Re: Electrolytic Capacitors in Primary Circuits
In message web-141102...@california.com, dated Mon, 19 Mar 2007, Robert A. Macy m...@california.com writes: This question is not meant to sound argumentative, but really is a sincere question. Your other two points are spot on, therefore I assume this point is also. but I did not understand it. What do you mean ...failure of industry to support standards terminology...? IEC has a terminology committee, TC1, which shows how important the founders of IEC rated the subject. But over the last two decades, as the 'old timers' who were members of the supporting Working Groups affiliated to the product committees retired (some well into their eighties) to the Great Plenary Meeting in the Sky, they have not been replaced, in spite of repeated pleas. As a result, many of these WGs have had to be disbanded, and TC1 is thus deprived of a large amount of input from specialists in particular subjects. and what would it take to change that? A miracle? Well, making available people who are allowed to devote enough time to the job, who are good at precise language without being overly pedantic, preferably know English and French (German, Spanish and/or Russian would be bonuses) and, above all, are not assigned the task because they are too unpredictable to be allowed anywhere near product development. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: Electrolytic Capacitors in Primary Circuits
This question is not meant to sound argumentative, but really is a sincere question. Your other two points are spot on, therefore I assume this point is also. but I did not understand it. What do you mean ...failure of industry to support standards terminology...? and what would it take to change that? Robert On Mon, 19 Mar 2007 16:51:31 + John Woodgate j...@jmwa.demon.co.uk wrote: In message Not by any means, and the time pressure now applied by the top managements of standard bodies, the failure of industry to support standards terminology and editorial work and the increasing number of standards writers who were never taught English properly are combining to make the situation rapidly deteriorate. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: Electrolytic Capacitors in Primary Circuits
In message be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp, dated Mon, 19 Mar 2007, Tarver, Peter peter.tar...@sanmina-sci.com writes: We've been on the same page all along, John. My approach to Jody's post has been to look at what the standard says and let any failure of logic or design sense fall out from the readers' thoughts. Indeed. I just wanted to spell it out in all its horror for those not easily convinced! That's the way the standard is written. Having been involved in standards writing as long as you have, I'm sure this isn't the first failure of logic you've seen in the process. Not by any means, and the time pressure now applied by the top managements of standard bodies, the failure of industry to support standards terminology and editorial work and the increasing number of standards writers who were never taught English properly are combining to make the situation rapidly deteriorate. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
From: don_borow...@selinc.com Sent: Monday, March 19, 2007 9:02 AM If the power supply in question has a bridge rectifier connected to the mains of a power system with hot and neutral conductors, neither side of the capacitor on the DC side of the bridge can be connected to earth -- there would be a connection from hot to earth every half-cycle through the bridge rectifier. As stated moments ago in another post, my approach to Jody's post has been to look at what the standard says and let any failure of logic or design sense fall out from the readers' thoughts. Regards, Peter L. Tarver, PE ptar...@ieee.org CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina-SCI Corporation (or any of its subsidiaries), or any other person or entity. _ Scanned by Sanmina-SCI eShield ___ _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: Electrolytic Capacitors in Primary Circuits
In message be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp, dated Mon, 19 Mar 2007, Tarver, Peter peter.tar...@sanmina-sci.com writes: If the post-rectifier filter capacitor had one terminal tied to earth, it would need to comply with Y1, Y2 or Y4 requirements, regardless of surges being impedance limited. In that case, it could not be an electrolytic capacitor. A 470 uF 375 V Y-class capacitor would be very large and costly. In THAT case, I don't suppose anyone would ever do it! -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
