Re: Blown Cap

Tesla List wrote:
> >From jim.fosse-at-bdt-dot-comSat May 25 11:37:09 1996
> Date: Fri, 24 May 1996 06:23:23 GMT
> From: Jim Fosse <jim.fosse-at-bdt-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Blown Cap
> On Thu, 23 May 1996 21:57:13 -0600, Tesla List
> <tesla-at-poodle.pupman-dot-com>, you wrote:
> >>From dwt-at-efn-dot-orgThu May 23 21:48:19 1996
> >Date: Thu, 23 May 1996 17:53:59 -0500
> >From: David Trimmell <dwt-at-efn-dot-org>
> >To: Tesla Mail server <tesla-at-pupman-dot-com>
> >Subject: Blown Cap
> >
> >Hello fellow coilers,
> > well I can say that coiling is a learning expierience. Just yesterday
> > I blew my newly
> >made rolled cap.
> Dave,
>         Been there, done that. 3 times! I'm a stickler for learning
> curve. My first cap was a single 60mil polyethylene, oil filled,
> vacuum out gassed. Second and third, were 3 layers of 30mil
> polyethylene also oil filled and out gassed. The only one I haven't
> blown yet is my 2 layer 60mil polyethylene, but because it's only 6nf,
> I've not run it for very long.
> I decided after 3, that it was time to get in on Scott's group buy.
> I'm waiting (very impatiently) for it to arrive;)
> So far, no one has blown a CP cap. Or at least admitted to it on this
> list;)
> jim

Jim, All

The rolled amateur caps are for Neon Transformer systems and rather low 
power use (under 3KW).  Most of the problems that I have seen occur are 
when rotary gaps are used and the rep rate is taken up to levels beyond 
500 bps.  Also, the 60mil poly caps should never see more than about 
9KVAC per cap.  I have used two in series in a magnifier at 14,400 volts 
-at-2.5KW for some time (1991-1994) and they never failed.  It is important 
when series capacitors are hooked up to use about 50megs of resistance 
across each cap to help divide the voltage equally.  Once you move on to 
a pole pig or a non-shunted transformer and plan on 4 KW or more power 
output, the homegrown rolled caps are going to be stressed to beyond 
their limits.

Richard Hull, TCBOR