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Re: Capacitors




>From: Richard Hull <hullr-at-whitlock-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: Capacitors
>
>Tesla List wrote:
[snip]
>>         In this old post to Julian, you mentioned a corona glow in a
>> polyethylene cap. Is this under oil? That is: can you see a corona in
>> a poly cap under transformer oil when you run it close to it's maximum
>> voltage level?
>> 
>> I'm asking because I've blow my 4 home rolled caps. Each was evacuated
>> to <10^-2 torr, filled with oil and then pumped down again. I am
>> guessing that I am just over voltageing my caps but will watch for
>> corona if it is observable.
>> 

>All items corona at some given voltage in oil.  This point is much higher 
>than in air, but still exists.  If you have corona you have ion 
>production, and therefore, conductive paths.  I find that polyethylene 
>coronas around 10KV or even less in some oils.
>  I would recommend a 
>minimum of two poly caps in series if you use 12KVAC or more in your tank 
>circuit.
>
 I think that the 75kV spikes qualify here;( (I'm still not sure that
I believe this value, I may have been a ground loop problem. I've not
had a chance to double check it yet.)

When I roll up my latest sheet of plastic I will keep my pig to 7.2kV
instead of double volting the primary.

	Thank you,

	jim