[Amps] Using an oil capacitor

David C. Hallam dhallam at knology.net
Sun Jun 19 08:09:42 PDT 2011


Pulse rated oil capacitors must be derated for use for a linear power 
supply use.  2/3 might be safe but 1/2 is better.

David
KW4DH

On 6/19/2011 1:59 AM, Vic K2VCO wrote:
> I have an oil capacitor rated at 53 uf 3.5kv. I would like to use it in a power supply
> with a transformer delivering 2.4 kVAC. The peak voltage is thus close to 3400V.
>
> I've never used an oil capacitor before. My line voltage is pretty constant at 240V, but
> if it were to rise to 250V, the voltage rating of the capacitor would be exceeded. What
> kind of safety factor do capacitors like this have?
>
> The capacitor is 4-1/2" x 4" x 10" and is marked CSI 4W308T. The CSI website
> <http://www.csicapacitors.com/csite/cms/149.htm>  doesn't list this particular one, but
> other 3.5kV capacitors have similar part numbers. There's no detailed spec. There is this
> statement:
>
> "The WM series of capacitors is designed for general purpose pulse applications in power
> supplies for lasers, flash tubes and other capacitor discharge circuits where moderate to
> long life is required."
>
> I'm not sure if this is appropriate for power supply filter application. Anybody familiar
> with these?

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