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Re: [Amps] Test versus working voltage for oil filled capacitor

Subject: Re: [Amps] Test versus working voltage for oil filled capacitor
From: "Roger (K8RI)" <>
Date: Wed, 15 Apr 2015 09:14:16 -0400
List-post: <">>
I was going to say the same. We used 1 to 4 of those big, heavy, oil filled caps in a resonant circuit for induction heating down in the KHz range running 100 to 250 KW. The coils were 1/2" copper tube up to 2 feet long and about 8" to 10" in dia and about 2" turn spacing with water running through when the power was on. The biggest problem was getting the coils to hold their shape during a prolonged run.


Roger (K8RI)

On 4/14/2015 6:06 PM, Carl wrote:
Actually they sound totally unsuited for the job at anywhere near the marked voltage, those are energy storage caps for some industrial pulse type of operation as seen by their feather weight. My 51 uF 9KV "real cap" is about 135# and the pair of 16uF 4KV used in the 1500W 2M amp are about 20-25 # each iffn I remember from when I built it over 30 years ago.

At 3000V maximum they should be fine but Id certainly take precautions when mounting them; vertical mounting only also.

----- Original Message ----- From: "KA4INM" <>
To: "amps" <>
Sent: Tuesday, April 14, 2015 4:48 PM
Subject: Re: [Amps] Test versus working voltage for oil filled capacitor

On 04/14/2015 04:14 PM, Alan Ibbetson wrote:

I have a pair of jumbo oil filled capacitors. They are each 6 x 6 x 12
inches and weigh about 10 pounds. I wish to use them at 3KV off load and
with a 2A ripple current under full load.

The only markings I can read are 42uF and "test voltage 7500 volts" (in
French).  What is the consensus on the likely safe working voltage? Is
it likely to be well defined for this type of capacitor, in the sense
that all have a standard de-rating factor applied?

I would Hi pot it to 7600 Volts and if OK I would use them to 7500 Volts, but their nature and robustness is still unknown they could have
been built to do any of several jobs not related to PS filtering,
  Ron  KA4INM - Youvan's corollary:
                Every action results in unwanted side effects.
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