From: John Woodgate Sent: Friday, March 16, 2007 1:23 PM Tarver, Peter writes: §1.5.6 looks at X and Y capacitors, and those connected between the primary circuit and earth. The cathode of the electrolytic capacitor might not connect to earth, unless the bottom end of the rectifier is earthed. If it doesn't connect to earth, no exception is needed. I thin a little clarification is necessary. Between the mains conductors and the filter capacitor are, typically, a fuse, a common-mode choke, a rectifier diode or a bridge rectifier and a resistor to limit inrush current. In no case that I can envisage is the filter capacitor connected to both mains conductors. In fact, that would probably cause it to explode. If the post-rectifier filter capacitor had one terminal tied to earth, it would need to comply with Y1, Y2 or Y4 requirements, regardless of surges being impedance limited. In 60950-1, §1.5.6, the term, primary, is used throughout. Mains, is not used. The concept of, direct connection, though not explicitly stated, is found in the use of the term, line conductor. Line conductor, is not defined in 60950-1 (though it's used in more than just §1.5.6) and it may be a failing in the standard to not define that term or to not include the term, direct connection. (Inference of the meaning of line conductor might be taken from §1.2.1.1, but that's not very rigorous.) All that aside, Jody's concern that someone was misreading the requirements in §1.5.6 for the post-rectifier filter capacitor is well founded, unless one side of the capacitor is earthed (I've never seen this in an SMPS, but that doesn't mean someone hasn't designed one that way). I suspect the experience level of the engineer Jody's working with is on the low end of the scale. I have seen post-rectifier primary circuits in SMPSs connected to earth by small disk capacitors that I doubt were Y capacitors and the voltages across them were only a few Volts. Moving further and further away from the ac mains in the primary circuit would limit surges currents to almost negligible levels, but §1.5.6 still requires such capacitors meet Y capacitor requirements. Maybe the SMPS manufacturers should lobby TC108, MT2, to make more than one clarification. Regards, Peter L. Tarver, PE ptar...@ieee.org CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina-SCI Corporation (or any of its subsidiaries), or any other person or entity. _ Scanned by Sanmina-SCI eShield ___ _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: Electrolytic Capacitors in Primary Circuits
In message b11802460b4f4b4e963b51adf2fae08b04c4a...@usmafrexmb02.bose.com, dated Mon, 19 Mar 2007, Tyra, John john_t...@bose.com writes: Seems pretty clear to me but, since these are not legal modifications to the standard(s) in questions, it depends on the Agency you are dealing with as to whether they are willing to accept these decisions. OSM interpretations are valid in Europe unless, in a particular case, a test house can give valid reason(s) to reject it. And many are adopted by CENELEC as official interpretations by CENELEC TC108. However, this particular interpretation can be a bit misleading insofar as it concentrates on reasoning related to overvoltage (installation categories) rather than to single-fault input current, which is what the agency may have in mind. The agency in question should take into account that every power supply made has an electrolytic capacitor after the rectifier and there are no safety-related 'approvals' for these capacitors when subjected to alternating supply. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
Here is what the last OSM decisions I have state for both 60950 and 60065 for caps after a rectifier: Capacitors which are connected after a rectifier in a primary circuit of a switch mode power supply unit need not be separately approved. In a primary circuit before a rectifier there is installation category III for Permanently Connected equipment, therefore class X1 capacitors must be used. In a primary circuit before a rectifier there is installation category II for Pluggable equipment Type A and Pluggable equipment Type B, therefore minimum class X2 capacitors must be used. The use of a mains fuse, a mains filter or a varistor cannot be a method to reduce installation category. Secondary circuits are normally in installation category I when the primary is in installation category II. However, a floating secondary shall be subject to the requirements for primary circuit in table III unless separated from primary circuits by an earthed metal screen. Seems pretty clear to me but, since these are not legal modifications to the standard(s) in questions, it depends on the Agency you are dealing with as to whether they are willing to accept these decisions. I agree it would be better to have the standard amended for clarification or an official interpretation from TC108 but when you are in the middle of an Agency submittal there is not usually time for this so hopefully the Agency in question will consider the OSM decision and change their interpretation favorably... From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of John Woodgate Sent: Monday, March 19, 2007 9:35 AM To: emc-p...@ieee.org Subject: Re: Electrolytic Capacitors in Primary Circuits In message b11802460b4f4b4e963b51adf2fae08b04c4a...@usmafrexmb02.bose.com, dated Mon, 19 Mar 2007, Tyra, John john_t...@bose.com writes: I have a copy of the CENELEC Committee OSM decisions for the IEC60065 standard 6th/ 7th editions where the various CENELEC member Agencies agreed that capacitors after a bridge rectifier in a SMPS do not need to be approved. This would be in clause 14.2. I have a meeting in a few minutes but will e-mail you a copy after the meeting. Even so, I think that this matter is formally unclear in the context of IEC/EN 60950 and action is needed to either amend the standard or have an official interpretation issued by IEC TC108, not CENELEC. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: Electrolytic Capacitors in Primary Circuits
