Re: Polyester Film Capacitors

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Original poster: "Dr. Duncan Cadd by way of Terry Fritz <twftesla-at-uswest-dot-net>" <dunckx-at-freeuk-dot-com>

Hi All!



>Polypropylene caps are the lowest-dissipation high-voltage
high-current
>caps out there

They probably are, but I can't help wondering . . .

Purely out of idle curiosity, has anyone ever seen high voltage high
current rated polystyrene caps?  Based on the dielectric properties of
polystyrene they ought to be pretty good too.  I have an illustration
in a book from 40+ years ago showing metal-cased polystyrene caps of
generous dimensions with the usual massive ceramic standoffs on them
and evidently intended for HT valve circuitry, but the British company
which made them (TMC in Orpington) no longer exists.  Just wondered if
anyone still produces such things.  The only polystyrene caps I've
seen recently are the small signal, low loss 160V jobs for your
average silicon circuitry.  I'm just wondering if there's a good
reason why we don't see hefty polystyrene caps, but from a polymer
chemistry view of things I can't think of a single reason why they
shouldn't be made.

Dunckx