In the classical (transformer -) [bridge] rectifier - storage capacitor
configuration, the capacitor charge current is creating short high peaks
on the current waveform (and therefor truncate the peaks of the voltage
waveform, the distribution circuit resistance being finite), due to the
nonlinear load.
The negative effects are much more due to high current harmonics than
(slightly) capacitive cos fi, and increase the losses in the
distribution circuits.
On 6/16/2013 12:57 AM, Azelio Boriani wrote:
Although off-topic here, the PFC (or power factor correction) is a
switching mode front-end used to correct the cos-phi of the otherwise
capacitive load that every switching mode power supply is for the
mains.
On Sat, Jun 15, 2013 at 11:52 PM, J. L. Trantham<jlt...@att.net> 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.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@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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