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Re: Capacitors
Quoting Richard Hull <hullr-at-whitlock-dot-com>:
> Does your cap glow with corona when it is run? Put two or
> three in series until no corona exists.
Jim asks:
> In this old post to Julian, you mentioned a corona glow in a
> polyethylene cap. Is this under oil? That is: can you see a
> corona in a poly cap under transformer oil when you run it
> close to it's maximum voltage level?
Pardon me for jumping in. I have never seen corona under oil.
Oil is like the _ultimate_ corona supressor.
> I'm asking because I've blow my 4 home rolled caps. Each was
> evacuated to <10^-2 torr, filled with oil and then pumped down
> again. I am guessing that I am just over voltageing my caps but
> will watch for corona if it is observable.
I doubt you will see much under oil. The caps likely failed
because they were overvoltaged, or they were not fully broken in.
Even pumped caps will survive higher voltages longer after the
oil has a chance to permeate the entire capacitor. Even a
pumpdown and an entire month under oil does not mean the
capacitor has reached it peak breakdown voltage rating.
Realistically it takes a pumpdown, 30 or more minutes of
intermittent operation, and about 6 months under oil for the
capacitor to reach maximum breakdown voltage. Until these
qualifications have been met, I run homemade caps in series.
Even after, I run them in series because I try to baby them.
Richard Quick
... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12