I read in !emc-pstc that rbus...@es.com wrote (in <B47A89AEC4538744B9D94 bad7e78efc7454...@torino.corp.es.com>) about 'Harmonics Testing for PCs' on Thu, 20 Feb 2003:
>During the Harmonics test (EN 61000-3-2) the system failed harmonics. >Testing all of the peripherals individually, they all passed. As a >system, the only way it would pass is to have both power cords from the >graphics processor plugged into a single phase. That seems very odd: one would expect the harmonic currents from the two cords to add almost arithmetically. Is there any indication that partial harmonic cancellation was occurring? >Obviously this >compromises our ability to balance the input current as well as we would >have liked. > >So my question to the group is: > >1. Why would the arrangement of the power cords affect the harmonic >noise. My guess might be a defective power controller but beyond that I >am perplexed. More data, please: Was the product tested as a 3-phase unbalanced load or a balanced load? What is the active power consumption? Which emissions Class (A or D) does the equipment fall into? Which harmonics were too large and by how much? Does the input current fluctuate a lot? It makes a LOT of difference whether the 5th harmonic or the 37th failed! -- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
