Re: Success - Was in agony.

[Esondrmn-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

In a message dated 8/24/00 10:13:17 PM Pacific Daylight Time, 
tesla-at-pupman-dot-com writes:

 - snip -
<< 
 The NST is 12/30 I calculate the impedance at 400,000.
  
 The cap is a plate stack cap with 12 mm polyethelene sheeting between the
 plates. Not soaked in oil yet, I got to get some but disregarding this, the
 area of overlap is 26 square inches per plate. What do you think I should 
have
 in plates for a LTR cap. I tried to calculate it but the results I get don't
 make sense. The value is .066 for a resonanat cap but I don't know if this is
 PF or UF or what. I figure I might want about 80ish for each cap.
  
 What do you think I should shoot for and how many plates do you think I need?
  
 I am sorry to bug you folks and asking this but I think I need some straight
 figures that I can work with and compare and figure out where I went wrong in
 my calculations. >>

Gary,

Is the dielectric material 12 mm thick?  If you mean millimeters, this is 
.47".  Therefore, I think you mean .012" thick.  First, this is quite thin 
for a tesla primary cap.  I used .064" and was able to puncture it with a 12 
kv neon sign transformer.  .090" thick is needed for 12 to 15 kv 
transformers.  If you are using 12 .001" thick sheets it would be better than 
one sheet that is .012" thick.  The capacitance formula (from memory) is:
C (pf) = .225 K A / d  where K is the dialectric constant of the insulator, A 
is the area in square inches and d is the distance between plates in inches.  
Using 3 for the dialectric constant (I don't have my chart with me) and 26 
square inches for A and .012" for d, we get .00146 microfarads for two plates 
and one sheet of dialectric.  They add in parallel as you build up the stack. 
 To get .01 microfarads, you would need 7 sheets of dialectric and 8 metal 
plates.  

I think you only need between .008 mfd to .01 mfd for this coil.  I have two 
coils, one is 14.4 kv  5kva with a 6" secondary, running around 100 khz if I 
remember and it uses a .05 mfd cap.  The other is a small 3" diameter 
secondary using a 12 kv 60 ma transformer and it uses only a .0084 mfd cap.  
I don't remember the specs on your coil so I don't know what frequency we are 
shooting for.

If you provide all the information on your primary and secondary, I will run 
some calculations for you.  By the way, I bought the two caps for my small 
coil from Dr. Resonance for I think $25.00 each and they run great.  This 
would be another alternative to making an mmc capacitor.  By the way, I would 
never fire up a rolled or flat plate poly cap without being immersed in oil, 
with all the air bubbles out.

Ed Sonderman