In message b11802460b4f4b4e963b51adf2fae08b04c4a...@usmafrexmb02.bose.com, dated Mon, 19 Mar 2007, Tyra, John john_t...@bose.com writes: I have a copy of the CENELEC Committee OSM decisions for the IEC60065 standard 6th/ 7th editions where the various CENELEC member Agencies agreed that capacitors after a bridge rectifier in a SMPS do not need to be approved. This would be in clause 14.2. I have a meeting in a few minutes but will e-mail you a copy after the meeting. Even so, I think that this matter is formally unclear in the context of IEC/EN 60950 and action is needed to either amend the standard or have an official interpretation issued by IEC TC108, not CENELEC. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: Electrolytic Capacitors in Primary Circuits
In message 768ee6ab7d56d54bb5000ec2dd113e71016be...@de01exm61.ds.mot.com, dated Mon, 19 Mar 2007, Leber Jody-G19980 jody.le...@motorola.com writes: I am having trouble convincing an agency that the other side of the rectifier is not between line conductors. Are you or is anyone else on the list aware of any actual documents that state this more explicitly, provided everyone else agrees with this analysis. Look at definition 1.2.8.3. Unfortunately, IEC 60950-1 doesn't define 'directly connected', but the examples indicate what is meant. IEC 60065 does define 'directly connected', in 2.4.3. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
Hello Jody,
I have a copy of the CENELEC Committee OSM decisions for the IEC60065
standard 6th/ 7th editions where the various CENELEC member Agencies
agreed that capacitors after a bridge rectifier in a SMPS do not need to
be approved. This would be in clause 14.2. I have a meeting in a few
minutes but will e-mail you a copy after the meeting.
Regards,
John
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Leber
Jody-G19980
Sent: Monday, March 19, 2007 8:48 AM
To: pat.law...@slpower.com
Cc: emc-p...@ieee.org
Subject: RE: Electrolytic Capacitors in Primary Circuits
Pat,
I am having trouble convincing an agency that the other side of the
rectifier is not between line conductors. Are you or is anyone else
on the list aware of any actual documents that state this more
explicitly, provided everyone else agrees with this analysis.
Jody
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of
pat.law...@slpower.com
Sent: Friday, March 16, 2007 4:29 PM
To: emc-p...@ieee.org
Subject: Re: Electrolytic Capacitors in Primary Circuits
Hi Jody:
UL 60950-1 1st Ed., clause 1.5.6 ('Capacitors in primary circuits')
says:
'A capacitor connected between two line conductors of the PRIMARY
CIRCUIT, or between one line conductor and the neutral conductor, shall
comply with IEC 60384-14:1993, subclass X1 or X2.'
The electrolytic capacitor you mentioned is connected between the
rectifier '+' and '-', not between line conductors.
I always though it interesting that a 0.1uF film cap connected across
the line conductors going into a rectifier had to be safety-rated. But
if you move it to the output side of the rectifier, there's no safety
rating required.
Pat Lawler
SL Power Electronics Corp.
emc-p...@ieee.org wrote on 03/16/2007 11:38:25 AM:
The electrolytic capacitor that sits between the rectifier and
transformer in SMPS is typically not an agency approved component.
Where is this exemption documented in 60950-1, Clause 1.5.6?
Best Regards,
Jody Leber
Senior Regulatory Engineer
jody.le...@motorola.com http://www.motorola.com/producttesting
Motorola Product Testing Services
1700 Belle Meade Court
Lawrenceville, GA 30043
770.338.3581 P
404.387.1224 C
847.761.3145 F
-
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RE: Electrolytic Capacitors in Primary Circuits
Pat,
I am having trouble convincing an agency that the other side of the
rectifier is not between line conductors. Are you or is anyone else
on the list aware of any actual documents that state this more
explicitly, provided everyone else agrees with this analysis.
Jody
From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of
pat.law...@slpower.com
Sent: Friday, March 16, 2007 4:29 PM
To: emc-p...@ieee.org
Subject: Re: Electrolytic Capacitors in Primary Circuits
Hi Jody:
UL 60950-1 1st Ed., clause 1.5.6 ('Capacitors in primary circuits')
says:
'A capacitor connected between two line conductors of the PRIMARY
CIRCUIT, or between one line conductor and the neutral conductor, shall
comply with IEC 60384-14:1993, subclass X1 or X2.'
The electrolytic capacitor you mentioned is connected between the
rectifier '+' and '-', not between line conductors.
