In message <of0fde0d28.d5a757d8-on88257634.007df0e7-88257634.007f6...@slpower.com>, dated Thu, 17 Sep 2009, [email protected] writes:
>Testing may have shown that some mains transformers have problems with >successive half-sines of the same polarity. For example, ' + - + _ + >- +' (the underscore is a half-cycle dropout at 180 degrees.) If they had 'problems', the product would be unreliable in the field. That is not a subject for EMC testing. The effect on the transformer is to cause acoustic noise and mechanical vibration. There is likely to be a large inrush current, but that is investigated when testing to IEC/EN 61000-3-3. I don't see why IEC 61000-4-11 is concerned with that. The vague phrase: "Shorter durations in the table, in particular the half-cycle, should be tested to be sure that the equipment under test operates within the performance limits specified for it ." [i.e. Criterion A applies!] should not be there. It pre-empts a decision as to which criterion (NOTE: the singular is 'criterion', not 'criteria') A, B or C to apply to the test. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Things can always get better. But that's not the only option. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
