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Re: Results of Paper & Poly & Oil
---------- Forwarded message ----------
Date: Mon, 29 Sep 1997 07:08:58 -0700
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Results of Paper & Poly & Oil
<SNIP>
> "wasted" edge matierial that contributes to HV holdback, but not to
> capacitance, the capacitance of the new capacitor is much less than
> the original. The original was .01 mfd, and the new one is now .007
> mfd. Total poly thickness between plates is 120 mils. Not my ideal
> configuration, since I am using two 60 mil sheets of polypropylene
> plus paper between plates. I would have preferred splitting this into
> two .014 mfd caps and then put them both in series. This would have
> been much better, but would have required two containers. Sometimes I
> do things that I know are not optimal, simply because I happen to
> already have this or that item on hand. That's life, folks!
>
> Hope this helps.
> Fr. Tom McGahee
Fr. Tom,
Great post! I fully agree with your comments on using an absorbent paper
- Kraft paper is very inexpensive and its what the professionals use.
Especially interesting is the discoloration where the paper has been
physically altered by the action of the corona. This effect is also
observed in high voltage oil insulated cables used in power
distribution. Are your sheets of kraft paper the same size as your poly
sheets, and did you see any signs of tracking on the ends? What voltage
levels were you running on this unit?
Your results certainly add support to the idea of making the caps from
identical series sections to reduce the voltage stresses seen by each
section. Another benefit, however, is that since each cap sees less
voltage, more dielectric area could be used on each, making for
significantly higher volumetric efficiency. However, I'm not sure I
understand why reassembling these as two 0.014 uF caps connected in
series would require 2 containers. Shouldn't you be able to fit the
multiple-sections in a single container? The flat caps I'm using
actually consist of four identical sections, connected in series, in one
container. Unfortunately, I didn't use kraft paper when they were
built.. :^(.
Thanks for the info, and safe coilin' to you!
-- Bert H --