[time-nuts] HP and other equipment failure
J. L. Trantham
jltran at att.net
Sat Jun 15 17:52:52 EDT 2013
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.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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