Re: capacitors

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Greg,
         My experience with banks of PP caps is that they perform as 
well as any caps you could otherwise obtain. I used to roll extended 
foil caps using polyethylene sheeting (same ballpark losses as PP) 
and kitchen grade Al foil. On switching to the multi-PP caps, I got 
sparks that were a little hotter and a little longer for the same 
input power. The only significant difference between the two was a 
lack of corona in the caps (the rolled caps were dry-fired). It is 
imporant that you use plenty of strings in parallel to give high 
discharge currents with low I^2R losses in the cap as a whole.

Regards,
Malcolm

On 6 Oct 2001, at 11:28, Tesla list wrote:

> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
> 
> Hey everyone,
> 
> As most of you know, I am in the process of building a large coil (up 
> to 10 kVA). I am currently investigating capacitors. I have had it with 
> constructing oil filled rolled or plate poly caps (I've made 6) - too 
> messy, too many hours! I read with interest, some pages where people 
> have used banks (up to a couple of hundred) of commercial polypropylene 
> caps. I was wondering how well these work - are the sparks nice and 
> hot, or thin and purple? I was also after some construction guidelines -
>  most of these caps have thin leads, therefore requiring a complex 
> series/parallel arrangement to handle the current. What resistor 
> arrangement is used? How does the polypropylene stack up to LDPE as a 
> dielectric? Are these huge banks alot less efficient then a simple 
> staked plate cap?
> 
> Cheers,
> Greg Peters
> Department of Earth Sciences,
> University of Queensland
> 
> Phone: 0402 841 677
> 
> 
> 
> 
>