I always though it interesting that a 0.1uF film cap connected across
the line conductors going into a rectifier had to be safety-rated. But
if you move it to the output side of the rectifier, there's no safety
rating required.
Pat Lawler
SL Power Electronics Corp.
emc-p...@ieee.org wrote on 03/16/2007 11:38:25 AM:
The electrolytic capacitor that sits between the rectifier and
transformer in SMPS is typically not an agency approved component.
Where is this exemption documented in 60950-1, Clause 1.5.6?
Best Regards,
Jody Leber
Senior Regulatory Engineer
jody.le...@motorola.com
http://www.motorola.com/producttesting
Motorola Product Testing Services
1700 Belle Meade Court
Lawrenceville, GA 30043
770.338.3581 P
404.387.1224 C
847.761.3145 F
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Re: Electrolytic Capacitors in Primary Circuits
A few clarifications: 1. I will agree with Ted that many diode packages will fuse (sometimes explosively... I once had a diode embed itself in my safety glasses) but always as a secondary failure. In other words the diode shorted first and started passing AC. Then the electrolytic looked like a short and then things start popping. 2. In any switching power circuit the EMI filter will be the controlling current limiter. The inductance in the filter reacts to the leading edge of any surge, limiting current and in many cases opening up before the fuse, or any other component, can react. Fred Townsend DC to Light ted.eck...@apcc.com wrote: In regard to Fred Townsend's comment: I am aware that diodes will normally fail shorted. However, even in this state, they provide some current limiting. The internal construction can only pass a given amount of current before the diode will open. I have, however, seen a few poorly designed circuits where there was no fuse on the input. The available fault current was high enough that after the diode shorted out from the overcurrent, it suffered from thermal damage and became an open circuit. Even when the diode fails shorted, there is some resistance as noted which will provide at least some current limiting. In regards to Robert Johnson's comments: I work in an industry where we have numerous field wired ITE products. I have products that are on a 50 A branch circuit. The available fault current can be very high. The selection of fuse for the switch-mode power supply is critical. Even with a common mode choke providing some protection, I have seen fault currents over 200 A when there is a component short after the diode bridge. Some of the small, circuit board mounted fuses have an AIC rating of only 50 A and they do not fail gracefully under worse conditions. I agree that most ITE will not be exposed to high fault currents, but this is not always the case. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC, MGE or Schneider Electric. The speaker does not represent APC's, MGE's or Schneider Electric's official position on any matter. Fred Townsend mailto:f...@dctolight.net fred@dctolight.n etTo Sent by: ted.eck...@apcc.com emc-p...@ieee.org cc emc-p...@ieee.org Subject 03/17/2007 01:55 Re: Electrolytic Capacitors in AMPrimary Circuits See comments below. ted.eck...@apcc.com wrote: I have to agree with Mr. Woodgate that the components between the capacitor and the AC mains make a difference. The available fault current on the AC mains can be very high. It may be 1 kA, 10 kA or even more. A component failure due to a short circuit can be very dramatic. The rectifier alone will likely limit the fault current. If nothing else, the diodes will act as fuses. You could design a rectifier circuit that would allow a high fault current, but you would have to set out to do so and you would spend a lot of money in the process. Ted: I have seen literally thousands of diode failures, mostly from lightning damage. I have never seen a silicon power diode fuse (open). They always fail shorted at about two ohms. When they fail the surge limiting resistor becomes very important. That's where they sometimes use 'fusible resistors'. Shorted diodes often cause secondary failures instead of protecting anything. Fred Townsend DC to Light Besides, proper abnormal condition testing will involve simulating a short circuit on the electrolytic capacitor. The purpose of the test is to verify that the system fails gracefully when
Re: Electrolytic Capacitors in Primary Circuits
In regard to Fred Townsend's comment: I am aware that diodes will normally fail shorted. However, even in this state, they provide some current limiting. The internal construction can only pass a given amount of current before the diode will open. I have, however, seen a few poorly designed circuits where there was no fuse on the input. The available fault current was high enough that after the diode shorted out from the overcurrent, it suffered from thermal damage and became an open circuit. Even when the diode fails shorted, there is some resistance as noted which will provide at least some current limiting. In regards to Robert Johnson's comments: I work in an industry where we have numerous field wired ITE products. I have products that are on a 50 A branch circuit. The available fault current can be very high. The selection of fuse for the switch-mode power supply is critical. Even with a common mode choke providing some protection, I have seen fault currents over 200 A when there is a component short after the diode bridge. Some of the small, circuit board mounted fuses have an AIC rating of only 50 A and they do not fail gracefully under worse conditions. I agree that most ITE will not be exposed to high fault currents, but this is not always the case. