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Re: Oil Cap + Paper
Subject: Re: Oil Cap + Paper
Date: Sun, 4 May 1997 12:10:16 -0400 (EDT)
From: DavidF4797-at-aol-dot-com
To: tesla-at-pupman-dot-com
Dear Fr. Tom
> A little while ago there was some discussion as to whether or not adding
> paper to a Tesla coil capacitor would be useful. I have just finished a
> few
> experiments along this line, and would like to share with all of you my
> observations.
>
I did a similar experiment last year with simialr results (although
somewhat
less rigerously) and posted it to the list at that time. Paper between
the
poly sheets, in my opinion, does indeed improve wicking action and
bubble
size reduction. This reduces heating and a major cause of home brew cap
failure. This concept was confirmed later wiht a discussion with Beau
Meskan of Plastic Caps here in Chicago in whic he stated that in thier
experience, even with pumping down!, they never make a poly only
capacitor
with a plate height greater that 3inches since incomplete wicking is
likely
to occurr and cuse premature cap failure.
The only aparent drawback to the paper/plastic leave design is that the
paper
is much more lossy (higher dissapation factor) at TC frequencies than
poly
which can causes it to heat significantly over a long run. This was a
problem for me since at the time, I was usuing Silicone transformer oil
which
has a large thermal coeficient of expansion. This caused the oil to
continuously over pressureize my container and pop the cork on the
filling
spout. The heating, though, because of the reduced size and number of
air
bubbles, appeared to be more even over the surface of the plates (a very
good
thing)!
Generally, I came to the conclusion that for "home Brew" capacitors,
particulary when a vacumme pump is not handy (most of us) the paper
between
poly design was the best, even with its limitations. BTW I remember
getting
some stiff opposition to my notion at the time. Vindication is a
wonderfull
thing! ;)
Great work!
-DavidF-