RE: [TCML] Very High Voltage Polystyrene Caps on e-bay

["Lau, Gary" <Gary.Lau@xxxxxx>]

Oh, I hadn't noticed the screw terminations!  That does paint a more favorable picture.

Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of bartb
> Sent: Thursday, September 04, 2008 11:08 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Very High Voltage Polystyrene Caps on e-bay
>
> Gary, in this case the terminations are interesting (as if a screw is
> inserted on these caps in their end plates). Looks like the end caps are
> thread nuts of a sort. Promising from that view.
>
> And from a "puny" view, I have to tell you that I have been using
> polystyrene caps for 10 years now with no warmth, failure, or even
> performance degradation. But my caps are 20nF, 60kV, and maybe a bit
> special. The caps are cylinder shaped and 3" diameter x 16.5"L with a
> huge 3/8" brass threaded rod protruding about 1.5" out of each end. Even
> the nuts are silver plated. These were made by CSI (I have 3 of them).
> So nothing puny there as their obviously built for high current.
>
> It's the mechanical internal construction that is really in question
> with the caps Greg listed. I did note that some of the other caps the
> seller had were similar, but those had leads as part of the
> construction. However, the cap Greg listed were like threaded inserts at
> each end. The leads would probably be fine, but it was interesting to
> see no leads on this particular cap.
>
> Bart
>
> Lau, Gary wrote:
> > I agree with everything that Bart said.  But, all of the polystyrene caps that I gave
> seen (I have not looked extensively) have had very puny end terminations.  I think
> that polystyrene caps are mainly used tor temperature stability, as opposed to high
> current capability.
> >
> > Regards, Gary Lau
> > MA, USA
> >
> >
> >> -----Original Message-----
> >> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> >> Behalf Of bartb
> >> Sent: Thursday, September 04, 2008 9:21 PM
> >> To: Tesla Coil Mailing List
> >> Subject: Re: [TCML] Very High Voltage Polystyrene Caps on e-bay
> >>
> >> Hi Greg,
> >>
> >> Yes, polystyrene is excellent for high frequency pulse caps. These caps
> >> might be ok, but they are an unknown and a risk until some tries them
> >> and reports back. There's no telling what the internal end construction
> >> is like. The power dissipation is my biggest worry (it is a rather small
> >> cap, so the power cannot be distributed across a string as it could with
> >> say 15 of the CD 0.15uF caps needed to achieve the same value). There
> >> are some unknowns, but nothing really stands out as a show stopper,
> >> expect maybe the price (a string of CD caps to make the same value would
> >> cost less). So price and the fact that it's an unknown is the risk. The
> >> dielectric itself fine.
> >>
> >> Bart
> >>
> >>
> >> G Hunter wrote:
> >>
> >>> There's a whole page of these oddballs on e-bay of various sizes and voltage
> >>>
> >> ratings:
> >>
> >>> http://cgi.ebay.com/50kV-10nF-High-Voltage-Polystyrene-capacitor-HAM-
> >>>
> >>
> audio_W0QQitemZ150269299882QQcmdZViewItem?hash=item150269299882&_t
> >>
> rkparms=72%3A552%7C39%3A1%7C66%3A2%7C65%3A12%7C240%3A1318&_
> >> trksid=p3286.c0.m14
> >>
> >>> Polystyrene is one of the "good" pulse cap dielectrics, right?  I wonder if one of
> >>>
> >> these might be suitabe for a tabletop TC?  Anybody ever tried one?  If not pulse
> >> duty, then what are these good for?
> >>
> >>> Greg
> >>>
> >>>
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