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capacitor building info





---------- Forwarded message ----------
Date: Wed, 1 Oct 1997 19:40:07 +0100
From: Gwyn Zucca <gwyn-at-tcbod.demon.co.uk>
To: tesla-at-pupman-dot-com
Subject: capacitor building info

Hello All,


Following the recent exchanges about the use of paper in home made pulse 
capacitors, I have been speaking with one of the people at a company 
that specialises in high voltage, high energy capacitors.

The guy seemed quite happy to talk to me about the way they construct 
there caps. He does not advise the use of paper in home made caps due to 
the difficulty in removing moisture in the paper, however he did give me 
some tips on the does and donts.

He says obviously that everything should be as clean as possible.

Use the thinnest dielectric that is possible, they use polypropylene in 
the range 10 - 18 microns depending on application.

Use multiple layers of the dielectric material here again they typically 
use 2 - 4 layers.

Limit the electrical stresses, by using many series modules of high 
capacity to get the appropriate value, for a cap having an AC rating of 
15Kv, he advises 10 - 12 series units, he says that they would never 
exceed 1500 volt per unit in there professionally built capacitors.

Using 4 layers of a good quality polypropylene film in oil he says 10 
volts AC per micron of dielectric would be fair.

They use foil of 5 microns thickness, here again the home made caps have 
to compromise, but try to keep the foil to less that 20 microns 
(barbecue cooking foil typically fails in this area ).

All connections and bushings should be of a heavy duty construction, 
best 
to over engineer it, than be of an inadequate design.

I plan to do some design and experiments in the near future using 6 
layers of 4 - 6 layers of 25 micron polypropylene film, which can be 
obtained from companies who specialise in retail packaging. The caps 
will probably have 12 modules in series, the whole being in oil.


I would like to hear yours views on this.


See ya...


Gwyn