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC, MGE or Schneider Electric. The speaker does not represent APC's, MGE's or Schneider Electric's official position on any matter. Fred Townsend fred@dctolight.n etTo Sent by: ted.eck...@apcc.com emc-p...@ieee.org cc emc-p...@ieee.org Subject 03/17/2007 01:55 Re: Electrolytic Capacitors in AMPrimary Circuits See comments below. ted.eck...@apcc.com wrote: I have to agree with Mr. Woodgate that the components between the capacitor and the AC mains make a difference. The available fault current on the AC mains can be very high. It may be 1 kA, 10 kA or even more. A component failure due to a short circuit can be very dramatic. The rectifier alone will likely limit the fault current. If nothing else, the diodes will act as fuses. You could design a rectifier circuit that would allow a high fault current, but you would have to set out to do so and you would spend a lot of money in the process. Ted: I have seen literally thousands of diode failures, mostly from lightning damage. I have never seen a silicon power diode fuse (open). They always fail shorted at about two ohms. When they fail the surge limiting resistor becomes very important. That's where they sometimes use 'fusible resistors'. Shorted diodes often cause secondary failures instead of protecting anything. Fred Townsend DC to Light Besides, proper abnormal condition testing will involve simulating a short circuit on the electrolytic capacitor. The purpose of the test is to verify that the system fails gracefully when the capacitor shorts out. You can't easily do this test on a capacitor directly across the line. The results of shorting out the X-capacitor are heavily dependent on the supply circuit. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC, MGE or Schneider Electric. The speaker does not represent APC's, MGE's or Schneider Electric's official position on any matter. John Woodgate jmw@jmwa.demon.c o.uk
Re: Electrolytic Capacitors in Primary Circuits
The most dependable limiting factor in short circuit currents is usually the power cord. A six foot 16 AWG cord on a 120 volt source will only allow 2500 amps and most branch circuit impedances will lower that further to 1000 amps. Not that these are small numbers. They can cause a lot of damage, but they are nowhere near the 10 kA the branch circuit breakers are expected to limit to. Bob Johnson ITE Safety http://www.itesafety.com ted.eck...@apcc.com wrote: I have to agree with Mr. Woodgate that the components between the capacitor and the AC mains make a difference. The available fault current on the AC mains can be very high. It may be 1 kA, 10 kA or even more. A component failure due to a short circuit can be very dramatic. The rectifier alone will likely limit the fault current. If nothing else, the diodes will act as fuses. You could design a rectifier circuit that would allow a high fault current, but you would have to set out to do so and you would spend a lot of money in the process. Besides, proper abnormal condition testing will involve simulating a short circuit on the electrolytic capacitor. The purpose of the test is to verify that the system fails gracefully when the capacitor shorts out. You can't easily do this test on a capacitor directly across the line. The results of shorting out the X-capacitor are heavily dependent on the supply circuit. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC, MGE or Schneider Electric. The speaker does not represent APC's, MGE's or Schneider Electric's official position on any matter. John Woodgate mailto:j...@jmwa.demon.co.uk jmw@jmwa.demon.c o.uk To Sent by: emc-p...@ieee.org emc-p...@ieee.org cc Subject 03/16/2007 03:23 Re: Electrolytic Capacitors in PMPrimary Circuits In message mailto:be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp, dated Fri, 16 Mar 2007, Tarver, Peter mailto:peter.tar...@sanmina-sci.com peter.tar...@sanmina-sci.com writes: §1.5.6 looks at X and Y capacitors, and those connected between the primary circuit and earth. The cathode of the electrolytic capacitor might not connect to earth, unless the bottom end of the rectifier is earthed. If it doesn't connect to earth, no exception is needed. I thin a little clarification is necessary. Between the mains conductors and the filter capacitor are, typically, a fuse, a common-mode choke, a rectifier diode or a bridge rectifier and a resistor to limit inrush current. In no case that I can envisage is the filter capacitor connected to both mains conductors. In fact, that would probably cause it to explode. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from
Re: Electrolytic Capacitors in Primary Circuits
