Ian, This is a very good question.
Not that long ago we were qualifying a power supply that would shut down and restart each time it saw the Surge pulse during the 4-5 test. We told the PSU manufacturer that their product fails Surge but they came back and told us that, according to the standard, as long as the power supply returned to normal operation when the test was complete, it passes. As anyone would know, the immunity tests are system tests and if the power supply shut down causing your electronics to reset and causing a loss of data then the system would FAIL. So, we have specified that the output of power supplies must not cause our electronics to malfunction during the 4-4 or 4-5 tests. We specify that the DC output of a power supply can not go "out of spec" during these tests. It is very hard to verify this because the transients caused during the test will couple into the measuring device, such as a scope or meter. If someone has a good method to test this I would be very interested in hearing how. If you filter out the transients then you maybe blinding yourself to what's really happening on the dc output. Brian ____________________Reply Separator____________________ Subject: Burst and surge tests Author: [email protected] List-Post: [email protected] Date: 5/18/2006 9:46 AM Dear Group, I have a question regarding the likely behaviour of ac to dc switch mode power supplies during fast transient burst tests to EN 61000-4-4 and surge tests to EN 61000-4-5. For a manufacturer to claim conformity to these standards are any constraints placed on the behaviour of the dc output voltage during the tests? I am particularly interested in the likely change in DC voltage output as the appropriate burst/surges are applied to the ac input. Many thanks in anticipation of your replies. Best regards Ian Unwin Lead Engineer Servomex Group Limited ********************************************* *Register now at www.servomex.com/zap.html * *for an opportunity to win a great prize * *in our monthly draw. * ********************************************* ________________________________________________________________________ This email has been scanned for all viruses by the MessageLabs SkyScan service. This electronic message contains information from Servomex which may be privileged or confidential. The information is intended to be for the use of the individual(s) or entity named above. If you are not the intended recipient be aware that any disclosure, copying, distribution or use of the contents of this information is prohibited. If you have received this electronic message in error, please notify us immediately. Activity and use of the Servomex E-mail system is monitored to secure its effective operation and for other lawful business purposes. - 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] 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 [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
