RE: Please help with capacitor

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

A home made cap used with a 15kV power supply must be made from at least 2 
or 3 individual caps, in series.  A single
cap will fail due to corona at the edges of the foil.  I spend a huge 
amount of effort on two attempts at rolled poly caps.  The first used a 
single layer of 40 mil poly, and dies after a few minutes.  The 2nd attempt 
was made with two units in series, each with a single layer of 40 mil 
poly.  It too died after several minutes (see 
http://www.laushaus-dot-com/tesla/rolledcap.htm).

Assuming you are using 60 Hz power, your cap is mains-resonant with the 
NST, and this is a bad thing.  In addition to being healthier for the cap, 
I have found that a value of about 2X the mains-resonant value gives the 
best performance with a static gap.

Regards, Gary Lau
MA, USA

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, January 05, 2004 7:09 PM
To: tesla-at-pupman-dot-com
Subject: Re: Please help with capacitor


Original poster: "Philip Brinkman" <peeceebee-at-mindspring-dot-com>

I'm making a new flat plate capacitor for use with my 15,000 volt 60 ma
NST. I'm using aluminum foil plates 7.5"x9" (67.5 sq. in.) with 30 mil
polyethelyne (6 layers of 5 mil each) between each plate. Using the formula
C=kA/d (k=2 ) I get 3.25 sq. meters or 74 plates, does this sound right? My
last capacitor had only 30 plates. I'm aiming for .013 microfarads.. is
this right? Using different programs I get different values of capacitor to
use.