Re: Polyethylene Capacitors

To: tesla-at-pupman-dot-com
Subject: Re: Polyethylene Capacitors
From: James Peters <jpeters-at-enterprise.powerup-dot-com.au>
Date: Thu, 19 Sep 1996 16:45:07 +1000 (EST)
Cc: Tesla-list-subscribers-at-poodle.pupman-dot-com

On Tue, 17 Sep 1996, Tesla List wrote:

> From gowin-at-epic-1.nwscc.sea06.navy.milTue Sep 17 22:37:24 1996
> Date: Tue, 17 Sep 1996 16:50:54 -0500
> From: Dan Gowin <gowin-at-epic-1.nwscc.sea06.navy.mil>
> To: tesla-at-pupman-dot-com
> Subject: Polyethylene Capacitors
> 
> All,
> 	I`m about to build my first set of Polyethylene/Oil
> Capacitors. I've already downloaded the construction tips by
> Richard Quick and I've found them to be very complete. I've
> also purchased some 14"x50' aluminum flashing and 3-(6"x19") PVC
> pipe with caps for containers. The one question I have is,
> why should I special order some 30 mil polyethylene ( stacked
> 3 sheets for 90 mil thickness)? When 15 sheets of 6 mil polyethylene
> will do just the same. And is readily available at a department 
> store.
> 
> Big Red, HV Capacitors. Burn Baby Burn.
> ITS Member
> D. Gowin
> 

Two main reasons:

Firstly, the poly at hardware shops is usually very impure as it is only 
used for gardening etc. This leads to failure.  The good expensive stuff 
is much more pure.

Secondly, with 15 sheets you are bound to get air bubbles in the spaces 
between the sheets. This has 2 negative effects. The air bubbles are a 
good place for ozone and corona to form (destroys a cap). Also it makes 
the dielectric thicker meaning some capacitance is lost.

Greg Peters.