See comments below. ted.eck...@apcc.com wrote: I have to agree with Mr. Woodgate that the components between the capacitor and the AC mains make a difference. The available fault current on the AC mains can be very high. It may be 1 kA, 10 kA or even more. A component failure due to a short circuit can be very dramatic. The rectifier alone will likely limit the fault current. If nothing else, the diodes will act as fuses. You could design a rectifier circuit that would allow a high fault current, but you would have to set out to do so and you would spend a lot of money in the process. Ted: I have seen literally thousands of diode failures, mostly from lightning damage. I have never seen a silicon power diode fuse (open). They always fail shorted at about two ohms. When they fail the surge limiting resistor becomes very important. That's where they sometimes use 'fusible resistors'. Shorted diodes often cause secondary failures instead of protecting anything. Fred Townsend DC to Light Besides, proper abnormal condition testing will involve simulating a short circuit on the electrolytic capacitor. The purpose of the test is to verify that the system fails gracefully when the capacitor shorts out. You can't easily do this test on a capacitor directly across the line. The results of shorting out the X-capacitor are heavily dependent on the supply circuit. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC, MGE or Schneider Electric. The speaker does not represent APC's, MGE's or Schneider Electric's official position on any matter. John Woodgate mailto:j...@jmwa.demon.co.uk jmw@jmwa.demon.c o.uk To Sent by: emc-p...@ieee.org emc-p...@ieee.org cc Subject 03/16/2007 03:23 Re: Electrolytic Capacitors in PMPrimary Circuits In message mailto:be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp, dated Fri, 16 Mar 2007, Tarver, Peter mailto:peter.tar...@sanmina-sci.com peter.tar...@sanmina-sci.com writes: §1.5.6 looks at X and Y capacitors, and those connected between the primary circuit and earth. The cathode of the electrolytic capacitor might not connect to earth, unless the bottom end of the rectifier is earthed. If it doesn't connect to earth, no exception is needed. I thin a little clarification is necessary. Between the mains conductors and the filter capacitor are, typically, a fuse, a common-mode choke, a rectifier diode or a bridge rectifier and a resistor to limit inrush current. In no case that I can envisage is the filter capacitor connected to both mains conductors. In fact, that would probably cause it to explode. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from
Re: Electrolytic Capacitors in Primary Circuits
I have to agree with Mr. Woodgate that the components between the capacitor and the AC mains make a difference. The available fault current on the AC mains can be very high. It may be 1 kA, 10 kA or even more. A component failure due to a short circuit can be very dramatic. The rectifier alone will likely limit the fault current. If nothing else, the diodes will act as fuses. You could design a rectifier circuit that would allow a high fault current, but you would have to set out to do so and you would spend a lot of money in the process. Besides, proper abnormal condition testing will involve simulating a short circuit on the electrolytic capacitor. The purpose of the test is to verify that the system fails gracefully when the capacitor shorts out. You can't easily do this test on a capacitor directly across the line. The results of shorting out the X-capacitor are heavily dependent on the supply circuit. Ted Eckert American Power Conversion/MGE http://www.apc.com/ The items contained in this e-mail reflect the personal opinions of the writer and are only provided for the assistance of the reader. The writer is not speaking in an official capacity for APC, MGE or Schneider Electric. The speaker does not represent APC's, MGE's or Schneider Electric's official position on any matter. John Woodgate jmw@jmwa.demon.c o.uk To Sent by: emc-p...@ieee.org emc-p...@ieee.org cc Subject 03/16/2007 03:23 Re: Electrolytic Capacitors in PMPrimary Circuits In message be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp, dated Fri, 16 Mar 2007, Tarver, Peter peter.tar...@sanmina-sci.com writes: §1.5.6 looks at X and Y capacitors, and those connected between the primary circuit and earth. The cathode of the electrolytic capacitor might not connect to earth, unless the bottom end of the rectifier is earthed. If it doesn't connect to earth, no exception is needed. I thin a little clarification is necessary. Between the mains conductors and the filter capacitor are, typically, a fuse, a common-mode choke, a rectifier diode or a bridge rectifier and a resistor to limit inrush current. In no case that I can envisage is the filter capacitor connected to both mains conductors. In fact, that would probably cause it to explode. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Electrolytic Capacitors in Primary Circuits
Hi Jody:
UL 60950-1 1st Ed., clause 1.5.6 ('Capacitors in primary circuits') says:
'A capacitor connected between two line conductors of the PRIMARY CIRCUIT,
or between one line
conductor and the neutral conductor, shall comply with IEC 60384-14:1993,
subclass X1 or X2.'
