Re: LDPE source and thickness

To: tesla-at-pupman-dot-com
Subject: Re: LDPE source and thickness
From: Hollmike-at-aol-dot-com (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Sun, 28 Mar 1999 11:39:31 -0700
Approved: twf-at-verinet-dot-com

In a message dated 3/28/99 3:54:19 AM Mountain Standard Time, tesla-at-pupman-dot-com
writes:

> But I read somewhere that LDPE would resist 1200V/MIL, which means that a
>  62.5MIL sheet would resist a 75000 V tension. My xformer is rated
12KV/30ma.
>  Can I use the 1/16''-thick sheet for my caps??? And what do you use a
vacuum
>  pump for in the building of a rolled cap???
>  
>  Thank you for your help
>  Sam
>  
Sam,
    I believe that PE will withstand 1000VDC/mil.  You should derate it for AC
use to 300VAC/mil, which would then be 18.75kV.  That will probably do ok for
your 12kV neon, although it would be better if you put two caps in series to
be sure.  Your caps could see as much as 24kV peaks during operation.  Most
agree that the voltage that any home brew cap should be limited to about 5 -
6kV to prevent corona formation and make the caps "bullet proof".  Two caps in
series made from the 1/16" PE should be fine with your power supply.  
    The vacuum pump is used to remove trapped air bubbles from between the
plates and dielectrics.  If you do not remove these air bubbles, corona will
surely form and destroy the PE over time.  It might be even better if you can
fill the container while the vacuum is applied and fill it very slowly.  This
would help prevent air from being trapped during the filling.
 Mike