I read in !emc-pstc that Chris Chileshe <[email protected]> wrote (in <[email protected]>) about 'Baffled by EFT test results (EN61000-4-4)' on Fri, 25 Oct 2002:
>This is probably the first time I have seen anything get through transients >testing without any explicit measures to mitigate against failure. Has anyone >experienced this? Is there an explanation for this? Yes, sometimes you get lucky! > >I have always used varistors almost as a matter of course, so you can >understand >my surprise. > >Could it be I have "over-designed" my RF filter to the point it is good >enough for the EFTs as well? The caps are only rated for 50V though ( the >clamping > voltages of the varistors). If you can afford it, you haven't over-designed it. (The converse is not, unfortunately, always true.) > >Could it be the caps are in fact rated for such transients although this may >not >be stated explicitly? Should I prolong the exposure of the varistor-free >circuit >at >2kV to see if I am dealing with "delayed failure" potentially? I have been >setting >my burst duration to 1 minute. Without knowing what type the capacitors are, and the exact circuit configuration, one cannot say. How much of the 2 kV actually appears across the caps? (Measure, it might not be what you expect). Leave the varistors in if you can afford to and they don't cause a problem if/when they explode. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
