Hello John:
For the benefit of the members of this group (you know the answer as well as I do)... > > Leakage > >current is measured with a leakage current > >meter that doesn't read the higher harmonics > > Why? Don't the harmonics (and SMPS effluent) contribute to > shock hazard? The leakage current measuring network shown in IEC 60990 emulates the body's response to higher frequencies as described in IEC 60479-2. As frequency goes up, the body response (compared to mains frequency) goes down. For example, if the threshold of perception at mains frequency is 0.5 mA, then at 1000 Hz the threshold of perception is 2.2 times higher, which is 1.2 mA. The leakage current meter accounts for the body response to frequency. For 1000 Hz, 1.2 mA, the leakage current meter will indicate 0.5 mA. The GFCI does not have this frequency compensation; the GFCI will trip when the rms current difference is 5 mA regardless of harmonic content. So, while the leakage current measurement may indicate a value less than the GFCI trip current, the actual line-to-neutral difference current can exceed the trip current. Best regards, Rich Richard Nute Product Safety Consultant San Diego - 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/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: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________
