Re: failed cap

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

Original poster: Gregory Hunter <ghunter31014-at-yahoo-dot-com> 

Yes Phil,

It is more stressful on caps to hook them to only an
NST and a spark gap. For one thing, without the
impedance presented by the Tesla coil tank circuit,
the dv/dt goes through the roof! There's nothing to
restrain the discharge rate. Even the best commercial
poly film caps have a dv/dt limit listed on their spec
sheet, and you exceed it at your own risk. For another
thing, the cap and spark gap are still going to form a
resonant circuit with very low inductance and very
high Q! That means resonant effects can produce much
higher peak voltages and at much higher
frequencies--enough to kill a cap that might otherwise
have been sturdy enough for TC service. Probably the
best place to test a homebrew TC cap is in a working
TC.

Cheers,

--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: "philip barnes"
 > <luck_phil87-at-hotmail-dot-com>
 >
 > Hi.
 >     i built a cap with 1.6 mm or 64 mil thick PE
 > dielectric and put the
 > whole thing in canola oil. It worked great for a
 > while but while i had just
 > the cap across the nst ,,, with no tesla coil
 > connected.. to test my new
 > mulitgap sparkgap... the PE between 2 of the plates
 > broke down and now it
 > blows bubbles and hisses and only produces a spark
 > in the gap if the gap is
 > 1 mm or 30 mil . Its pretty much had it and must be
 > breaking down at 1 or 2
 > thousand volts..IS it more stressfull on a cap with
 > no tesla coil connected
 > and is it suprising my cap did not last in my
 > config. The plates are 1.75"
 > clearance from each end and 1" along the sides. !6
 > sheets of makes each layer
 >
 > Phil


=====
Gregory R. Hunter

http://hot-streamer-dot-com/greg