Re: why does Capacitor break???

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Tomas,

Many capacitor dielectrics will heat up with high frequency. Caps 
should be selected for their rep rates, lead construction techniques, 
dielectric material, rms current capability, voltage, etc. Even 
though many caps are rated for high voltage, they are not rated for 
high frequency. It's best to use caps the coiling community has tried 
and determined good for coiling. You've probably seen on the TCML the 
mention of Cornell Dubilier MMC's. There are Cornell's 940C series. 
They are axial lead film caps which use polypropylene as the 
dielectric (excellent for high frequency) and they have a high dV/dt 
rating (high peak currents). The MMC is very simple. It's just a cap 
bank built of several small capacitors which are series connected for 
the voltage rating. Strings are then paralleled for the capacitance 
required. That is at least the basics. You can play with MMC 
configurations here.

http://www.classictesla.com/java/javammc/javammc.html

I just saw a post of someone looking to do a bulk buy on MMC's. I 
usually buy caps as needed and only when it's right for my pocket 
book. If I need caps, I'll likely contact Dr. Resonance. He uses them 
for his own business and also puts in requests on his order for those 
on the list who also need caps. This increases his quantity break 
down pricing if the extra request quantity is high enough (if the 
quantity is not high enough, he won't get the pricing break. Standard 
operating procedure for those who deal with this stuff on a daily 
basis). However, his MMC needs will vary as will list member needs. 
Contact Dr. Resonance for pricing. I know he's currently looking for 
coilers in need of caps.

Take care,
Bart

Tesla list wrote:

> Original poster: Tomas Stankevic <Tomas.Stankevic@xxxxxxxx>
>
> Hi, today I tried my first Tesla Coil. It's 65cm high (secondary), 
> it is powered by 10kV 20mA transformer (a bit too low for him). I 
> used 25kV, 22nF capacitor. It worked perfectly for about 20 minutes, 
> then capacitor went hot and then it was dead. Why?? transformer 
> power supply is 10kV and a capacitor is suitable for 25kV! I know 
> about a resonance... but... :( What capacitor should I use then???