Sorry for the interruption but what is 'PFC'? Thanks.
Joe -----Original Message----- From: [email protected] [mailto:[email protected]] 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 <[email protected]>, 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 [email protected] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
