RE: Ground Fault Circuit Interrupter tripping
Hi Brian: First, you should measure the current in the ground wire with an oscilloscope and a current probe or measure the voltage across a low-value resistance such as 10 ohms in series with the ground wire. Second, you should measure the current in the ground wire with a RMS ammeter. These should confirm that the difference current is tripping the GFCI. If the high frequency is what is causing the GFCI to trip, you might want to consider re-designing the EMC filter to lower the high-frequency currents in the ground wire. An ideal EMC filter should return the currents generated in the power supply to the power supply, not via the mains circuits. The worst-case fix is to use a 1:1 isolation transformer between the mains and your equipment. Make the measurements so that you know what is causing the GFCI to trip. Best regards, Rich -Original Message- From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: Monday, August 20, 2007 6:50 AM To: ri...@ieee.org; emc-p...@ieee.org Subject: RE: Ground Fault Circuit Interrupter tripping Thanks for the great information. Let me see if I'm comprehending it correctly. - A product can pass the leakage current test and not pose a hazard to the user but still trip a GFCI. In such cases, is there an alternative to the GFCI? If the NEC requires a GFCI in a location but a device used in that location falsely trips the GFCI, can you wire the instrument without the GFCI and still meet the NEC requirements? (are their exclusions?). Is there something you can do, such as provide an addition safety earth ground connection, instead of the GFCI? If I'm correctly understanding the reason our product is tripping the GFCI, there is nothing we can do about it. So, our only choice is to find an exclusion or an alternate to the GFCI that would satify everyone. Any suggestions would be appreciated. The Other Brian -Original Message- From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of rn...@san.rr.com Sent: Friday, August 17, 2007 2:17 PM To: emc-p...@ieee.org Subject: RE: Ground Fault Circuit Interrupter tripping Hello John: I've never measured the 'frequency response' (trip current vs. frequency) of a GFCI (they don't occur in UK, we have RCCBs) but I suspect that the trip current is higher than the design value at higher frequencies. As far as I know, there is no frequency compensation in the GFCI. The frequency response is determined by the core characteristics and the IC amplifier characteristics. Virtually all US/Canada GFCIs use the National Semiconductor LM1851 IC. The data sheet includes some good information on GFCI circuits and circuit performance. There are no frequency response specs that I could find. Here is the URL for the LM1851 and data sheet: http://www.national.com/mpf/LM/LM1851.html Here is another web site for GFCI information: http://www.codecheck.com/gfci_principal.htm The original question pointed out that the leakage current was in spec, but the load nevertheless tripped the GFCI. The only conclusion is that the leakage current meter and the GFCI do not have the same measuring circuits -- which they don't. We do know that the leakage current measuring network accounts for the response of the body to frequency, while the GFCI has no such metering circuit network. Best regards, Rich Richard Nute Product Safety Consultant San Diego - 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: Ground Fault Circuit Interrupter tripping
Thanks for the great information. Let me see if I'm comprehending it correctly. - A product can pass the leakage current test and not pose a hazard to the user but still trip a GFCI. In such cases, is there an alternative to the GFCI? If the NEC requires a GFCI in a location but a device used in that location falsely trips the GFCI, can you wire the instrument without the GFCI and still meet the NEC requirements? (are their exclusions?). Is there something you can do, such as provide an addition safety earth ground connection, instead of the GFCI? If I'm correctly understanding the reason our product is tripping the GFCI, there is nothing we can do about it. So, our only choice is to find an exclusion or an alternate to the GFCI that would satify everyone. Any suggestions would be appreciated. The Other Brian From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of rn...@san.rr.com Sent: Friday, August 17, 2007 2:17 PM To: emc-p...@ieee.org Subject: RE: Ground Fault Circuit Interrupter tripping Hello John: I've never measured the 'frequency response' (trip current vs. frequency) of a GFCI (they don't occur in UK, we have RCCBs) but I suspect that the trip current is higher than the design value at higher frequencies. As far as I know, there is no frequency compensation in the GFCI. The frequency response is determined by the core characteristics and the IC amplifier characteristics. Virtually all US/Canada GFCIs use the National Semiconductor LM1851 IC. The data sheet includes some good information on GFCI circuits and circuit performance. There are no frequency response specs that I could find. Here is the URL for the LM1851 and data sheet: http://www.national.com/mpf/LM/LM1851.html Here is another web site for GFCI information: http://www.codecheck.com/gfci_principal.htm The original question pointed out that the leakage current was in spec, but the load nevertheless tripped the GFCI. The only conclusion is that the leakage current meter and the GFCI do not have the same measuring circuits -- which they don't. We do know that the leakage current measuring network accounts for the response of the body to frequency, while the GFCI has no such metering circuit network. Best regards, Rich Richard Nute Product Safety Consultant San Diego - 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 LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - 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 __
A book for China RoHS
To Those Who are Interested in: The China Quality Management Association for Electronics Industry (CQAE) published a book in regard to the China RoHS. The news is available at http://www.cqae.com/zxdt-xw.asp?column_id=978 http://www.cqae.com/zxdt-xw.asp?column_id=978. This book contains three parts: domestic and foreign policies and regulations, technical papers, and list of green electronic product manufacturers. It includes the Administrative Measure and related standards, regulations in English and Japanese. It is about 500 pages. If you are interested in this book, please contact: Contact Phone No.: +86-10-6820-7850 Fax No.: +86-10-6827-3279 Contact Person:Mr. LiDong QIN ( 秦立东) Address:Room 215, Building 13, No. 27, Wan Shou Road, Beijing 100846, China ( 北京市海淀区万寿路 27 号 13 号楼215, 邮编：100846) E-mail: mailto:c...@cqae.com c...@cqae.com Web Site:www.cqae.com __ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email __
Re: What is killer joules?
On the other hand my ICD supplies 35 joules at full power. Not sure of the voltage. Bob Heller 3M EMC Laboratory, 76-1-01 St. Paul, MN 55107-1208 Tel: 651- 778-6336 Fax: 651-778-6252 John Woodgate jmw@jmwa.demon.c o.uk To Sent by: emc-p...@ieee.org emc-p...@ieee.org cc Subject 08/18/2007 01:18 Re: What is killer joules? PM In message web-153134...@california.com, dated Sat, 18 Aug 2007, Robert A. Macy m...@california.com writes: Thanks to all who answered this question. The culmination of information: 350mJ is safe 20J is lethal I find your conclusions questionable and I would advise great caution. It was pointed out to you that 350 mJ stored in a supercapacitor at 2 V is most unlikely to be lethal if applied to a person's skin, but a far smaller charge could produce a lethal current if applied below the skin. -- 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 __
