Re: Capacitors

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>



Tesla list wrote:
> 
> Original poster: "Steve White by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<slwhite-at-zeus.ia-dot-net>
> 
> Many things for sale hang the words "tesla coil" onto them, especially on
> E-Bay. Do careful investigation to avoid wasting money. I see a lot of pulse
> discharge caps on E-Bay which are unsuitable for tesla coil service. A lot
> of the Maxwells that I see on E-Bay are models that have a very low pulse
> discharge cycle life. If the cap only has a discharge cycle life of 100,000
> cycles it will only last about 500 seconds of total run time when used with
> a RSG at a break rate of 240 PPS. And that is only if the cap is new. They
> are almost always used with unknown service life remaining. There are some
> good deals out there but you must know what you are buying.

Life of those pulse caps depends very strongly on voltage and reversal. (as
the 7.5 power for Voltage!) It is possible that a 100,000 shot rated life
capacitor might last for 100 times as long (50,000 seconds.. still only
about 800 hours..) if run at lower voltages and reversals.  more at
http://home.earthlink-dot-net/~jimlux/hv/caplife.htm

Halving the voltage increases the life around 200 times...

Life Increase - new Max Voltage
1	1
2	0.91
5	0.81
10	0.74
20	0.67
50	0.59
100	0.54
200	0.49
500	0.44
1000	0.40


Obviously, your mileage may vary (the exponent varies depending on the
dielectric and construction.. 7.5 is for polypropylene, I think)


Also, Steve's comment about the unknown history is probably more
appropriate.  If the cap is not truly surplus (i.e. bought new as a spare,
but never used), but has been pulled on some sort of maintenance schedule
(often the case with vacuum tubes..), then a good fraction (50%?) of its
nominal life might have been used.  Pulse caps often get used in
experimental apparatus too, and who knows what happened before the
equipment was dismantled.

> 
> Steve: Coiling in Iowa
> 
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Thursday, January 24, 2002 6:52 AM
> Subject: Capacitors
> 
> > Original poster: "centauri by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <centauri010-at-attbi-dot-com>
> >
> > Hey, is it possible to run a tesla coil using only one capacitor? I found
> a
> > 15kv 2 x .0015mf "pulse discharge" capacitor. WOuld this be suitable for
> > coiling? Thanks
> >
> >
> >
> >