950/EN60950 can any capacitor be used to bridge basic
insulation between a TNV-3 circuit and a SELV circuit or should it
be a Recognized/Certified Y-capacitor?
No.
By definition, only a Y capacitor is considered basic
insulation. All other capacitors are
Hello from San Diego:
I think the discussion confused two issues:
1) Laser pointer safety.
2) Use of a laser pointer to imitate a laser aimer.
The safety of ALL lasers, including pointers, is
controlled by the US Government, Federal Drug
Administration (FDA). The posted FDA warning
Fire is a very complex phenomeon. It is complex
because ignition requires
* electrical power dissipation,
* component fault temperature exceeding the
fuel material ignition temperarture,
* electrical and thermal energy sufficient
to raise the fuel to ignition
Hi Terry:
You ask a bunch of questions about material use and
flammability ratings for such materials.
Some of the questions ask about applications of the
standards.
Some of the questions ask whether the requirements
truly reduce the possibility or consequences of fire.
1. Does small size
Hi Scott:
There is no requirement that ratings label data be
provided on a single label or in a specific location.
You have already mentioned that specific data must be
located near the device, i.e., input ratings near the
power input, fuse ratings and fuse replacement warning
near the
Hi Peter:
1. Can someone explain a polarized plug.
A polarized plug (and mating socket) is one which
maintains the neutral conductor of the power
source through the socket/plug to the product.
A polarized plug can be either 2-wire or 2-wire
plus grounding. (For the
Hi Peter:
I'm not an expert in UL 508, and have been only
peripherally involved in some product certifications.
So, my comments may not be highly accurate.
As a general rule, UL almost always allows testing
in lieu of constructional requirements. This is
specifically stated in the Foreword
Hello from San Diego:
If there is a portable IT product which bottom surface can become hot
(around 49 C) during use, would you recommend to put a warning label onto
the product or would you consider a warning in the operator's manual as
sufficient ?
Here's an experiment:
Place a
Hi Judd:
A universal battery charger that I am reviewing is powered by AC 110-220 or
24VDC.
The 24 VDC enters the device via a male IEC 320 connectorOUCH!.
The AC enters via a non-detachable recognized power cord with NEMA- 5-15
molded male connector.
Here is the Scope
Hi George:
You can view the IEC 417 symbols at:
http://w3.hike.te.chiba-u.ac.jp/iec417/ver2.0/html/index.html
As for download, the site bears a copyright as does the standard.
Best regards,
Rich
-
This message is coming from the emc-pstc discussion list.
To cancel your
Hello Diaco:
My reading of Clause 6 of IEC 950/EN 60950 is:
between TNV circuit and primary circuit:
double or reinforced insulation, including applicable
creepage distance and clearance, or
basic insulation and a grounded conductive barrier,
including
Hi Chris:
Here's a better URL:
http://scifun.chem.wisc.edu/CHEMWEEK/Ozone/ozone.html
This one answers almost all of your questions!
Best regards,
Rich
-
This message is coming from the emc-pstc discussion list.
To cancel your subscription, send mail to majord...@ieee.org
The IEEE EMC Society has published a call for papers for
the IEEE 1999 International Symposium on Electromagnetic
Compatibility. The following details are taken from the
call for papers. I received the notice this past week.
The EMC Society gives just 3 weeks do submit an abstract!
The
Hello from San Diego:
I would like to encourage my emc-pstc product safety
colleagues to consider presenting a product safety
paper to the IEEE EMC Symposium under TC-8, Safety.
In the field of product safety, we need to improve the
level of both individual professionalism and the product
Hi Ron:
First, for assistance with an NEC issue, you SHOULD contact the
NEC authors, the NFPA. They have the following web site:
http://www.nfpa.org/
Click on:
Proposals /
Comments
Query
Display
Then click on:
Staff Directory
Then click on:
Engineering
Hello from San Diego:
As a general rule, products powered from a (NEC, CEC)
Class 2, (IEC) SELV, or battery power source need
not be certified for safety. The general rule (e.g.,
NEC, LVD, et al) exempts products operating at ELV,
e.g., 50 volts or less.
(As near as I can tell, the NEC
Hi Manning:
Some comments in response to your assertions...
You pose the question: What is the purpose of the
n switch?
The n switch is provided for one of two purposes:
1) To represent a failure (open-circuit) of the
neutral conductor during leakage-current testing.
2) To
Hi Ron:
You pose a tough question that probably has as many answers
as there are jurisdictions in the USA.
Does anyone know if there are any local, county and/or state jurisdictions
that
go beyond, or are in addition to, those regulations of OSHA and/or the NEC?
Here's the URL for
Hi Manning:
A long, long time ago, I discussed this with some UL
folks. I recall that the time this circuit was
developed as BEFORE grounding was implemented in the
USA. So, everything was 2-wire.
