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Re: Capacitors




>Date: Mon, 23 Sep 96 14:30:34 BST
>From: Julian Green <julian-at-kbss.bt.co.uk>
>To: tesla-at-pupman-dot-com
>Subject: Re: Capacitors
>
>
[snip]
>>
>>My cap is made from 4 sheets of 10 mil each poly sheet and takes 10Kv directly
>>from the neons.   Voltage must be highter than this when used in a TC tank.
>>Don't know how much higher.  The poly in my cap does not glow.   I would have 
>>noticed this when running my cap dry.
>>
>Oops, I'm sorry if I gave the impression that my poly glowed. I was
>asking RH if a glow COULD be seen just before the cap broke down.
>If that was the case, I would surely look for it with my next cap.
>
>
Today I purchased a roll of 40lb kraft paper to experiment with. (I'm
up to 4 layers in transformer oil, it  blows at 5.9kV) I was searching
the web for information on kraft paper. After looking at the first 50
or so hits, I changed to looking for "electrical insulation". I found
this url:

http://www.sju.edu/~avanrogg/tdei/1994a/abs133.html

--- begin include ---

Optical Investigation of High-field Conduction and
Prebreakdown in a Dielectric Liquid 


C. Brosseau, A. Beroual 


Light emission studies of the high-field conduction and prebreakdown
phenomena in a mixture of mono and dibenzyltoluene
(M/DBT), used as polypropylene impregnant in the all-film capacitor
technology, have been undertaken to gain insight into the
underlying physical mechanisms responsible for these processes. The
absorption spectrum of this fluid, in the UV region, shows
the appearance of structured bands at 348, 366 and 386 nm indicating a
luminescence process via anthracene and
9-methylanthracene impurities at a concentration of 3\xtenp{-3} mol/l.
Optical and electrical measurements were performed
simultaneously on the electrically stressed fluid. Electroluminescence
of the impurities contained in M/DBT has been investigated
using a new uniform field electrode arrangement. The light inception
stress was determined to be $\sim 20$ V$\mu$m\pwr{-1}
for ac excitation (50 Hz).

---- here it is;) --->
 Configurations with different interfacial situations were studied and
we have evidenced a correlation
between charge injection and electroluminescence activity.
--- end include ---

They DO GLOW just before they break down;)

	jim

p.s. I'll bet you need a photomultiplier to see it though;(