The electrolytic capacitor you mentioned is connected between the
rectifier '+' and '-', not between line conductors.
I always though it interesting that a 0.1uF film cap connected across the
line conductors going into a rectifier had to be safety-rated. But if you
move it to the output side of the rectifier, there's no safety rating
required.
Pat Lawler
SL Power Electronics Corp.
emc-p...@ieee.org wrote on 03/16/2007 11:38:25 AM:
The electrolytic capacitor that sits between the rectifier and
transformer in SMPS is typically not an agency approved component.
Where is this exemption documented in 60950-1, Clause 1.5.6?
Best Regards,
Jody Leber
Senior Regulatory Engineer
jody.le...@motorola.com
http://www.motorola.com/producttesting
Motorola Product Testing Services
1700 Belle Meade Court
Lawrenceville, GA 30043
770.338.3581 P
404.387.1224 C
847.761.3145 F
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Re: Electrolytic Capacitors in Primary Circuits
In message be3336be85968d49be01e66d6e365b1e01b5a...@sjc1amfpew01.am.sanm.corp, dated Fri, 16 Mar 2007, Tarver, Peter peter.tar...@sanmina-sci.com writes: §1.5.6 looks at X and Y capacitors, and those connected between the primary circuit and earth. The cathode of the electrolytic capacitor might not connect to earth, unless the bottom end of the rectifier is earthed. If it doesn't connect to earth, no exception is needed. I thin a little clarification is necessary. Between the mains conductors and the filter capacitor are, typically, a fuse, a common-mode choke, a rectifier diode or a bridge rectifier and a resistor to limit inrush current. In no case that I can envisage is the filter capacitor connected to both mains conductors. In fact, that would probably cause it to explode. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk There are benefits from being irrational - just ask the square root of 2. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
From: Jody Leber Sent: Friday, March 16, 2007 11:38 AM The electrolytic capacitor that sits between the rectifier and transformer in SMPS is typically not an agency approved component. Where is this exemption documented in 60950-1, Clause 1.5.6? Jody - Sorry about the earlier e-mail. Itchy trigger finger, I guess. §1.5.6 looks at X and Y capacitors, and those connected between the primary circuit and earth. The cathode of the electrolytic capacitor might not connect to earth, unless the bottom end of the rectifier is earthed. If it doesn't connect to earth, no exception is needed. Regards, Peter L. Tarver, PE ptar...@ieee.org CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina-SCI Corporation (or any of its subsidiaries), or any other person or entity. _ Scanned by Sanmina-SCI eShield ___ _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
Pardon me, my response to Jody was sent prematurely. Please disregard it. Peter CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina-SCI Corporation (or any of its subsidiaries), or any other person or entity. _ Scanned by Sanmina-SCI eShield ___ _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
RE: Electrolytic Capacitors in Primary Circuits
From: Leber Jody Sent: Friday, March 16, 2007 11:38 AM The electrolytic capacitor that sits between the rectifier and transformer in SMPS is typically not an agency approved component. Where is this exemption documented in 60950-1, Clause 1.5.6? Which requirement were you referring to for which you think an exemption is needed? Regards, Peter L. Tarver, PE ptar...@ieee.org CONFIDENTIALITY This e-mail message and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail message, you are hereby notified that any dissemination, distribution or copying of this e-mail message, and any attachments thereto, is strictly prohibited. If you have received this e-mail message in error, please immediately notify the sender and permanently delete the original and any copies of this email and any prints thereof. ABSENT AN EXPRESS STATEMENT TO THE CONTRARY HEREINABOVE, THIS E-MAIL IS NOT INTENDED AS A SUBSTITUTE FOR A WRITING. Notwithstanding the Uniform Electronic Transactions Act or the applicability of any other law of similar substance and effect, absent an express statement to the contrary hereinabove, this e-mail message its contents, and any attachments hereto are not intended to represent an offer or acceptance to enter into a contract and are not otherwise intended to bind the sender, Sanmina-SCI Corporation (or any of its subsidiaries), or any other person or entity. _ Scanned by Sanmina-SCI eShield ___ _ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list.Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald:emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
