Re: Cap Formulas (fwd)

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---------- Forwarded message ----------
Date: Sun, 10 Dec 2006 08:22:55 -0800 (PST)
From: Mike <megavolts61@xxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Cap Formulas (fwd)

Hi Victor,
     First of all, you need to have the puncture voltage be 1.414 x the
voltage out of your pig...and being that it's high frequency, I'd say
double that even.  The formula for capacitance using measurements in
inches is C(microfarads) = 0.224*E*A/(1,000,000*d)  Where E is the
dielectric coefficient, A is the area of the 'plates' in sq. inches, and d
is the distance between the plates in inches.  Also...most people making
homemade caps use either polypropylene or polyethylene for the dielectric.  
I don't know how well mylar can handle high frequency....but my guess is
not very well.  Perhaps someone else on the list knows about that better
than I do....I just know most would use 'poly'.  From memory, I'd guess
that for a single cap to take the whole voltage of your pig, about 90 mils
thickness of polyethylene or polypropylene is required.  It's generally a
lot better to put two (or more) in series so neither cap has to withstand
the entire voltage.
  Mike
   
   
  Can any one help me with calculating the required area (length of 
plates) to
make a rolled cap using the following;

 

20” wide by XX long aluminum flashing

24” wide x .007” thick x XX long Mylar film

 

With a dielectric constant of 3.0 and a puncture voltage of 7500v I 
figure
that I can make two 0.1uf @ 52.5kv for a total of 0.2uf for my 14.4kv 
10kva
pig.

I will be immersing the roles in mineral oil.

 

Any ideas or comments?

 

Victor


 
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