[time-nuts] HP and other equipment failure

stan, W1LE stanw1le at verizon.net
Sat Jun 15 18:56:22 EDT 2013

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 
   in the electrical power distribution system.

Could be a serious EMC problem if you were dealing with voice grade 
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-bounces at febo.com [mailto:time-nuts-bounces at 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.YahooMailNeo at 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.

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