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Re: Capacitor



Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Leo,

Larger than resonant (LTR) capacitance is a good thing,
especially for NST powered coils and even more so for
NST powered coils that are equipped with a synchronous
rotary spark gap (SRSG). However, there are limitations
to this and .44 uFd is WAYYY too large of a primary ca-
pacitor for a 15/60 NST powered coil. I believe around
.02 uFd is a resonant capacitoance for a 15/60 NST trans-
former and 2x resonant size is considered optional for a
stationary gapped NST powered coil and 3x resonant
for an SRSG NST coil. So with your stationary gap,
.04 uFd would be about as big as you would want to go
with your coil. Your capacitor is about 11x too large and
even if you were to series the 2 caps instead of paralleling
them, you'd still be at .11 uFd which would still be nearly
3x to large! You should probably opt for the Cornell-Dubilier
942 series snubber capacitors (.1 or .15 uFd each at 2000 volts) and series-parallel how ever many you need to get the
correct total capacitance with a multiple-mini capacitor (MMC).

Also, I believe you'd be better off to take out your rectifier and just run AC with this type of coil. DC
powered coils require proper filtering or else you're
just running a half chopped off sine wave instead of true DC and this would not be an efficient way to
operate the coil.

I would also consider building a better multiple
section stationary spark gap with forced air cooling
to aid in quenching or if you're willing to take on an
additional constructional challenge, go for a SRSG.

David Rieben


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, June 27, 2006 12:35 PM
Subject: Capacitor


Original poster: "Hajdrowski, Leo T." <leo.hajdrowski@xxxxxxx>
Hi All,
One quick question.
I just finished helping my son build a coil:
15 kv, 60 ma nst with full wave rectification
Secondary 10.5" x 30" #22GA wire
Primary 3/8" 10 turns copper tubing flat coil - 1/2" spacing between
winds
1" spacing between primary and secondary
First windings of secondary approximately 1" above primary.
Stationary spark gap with 1/4" spacing
20 amp variac
30" dia. Torroid
(2) .22uf 90KV capacitors in parallel (They came from an X-Ray machine
and are about 4" dia. X 18" long).
We only get about an 8" spark and no corona.....it doesn't appear to be
high frequency, more like a step-up xfmr.
Is too much capacitance bad?
Thanks...Leo