List I would like your precious opinion about a situation regarding harmonic current measurement (61000-3-2).
First case: Using a sinusoidal AC power source, with a controlled output voltage (almost perfect sine, voltage THD lower than the needed, even with load), I measured the current harmonics using the internal instrument of the power source. The 13th and 15th harmonics were right above the limits (Class A limits). Second case: I add a digital wattimeter to measure the harmonics. The harmonic content became 30% lower than the first case (good enough to pass). And I got this results with the two instruments (the one inside the power source, and the wattimeter). My first thought was the increased impedance due to the wattimeter (Zm). But I got 50mV of drop voltage in this instrument (peak voltage), that is lower than the specified in 61000-3-2, Annex B (0,15Vpeak maximum). And the impedance of its current shunt is only 0,008 ohms (data from its manual). This put my first guess down ! Theoretically, the wattimeter couldn't attenuate so much the harmonics ! Any idea of what could be happening ? Thank you again. Günter J. Maass Researcher - Power Electronics Development EMBRACO S.A. ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
