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Re: Power Factor Capacitor -- Was -- RE: schematics...Adam Smith's
<snip>
> > 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.
> >
> > Mark
>
> Mark,
>
> Don't you believe it! :^)
>
> While it is possible to briefly run back-to-back electrolytics on AC (as
> in motor-starting applications), you never want to apply AC directly to
> a single electrolytic capacitor or even an AC motor starting capacitor
> for any length of time. Under the reverse polarity half-cycles, the
> capacitor's thin dielectric layer (thin aluminum or tantalum oxide) is
> eroded and then rebuilt on the next half-cycle. This results in
> excessive internal heating and can result in actual dielectric
> breakdown. Severe internal heating inside the capacitor roll will
> typically rupture the capacitor's safety vent (if you're lucky), or
> cause it to explode (if you're not so lucky). I've seen epoxy-bodied
> tantalum "bullet" capacitors explode with the force of a firecracker due
> to internal buildup of gas and/or steam during accidental application of
> reverse biasing.
>
> For Tesla Coiling Power Factor Correction, only use film-type caps!
> Trust me on this one, Mark... :^)
>
> -- Bert --
Ok, Ok. I get the pitcure.... I don't want to spend my time cleaning up "cap
guts" if one blows up.... The problem is that I've exceeded my budget already
:-( and was trying to find some way to shave a few $$$ off.... I'm sure
everyone
on the list has experienced THAT problem before :-)
Mark