An Audiophool and his money are soon parted. -John
=============== > The current distortion from simple transformer-rectifier-capacitor power > supplies contains a lot of third harmonic content. In a 3 phase system > (as are > all distribution systems for commercial and industrial) the third harmonic > ADDS > in the neutral, or creates circulating currents in a delta configuration. > These > currents, as you mention, can get very large and were the cause of many > transformer explosions in cities as these power supplies became common. > The > transformer designs had to be improved, but the PFC supplies make a big > difference. > > How many of you have looked at the power line waveform, especially in an > industrial or commercial area? Doesn't look much like a sine wave, does > it? So > it's pretty funny to see audiophile outlets > (http://www.dedicatedaudio.com/power_outlets). > > Peter > > > > > On 6/15/2013 6:56 PM, stan, W1LE wrote: >> PFC to me is power factor correction, not only the classical power >> factor to >> minimize (VAR) volt-amp reactive component, >> but also to remove the harmonic load current imposd on the electrical >> power >> system. >> A '90's onward technique. in th 80's and 90's without the harmonic load >> current reduction and having >> a few 100 end items of equipment, each withtheir own a switch mode >> power >> supplly, >> it was not uncommon to find hundreds of amps of the third harmonc on >> neutra, >> in the electrical power distribution system. >> >> Could be a serious EMC problem if you were dealing with voice grade >> channels. >> And people safety issues. >> >> Stan, W1LE Cape Cod >> >> >> >> On 15-Jun-13 5:52 PM, J. L. Trantham wrote: >>> Sorry for the interruption but what is 'PFC'? >>> >>> Thanks. >>> >>> Joe >>> >>> -----Original Message----- >>> From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On >>> Behalf Of Poul-Henning Kamp >>> Sent: Saturday, June 15, 2013 4:09 PM >>> To: Robert Atkinson; Discussion of precise time and frequency >>> measurement >>> Cc: Perry Sandeen >>> Subject: Re: [time-nuts] HP and other equipment failure >>> >>> In message >>> <1371329221.83869.yahoomail...@web171902.mail.ir2.yahoo.com>, >>> Robert Atkinson writes: >>> >>>> While I agree with everything else you say, you CAN have too much >>>> filter capacitance. At least where dc rectifier / filter (smoothing) >>>> circuits are concerned. Increasing C causes increased ripple current >>>> [...] >>> And ripple current can be a major source of power-line frequency noise >>> in >>> all electronics. >>> >>> The main reason why switchmode power-supplies today (can) outperform >>> linear >>> power supplies with respect to noise, is because the legally mandated >>> PFC >>> correction eliminates the bridge-rectifier ripple harmonics. >>> >>> I would not hessitate to use a good quality switchmode to replace the >>> linear >>> supply in a HP5370B. >>> >>> I did some experiments a couple of years ago, with an audio-amplifier: >>> I put a standard PFC corrector chip on the secondary side of the trafo. >>> >>> The overall result was not satisfactory, but the 50 Hz "sneer" >>> we all know and hate was absent, and the "Tzoing!!!!!" power-on >>> mechanical >>> shock from the trafo was also eliminated, as was the consequent dimming >>> of >>> the lights ;-) >>> >>> The main reason not to do this, is that you need some physically >>> gargantuan >>> coils for a 10A+ PFC-switcher. >>> >>> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> ----- >> No virus found in this message. >> Checked by AVG - www.avg.com >> Version: 10.0.1432 / Virus Database: 3199/5913 - Release Date: 06/15/13 >> >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
