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Re: Cap Failure



All,
        I had a couple of thoughts on this one last night....

Richard:
> "Well boys and girls, I believe I know why they blow.  Run out to you
> garage, shop or lab and look closely at the printing on the cap casing.
> Yep, the pvc casing is only rated at 10 kvac.  I may assure you that
> the inner rolls are intimately in contact with the inside of the
> casing.  When I closely examined my casing there were several small
> black carbonized tracks in the casing.  Under magnification they appear
> to be arc tracks through the pvc wall.  As pointed out earlier, these
> caps are sealed with the specifications of a bomb.  And, with our
> resonances and kickback I'm sure the 10 kvac case rating is handily
> exceeded."

Ed Phillips:
>     How did the carbon track form?  Was the capacitor sitting
> on something or did it just start to grow along the casing from
> one end?  Can't see how the casing could be rated at 10 (kV) from
> end to end.  Was the breakdown from capacitor section to capacitor
> section (started between them, I mean)?????  Tell us more.  This
> is an interesting and important topic, since I bought a couple of
> the things and have been looking forward to using them.  Wonder if
> there were bubbles or the like in there, and breakdown started
> within the bubbles?  Standing them on end (for a significant period
> of time) might help that, but that arrangement would sure be
> unhandy......

The label is metallic and would span several sections I imagine. If 
that was positioned on top, things could perhaps happen. There is
a bit of non-oil space in the tubing. Questions are: where exactly in 
the case was the tracking observed? Was the tracking thru the case?
If so, was the case sitting on top of some conductor? How close 
together are the internal sections positioned? Anything else?

Malcolm