RE: Capacitor value not clear yet.

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Again,

I should point out why one should never short across a primary cap (or put 
a spark gap directly across the primary cap).  If you have a straight piece 
of wire that you short that cap with, there is very little 
inductance.  Then Z may only be say one ohm (mostly in the big bright arc!).

20000 volts / 1 ohm = 20000 amps!!!

That can destroy a cap!!!  Best to use bleeder resistors IMHO.  Or, get a 
big power resistor of about 1000 ohms and put it on a long insulated 
plastic stick.

Check out Bert's site about using giant super high current caps to crush 
quarters:

http://205.243.100.155/frames/shrinkergallery.html

A little over 1,000,000 amps there ;-))

Cheers,

         Terry


>Hi Luke,
>
>The primary current is a function of the primary resistance, frequency, 
>and inductance.
>
>If the resistance is 0.1 ohms and the inductance is say 100uH and we have 
>a 20000 Volt primary cap at 20nF, we can find the peak current.
>
>The inductance will have a value Zl which is generally referred to as 
>complex impedance or reactance.  This acts much like resistance.
>
>Zl = 2 x pi x Fo x L
>
>Fo = 1 / (2 x pi x SQRT(L x C)) = 1 / (2 x pi x SQRT(100e-6 x 20e-9) = 
>112540Hz
...........