Problems With DRY Caps (fwd)

From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Monday, April 27, 1998 12:20 AM
To:  Tesla List
Subject:  Re: Problems With DRY Caps (fwd)

Hi Fr Tom, all,

> Date: Sun, 26 Apr 1998 12:49:40 -0400
> From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Cc: acmq-at-compuland-dot-com.br
> Subject: Problems With DRY Caps

> Perhaps others who have built "dry" capacitors and used them for a reasonable
> time would be willing to chime in here and tell us what the end results
> were.

I use home rolled dry-fired caps in a coil running at about 1.5kW but 
with a primary voltage of only 7.5 - 8kV peak. The caps are *doomed* 
to fail, BUT, we can roll them easily and cheaply (about NZ$20/cap),
we KNOW that the 15kVDC test is unnecessary (but we still do it) and 
we know that if they are run for no more than a minute per time 
(perhaps two or three firings around this length per session (time 
between sessions being defined as the time it takes for the cap to 
cool (*completely*) internally, we can get at least half an hour's 
runtime out of them and often more. I also know that the Lself is 
*very* low due to extended foil construction and the Q is not too bad 
despite the internal coronas. They stack up very well against the 
HiVolt caps I have used as an alternative. We get a measureably 
better output. The design would be excellent for lo-f apps and slow 
repetitive apps such as Marx banks (I have used it in two).