Distortion may not be just on the 120 V lines. I previously worked in a building where the variable frequency drives (VFDs) for the building’s cooling system were causing significant distortion on the 277/480 V lines. There was enough distortion that it carried through to the 120/208 V system through the step-down transformers. The result was that even on the lower voltage system, two of the three phases showed flat topped sine waves.
Ted Eckert Compliance Engineer Microsoft Corporation [email protected] The opinions expressed are my own and do not necessarily reflect those of my employer. From: Ralph McDiarmid [mailto:[email protected]] Sent: Thursday, May 21, 2009 11:14 AM To: [email protected] Subject: Re: 120V mains voltage distortion I've seen some moderately distorted voltage waveforms on 120V mains, I suspect mostly due to narrow conduction-angles with high peak currents, like rectifier-capacitor loads without PFC. (TV and computer power supplies come to mind) Ralph McDiarmid, AScT Compliance Engineering Group Xantrex Technology Inc From: [email protected] [mailto:[email protected]] On Behalf Of John M Woodgate Sent: Thursday, May 21, 2009 10:08 AM To: [email protected] Subject: Re: IEC 60950-1 short circuit test criteria In message <[email protected]>, Ralph McDiarmid <[email protected]> writes >We do have problems with mains harmonic currents in 120/240V, 3-wire >distribution system and there are harmonic emission limits for grid-tie >inverters connecting to the public utility at low voltage. Yes, I meant that problems you have are less severe, excluding hot neutrals. We have voltage waveform distortion, due to the higher supply impedances. -- This is my travelling signature, adding no superfluous mass. John M Woodgate - 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - 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 <[email protected]> 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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]>
