Subject: Re: Bubbles
Date: Fri, 13 Jun 1997 07:57:38 +1200
From: Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
> I have read many references in this list about failure of capacitors due
> air bubbles. I am currently making a flat plate capacitor of 0.015uF.
> using Polystyrene Sheet (80 mil thick), and sticking aluminium foil to
> with insulating varnish.
> Because I know I have air bubbles what can I
> expect the failure mode to be? I expect the breakdown voltage to be
> 40Kv so should be ok with by 10KV 50ma Neon transformer.
Speaking from experience with run-in-air LDPE rolled caps, main thing
is heating at any favourable corona spots (foil edges) wnich seems
to actually "crack" or decompose the plastic. Shortly before the caps
that I described in that article fail, the sheeting inside them is
noticeably oily and has a strange pong to it. Appears the plastic
degrades to the point where a spark eventually punches through.
> Also are their any other coilers in the UK, I don't see much UK
I have a good friend in the UK (Richard Craven) who has just got
himself set up with proper Web access and says he will rejoin the