UL was testing lots of appliances, especially
refrigerators. The n switch was put in the
Hello from San Diego:
Ron Pickard asks:
... what specific requirements are there that positively
and unequivicably require NRTL Listing...
To my knowledge, there are two, independent sets of regulations
that require third-party safety certification:
1) OSHA (safety of electrical
it as one alternative.
George Alspaugh
Lexmark International
-- Forwarded by George Alspaugh/Lex/Lexmark on 09/16/98
03:13 PM ---
Rich Nute richn%sdd.hp@interlock.lexmark.com on 09/16/98 02:27:03 PM
Please respond to Rich
Hello from San Diego:
There have been a number of interesting points of view
expressed here on the various world safety certification
schemes.
Let's review the various schemes:
1. Third-party certification.
This scheme involves one or more third-party
organizations, one who tests
Hi Gary:
You pose yet another provocative idea! Re-arranging
your statement, I come up with the following:
The requirements in the standards must be made based on
1) the real world situation, and
2) engineering judgement,
3) evaluation, and
4) continued investigation into
Hello from San Diego:
A complete list of CB Scheme NCBs is available at:
http://www.cbscheme.org/cbcntris.htm
The following countries have multiple NCBs:
Germany
VDE
TUV Rheinland
TUV Product Service
India
BIS
STQC
U.K.
Hi Rick:
After going looking at the site Rich Nute provided, I see no reference
to South American countries. Are South America countries part of the CB
scheme as well?
Nope.
And none in Central America.
Only one in Africa.
Only three in Asia (China, Japan, and Singapore).
Only
that the
HAR marking is not mandatory; rather, a color thread can be used to indicate
the agency that has approved the wire. Good luck on the rest.
--
From: Rich Nute[SMTP:ri...@sdd.hp.com]
Reply To: Rich Nute
Sent: Friday, September 11, 1998 1:25 PM
Hello from San Diego:
Two questions about Euro cordage:
1. HAR mark.
I have heard that this mark can only be used when
the cordage is manufactured in a factory physically
located within the HAR countries. Is this true?
Can you cite the HAR regulation?
2. CE mark.
I
Hi Doug:
1) Designed to meet (safety standards list) ...
___ highly acceptable
___ acceptable
___ no opinion
___ unacceptable
comments:
In my experience, this represents wishful thinking on the
part of the party making the statement. Too too many
Hello from San Diego:
Here is a job opportunity I am posting on behalf of the
headhunter.
Best regards,
Rich
-
Richard Nute Product Safety Engineer
Hewlett-Packard Company Product Regulations
Hi Donald:
You ask a whole stack of questions...
Safety certification of a product is done by means of
a contract between the manufacturer (or his representative)
and the certification house. This contract restricts
all data, including the safety report, if any, as private
between the
Hi Scott:
Welcome to the world of jawboning.
Jawboning is the Nixon-era activity of government officials
speaking as if a law was in place governing a specific activity
when, in fact, there was none.
Some engineers and managers from third-party safety certification
organizations practice
Hi Charles:
I have been told that the Russian Authorities
will only accept a CB report from Nemko. Is this true?
I don't believe this is true as this is against the basic
idea of the CB Scheme. A CB Certificate and Test Report
is universal, regardless of the issuing organization.
Hi Gary:
In the USA and Canada, third-party safety certification is
mandated by OSHA, the NEC, and Canadian provincial laws.
There are many third-party certifiers who can provide one
mark acceptable in both countries.
If you were not using a certifier acceptable to both
countries, a CB
Hi Jack:
While your specific question is off the mark of this
discussion group, there is a related issue that is on
the mark for this discussion group...
1) Is there a policy governing activity directed towards
standards and research into standards issues? Does
management condone
Dear Group,
2.4.2 of UL1950 defines the upper current limit for Limited Current Circuits
when the frequency is above 1kHz as 0.7mA multiplied by the frequency in
kilohertz (up to 70mA peak). Since the limit increases (up to
70mA) as the frequency goes up, one can assume
Hi Bob:
Electric shock requires both voltage AND current. Most
safety standards specify conditions for electric shock
when the voltage is 30 volts rms or more AND the current
is either 0.25, 0.5, or 3.5 mA rms or more.
Think of it as an AND gate. Voltage exceeding 30 V rms
AND current
Hi Doug:
Probably the best single reference to non-ionizing
radiation safety is:
http://www.osha-slc.gov/SLTC/RadiofrequencyRadiation/index.html
Best regards,
Rich
-
Richard Nute Quality Department
Hi Doug:
For reliable safety data on non-ionizing radiation,
check out the following web pages:
1. http://homepage.seas.upenn.edu/~kfoster/comar.htm
This is the IEEE Committee on Man and Radiation, COMAR.
Probably has the most reliable information on body
susceptibility to
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