I read in !emc-pstc that [email protected] wrote (in <OF62D8BA72.6A045F [email protected]>) about 'EN 61000-3-2' on Mon, 3 May 2004:
>John, are you sure? Well, yes, in one way I'm sure, because that's the real issue involved in practice, but I agree it's not what the standard says. The 75 W lower bound applied specifically in the previous edition to Class D only. Since the Class A limits are fixed current limits, it's not possible for a product drawing less than 2.3 A from the supply to fail to meet the 3rd harmonic limit, or one drawing less than 1.14 A to fail to meet the 5th harmonic limit. This same reasoning applies to harmonics of all orders. Unless a product drawing 75 W or less had a pathological harmonic signature, e.g. producing more than 58 mA of 39th harmonic and/or more of any lower-order odd harmonic, or an even larger amount of even harmonic, it could not fail the Class A limits. So the committee considered that it was permissible, on the basis of the physics, not in terms of impact on the supply system, to extend the lower bound to Class A and Class B products, unless any problems resulted from that. This means that such low power products do not need to be tested, which is clearly a cost-saving for manufacturers. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [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: http://www.ieeecommunities.org/emc-pstc
