poly cap death

• To: tesla-at-pupman-dot-com
• Subject: poly cap death
• From: "Jeff Corr" <corr-at-enid-dot-com> (by way of Terry Fritz <twf-at-verinet-dot-com>)
• Date: Sat, 23 Jan 1999 10:11:39 -0700
• Approved: twf-at-verinet-dot-com

Hi all,

I posted this about a year ago, but found this paper while running
through my old tesla stuff.

I constructed a poly cap rated at 20kv, .01uF under oil.
I placed this on a tesla coil system running 15kv, 60ma, and
ran them until they passed on.  Here is what a noticed :

0:00 Start time, external temperature of PVC 72F, almost room temp.

5:15 Volume of spark gap decreases with simliar effects on spark output.
        Drops from 15" to about 7".  PVC temp 75F

13:15 Rupture of PVC sealant (RTV); small leak; PVC temp 90F

16:40 Some sort of presurized explosion taking off one endcap, spilling oil
everywhere.  Temp off scale.

16:50-30:40  The coil runs with no oil in this cap.  Noticable "burnt
poly/oil smell"

30:40 Cap failure due to arc through, probably caused by corona.

For the temperature measurements, I used a fish tank monitor, a plastic
piece
which tapes onto the outside of the glass (in this case PVC).  I use one now
on
the caps I build, allowing me to monitor their temperatures.  Usually ranges
from
70-90F.

I tried this out of curiousity and left over poly, I wouln't have expected
it to last
30 minutes anyway...

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