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Re: A new cap failure mode?



In a message dated 2/5/99 5:26:36 AM Pacific Standard Time, tesla-at-pupman-dot-com
writes:

> 	In an off list discussion, a topic came up that I have not seen before but
>  I always assumed may be a factor in capacitor failure.  
>  
>  	When one places a nice safety gap across a capacitor, and it is firing for
>  any reason, what is the current in the discharge pulse?  Since Tesla caps
>  are designed to be very low inductance and low resistance, there is very
>  little limiting the current when the safety gap fires.  If a cap is charged
>  to say 20kV and the resistance of the mess is say 0.5 ohm - we get 40000
>  amps!!  That is enough to do some real internal damage to any capacitor.
>  The suggestion comes up that perhaps a safety gap placed directly across a
>  primary cap needs a little resistance in the circuit to keep this current
>  to a "safe" level.  
>  
>  Comments or suggestions are welcome...
>  
>  	Terry
>  
Terry,

Good point.  When I was having primary problems a while back, and the cap
safety gap was firing, it sounded like a shotgun - scared hell out of me the
first time it went off.  You know there is a lot of energy being dissipated
there.

Ed Sonderman