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Re: Blown Rolled Cap



Quoting jim.fosse-at-bdt-dot-com (Jim Fosse):

> I just took apart my first blown cap. 1 layer of 0.060" 
> polyethylene. Identical failure!  Both look as if a sharp point
> on the edge of one of the plates punched thru the dielectric. 
> Both holes were 1.5' to 2' in from the inside of the roll.

> I had sanded and smoothed both cap's plates and used my fingers
> as roughness gages.

Having done this more than a few times on different capacitor
designs I can tell you the sharp raised points were most likely
not there when the capacitor failed. It is the energy released at
the instant of failure that distorts the plates; frequently you
will find holes blown clear through the plate, but if there was
insuffient energy to completely hole the plate, a sharp rasied
point will often be formed in the plate during the failure.

Richard Quick


... If all else fails... Throw another megavolt across it!
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