Rich, Thank you very very much.
taniagr...@msn.com ----- Original Message ----- From: Rich Nute Sent: Saturday, August 18, 2001 3:02 PM To: taniagr...@msn.com Cc: j...@jmwa.demon.co.uk; emc-p...@majordomo.ieee.org Subject: Re: CE test suite for computers Hi John and Tania: Actually, the harmonic current problem is no different between Europe and North America. The basic problem is that the harmonic currents generated in the load equipment are dissipated in the delta primary of a delta-wye distribution transformer. If the harmonic content is large, then the primary winding can overheat, resulting in transformer failure. In North America, distribution transformers are relatively small. Three-phase is not used in the home, so the problem only shows up in commercial and industrial sites. The distribution transformers are largely owned by the business, not by the power company. North America has incurred such transformer failures. The problem has been publicised, and transformers are now designed using a "K" factor which indicates how much harmonic current the transformer can safely handle. In Europe, the distribution transformers are relatively large. Three-phase is distributed to homes. A single transformer can supply up to 600 homes and businesses. (In North America, the transformer supplies 8 homes maximum.) It is relatively rare for the business to own the distribution transformer. Failure of such a transformer can be quite disruptive. So, in Europe, rather than replace the very large distribution transformers, the power supply industry is imposing harmonic current emission limits on electrical products. Harmonic currents can cause other problems. But, this is my understanding of the reason behind EN 6100-3-2. Best regards, Rich ------------------------------------------- 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: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"