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Re: A new cap failure mode?
At 21:29 5/02/99 -0700, Bert Hickman wrote:
... snip ...
>> 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.
... snip ...
>So THAT's why it makes such a loud bang! :^)
>
>While the instantaneous currents can be quite high, the duration is also
>very short, and the physical inertia of the elements in either a rolled
>or flat-plate cap should prevent damage from electromagnetic forces. An
>exception might be the very thin metalization in a ceramic doorknob cap,
>but even here, the dielectric itself will generally limit the maximum
>rate that energy can be "extracted".
Hi Bert,
Hopefully my other post will appear at some stage, but why not take the
energy through the primary ?
That is,have the safety gap discharge into the circuit by having it in
parallel with the RSG, not across the cap. This will provide the same
protection in the charging phase at 50-60 Hz surely ....... or is my lack
of EE training showing through YET AGAIN ;-)
I would put to the assembled masses that:
1. Safety gap across the cap is superfluous in a static gap system. If
the safety gap breakdown V is significantly greater than the SG (as it
would be), then I can't see how it would ever function.
2. For RSG systems, a parallel static SG is the appropriate protection
circuit.
Donning iron clad asbestos suit & ducking for cover ;-)
cheers
Mark
http://www.cobweb-dot-com.au/~dkfinnis