Re: [TCML] Chinese made polystyrene caps

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi DC,

Good to know. Can you explain the failure type you encountered and even 
why they might handle lower power levels? If that is true, then it may 
(or may not) be worth looking into. I'm curious if you did a postmortem 
on the cap (current? pin hole breakdown? etc..). Also, if you did happen 
to look into the caps in some detail, could you describe the end 
construction?

Take care,
Bart

DC Cox wrote:
> I've tested them.  They are not up to pole xmfr standards.  Perhaps good
> below 5 kVA, but not above.
>
> Our units are more expensive at $800, but still well below the $1,700
> Maxwell price for the same unit.  Our are actually better for TC use since
> the Q factor
> is over 20,000 as compared with only 12,000 for the Maxwells.
>
> Dr. Resonance
>
>
>
>
> On Tue, May 12, 2009 at 5:42 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:
>
>   
> > Hi David,
> >
> > Ditto on Gary and Matts' comments. This cap has come up before on the list.
> > Someones going to have to give them a try, but at $180 ea, well, someone
> > with a money tree in the backyard will have to do it. I suspect due to it's
> > small size rms currents are going to play a major role in it's limitation.
> > There is also a high probability that these Chinese caps are not up to par
> > in the derating area as is standard by major cap manufacturers. Too many
> > unknowns.
> >
> > Take care,
> > Bart
> >
> >
> > David Rieben wrote:
> >
> >     
> > > Hey guys,
> > >
> > > I was just wondering if anyone has any experience
> > > with these Chinese made capacitor types that are
> > > absolutely flooding eBay these days:
> > >
> > >
> > > http://cgi.ebay.com/30kV-0-2-F-High-Voltage-Polystyrene-capacitor-HAM-audio_W0QQitemZ360120565659QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item53d8dbbf9b&_trksid=p4634.c0.m14.l1262&_trkparms=%7C301%3A1%7C293%3A6%7C294%3A30
> > >
> > > My guess is that since this particular one is only
> > > 80 mm x 120 mm long or appr. 3 1/8" x 6" long, and yet it has a very
> > > significant energy capacity (90 J), there is no way that its internal
> > > construction could render it competant to withstand the high RMS cur-
> > > rents and tremendous peak currents encountered
> > > in larger SG driven Tesla coil circuits, even though polystyrene is a
> > > good, low loss dielectric. Likely of very fragile metallized film
> > > construction. What are
> > > your thoughts?
> > >
> > > David Rieben
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> > >
> > >
> > >
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