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Re: oil for caps (fwd)
From: Adam[SMTP:absmith-at-tiac-dot-net]
Sent: Monday, January 05, 1998 2:06 AM
To: Tesla List
Subject: Re: oil for caps (fwd)
>>Definitely not so! Ask anyone who has used the Sunsil refrigerator
>>compressor oil, it doubles the capacitors value. Look in the archive there
>>was a big discussion on it several months back.
>What are we doing here creating new physics? The capacitance may increase
>with higher dielectric oil but only because of the space being displaced
>between the foil and the poly. This may make a higher capacitance but it has
>to lower the breakdown voltage by stressing the poly more. You just don't
>get something for nothing. I remember seeing the posts about doubling
>capacitance, but I don't believe it.
I also think it may be exaggerated. The only case where I can see the
oil actually doubling the value of the dry cap would be if it was
_really_ loose and sloppily rolled. Thus, you would have oil filling up
substantial air gaps and increasing the capacitance.
But, consider this mechanism: The cap is not rolled super-tight, but it
is not sloppy either. You add the high-k oil and, over time, the poly
absorbs some of it. The poly increases in k due to the absorbed oil,
swells, and also (due to swelling) presses more firmly against the plates
displacing air and tightening the roll. The combination of increase of k
and increase in "tightness" should give the cap value a significant
boost. I would not expect a doubling, but I've honestly never tested
sunsil-saturated poly to see what its dielectric constant really is.
Just my $0.02
-Adam
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