To David,
At a power factor of 0.5 the power meter just measures 50% of your assumed power. (but you meant to say write of course) I agree that the power utilities always try to rip us off, but they have more sophisticated means than denying physics. I have personally been involved in measuring over 40 amps of neutral conductor (@150 Hz) current in a building stuffed with ITE equipment, where only 10-16 A rms per phase was measured. The neutral conductor was a 1.5 mm2 wire, and the phase conductors were 2.5 mm2 So I assure you that harmonics can be hazardous if ignored. To John: “ Limiting apparent power requirements” Right and “harmonics current” is another way of saying that. “ the I^2R losses represent an economic loss to the industry, but the supply industry experts say it is not a significant issue” But I personally would be more than happy getting paid the insignificant amount of money lost by I^2R losses !!! ;<)) A IGBT costing less than 5 dollars per phase is able to control a load of 10 kW easily at say 5 or 10 kHz. It is not even difficult to have a power factor of 1 with the right Topology. You will need large inductors to smooth out the switching frequency or active power factor correction circuits that at a nominal current level of 10-20% of the mains current to be corrected, are able to smooth all current irregularities, so a pure sinus current in phase with the mains is consumed. The power loss is about 0.5 % of the corrected power stream as the injected current is out of phase in the opposite way as the harmonics of the main power stream, and as these devices are also switched, and have an efficiency of 90% or better. Gert Gremmen Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Spencer, David H Verzonden: maandag 26 april 2010 13:31 Aan: EMC-PSTC@LISTSERV.IEEE.ORG Onderwerp: RE: [PSES] Harmonic Emissions Testing My understanding was that the harmonics standards were largely driven by the power utilities and billing. With a power factor of 0.5 they were only billing 50% of the power consumed. That examples of large voltage drops on the neutral-ground bus bar in service panels were exaggerated or anecdotal. However that could be hear say or heresy ;) David - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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 <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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 <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com>
