[Amps] Test versus working voltage for oil filled capacitor

[Jim Thomson]

Date: Tue, 14 Apr 2015 21:14:15 +0100
From: Alan Ibbetson <alan at g3xaq.net>
To: amps at contesting.com
Subject: [Amps] Test versus working voltage for oil filled capacitor

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?

73, Alan G3XAQ

##  They will run fine at 3 kv no load.   Dunno about 2A ripple current though.
They are light.  Mine were from henry radio, made by CDE.   8 x 4 x 12  and weighed
30 lbs each, rated at 42 uf @ 4500 V.     Mount them vertically. 
Also insulate them from any metal chassis, and metal sidewalls....and also from 
the 2nd oil cap.     IE:   Treat them  like hv electrolytics.  If you see oil stating to leak
around the insulators, stop using them.  Your caps are no doubt pulse type rated caps,
and they usually have high ESR.  On any pulse rated oil cap, don’t runt them at any more than
60% of their stamped rating. 

Jim  VE7RF