Re: LDPE Caps for 15kv Transformer

In a message dated 95-10-05 13:28:27 EDT, tesla-at-grendel.objinc-dot-com writes:

>Hi Coilers,
>Anybody know if 120mills ( 3mm ) of low-density polyethelene wil be
>sufficient dielectric thickness for
>a 15kv  system?
>Ive never made a rolled poly cap before, but want to get it right the first
>time, as the LDPE sheet sure
>aint' cheap ! Ime using a hospital-grade material, as the stuff at the
>hardware seemed pretty poor quality.
>It was speckled with little grains of 'crap' (????) embedded in it. (just
>asking for trouble! ) 
>My new Magnifier system will employ the series 'equidrive' system. The pair
>of series caps will use
>60mills each. I can increase the voltage on the transformer to around 17kv
>with the variacs'  overwind.
>Do you think they can handle it ? Should I change the variac tap to limit
>voltage to 15kv?
>I want these suckers to be 'bulletproof' !   :) 
>I was told that LDPE can take 500V per 1/1000 inch. Does that sound right? 


Based on my experience (and I have ruined two of these) one capacitor made
with .062 poly is good for 8 to 9 kv and no more.  A rating of 8kv should be
safe.  This means two in series should be bullet proof at 15kv.  17kv, I
don't know.  This is getting close.
Gaps set a little too wide and kickbacks cause very high voltage pulses in
the tank circuit.

Ed Sonderman