Re: Power Factor Capacitor -- Was -- RE: schematics...Adam Smith's
> Original Poster: "Mark Broker" <broker-at-uwplatt.edu>
> > a PFC cap is a capacitor that is normally used before the load ( NST
> > etc) it is wired in paralell with the 120V system altho most PFC caps
> > are of low values ( uF wise) you end up having to parallel several
> > together to get a hi enuf value to be effective
> > if you are looking for PFC caps be sure to look for "Motor Run" caps
> > ... the "motor start" caps are cheaper for the amount of uF but...
> > they dont hold up well in extended usage ( motor start caps are used for
> > a brief moment when the motor starts, then they switch off)(( they just
> > offer a surge to help out starting torque))
> > most motor run caps are oval shaped and about 2 times taller than they
> > are wide usually they are in a metal case too ...
> > Scot D
> Actually, I've been told that Aluminum Electrolytic will work for a 120VAC
> PFC cap. These are inexpensive and very common. And to head off criticism
> that Aluminum electrolytic caps shouldn't be used in an AC circuit, I was
> told by an Electrical Engineer (Technician?) who runs all the electrical
> labs here at school. He said that electrolytics can take the AC, just not a
> constant negative DC bias.
They are terribly lossy when momentarily reverse-polarised. And
when reverse polarised for any length of time are apt to explode. I
wouldn't take that advice. Back-to-back is OK if leakage currents are
close to identical.