Ralph McDiarmid <[email protected]> wrote (in <[email protected]>) about ''Variability' of mains harmonics', on Tue, 19 Jul 2005: >I suggest that the inductive component of the mains impedance is a >large contributor to the variation in harmonic amplitude measurement. >It may help to specify the real and imag components of that impedance >in the testing standard. (e.g.. an AC voltage source with a known >impedance in series)
IEC 61000-3-2 doesn't do that, for reasons that have convinced those concerned. (If the source impedance is not very low, the resulting input voltage distortion affects the current values in a complicated way, and unless the impedance is VERY closely controlled, the spread of results when different sources are used gets even bigger.) Instead, it sets limits on the voltage distortion at the EUT terminals, and those limits imply a VERY low source impedance, much lower that most (under 16 A/phase) equipment has in series with the rectifier. This has the 'side-effect' of MINIMIZING the conduction angle and thus exaggerating the harmonic amplitudes. Guess why the electricity suppliers are in favour of it. (;-) The Japanese 'experimental' standard based on IEC 61000-3-2 doesn't do that; it specifies a source impedance, which may or may not be representative of the source impedance of the typical Japanese household supply. -- Regards, John Woodgate, OOO - Own Opinions Only. Deadlines are 90% of deadliness. http://www.jmwa.demon.co.uk Also see http://www.isce.org.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 [email protected] Instructions: http://listserv.ieee.org/listserv/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: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
