Re: why does Capacitor break???

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Tomas,

Chances are that your capacitor was not pulse duty rated.
The dielectric was probably a high lossy material like poly-
ester (mylar) that will quickly heat up in the rapid charge/
discharge cyling in Tesla coil operation. Most filter type
caps fall into this category. Your capacitor(s) needs to
be pulse rated with a low loss dielectric system like poly-
propylene or polystyrene to prevent the overheating, which
ultimately causes capacitor failure, as you have found out.
Most coil builders use the Cornell-Dubilier 942C series
snubber capacitors these days in a multiple series parallel
configuration to get the desired voltage standoff and capaci-
tance combination for their coil system, as these caps do
have the right type of dielectric and if designed properly for
the desired voltage, are nearly bullet proof. List member D. C.
Cox (aka - Dr. Resonance) is currently selling these capacitors.

David



----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, April 05, 2007 1:30 AM
Subject: why does Capacitor break???


> 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???
>
>
>