Re: Cap Formulas (fwd)

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---------- Forwarded message ----------
Date: Sat, 9 Dec 2006 20:11:37 -0700
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Cap Formulas (fwd)


In US units the equation is:


        C   =  KA/d x (n-1)


where C is in picoFarads

K is dielectric constant of the dielectric

A is total area of one plate in square inches

d is thickness of dielectric

You just insert your data and solve the above equation for area.


If you plan on using a pole xmfr I definitely would NOT use mylar.  I 
recommend either PP (polypropylene) or PE (polyethylene) as a better 
dielectric choice.  About 90 mil thickness if only one thickness, otherwise, 
use multiple layers (5) of 20 mil sheets.  7 mil mylar will not last very 
long on a pole xmfr.  RF currents produce heat and edge-tracking both which 
can destroy a HF RF cap rapidly.

Also, if rolling your own, be sure to use extended foil construction.  Leave 
a very generous margin on each dielectric edge (3 inch min on each side). 
Wear plastic gloves as the salts on your skin are very conductive and will 
cause your cap to "edge track" at RF frequencies --- the number one cause of 
HV cap failures.  Vacuum evacuate the cap prior to adding the protective 
xmfr oil.

If you need xmfr oil contact me off-list.  I carry it in 55 gal drums and 
could supply a gallon.

Dr. Resonance




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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