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Re: need some capacitor help
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
A 9000 Vrms NST will have a peak voltage of 9000 x SQRT(2) =
12700V. That voltage will arc about 1/2 inch between sharp points in
air and maybe a little more along a surface. So if the arc over
areas are less than say 3/4 inch you might want to increase the
distance or stick some plastic in there. If you are easily arcing
longer than that, the voltage might be way to high.
If your NST is 30mA, it has a resonance at 8.8nF which should be
avoided or the voltage can resonant up way too high and damage the
caps or NST. You value is 6.8nF which "might" be close enough to do
that with the 30mA NST. In that case, you might be getting very
excessive voltages on the caps and NST. The solution there is to go
to a "LTR" cap size which as far safer:
9kV 30mA = 13.3nF
9kV 60mA = 26.5nF
Note: 1nf = 1000pF = 0.001uF
The higher load of the bigger cap will keep the voltage down to the
rating. You can add more caps in parallel if needed.
You could also set the main gap close enough that it fires there
instead of across the cap. But the best solution is more capacitance.
Try not to let it short across the cap much, the current is super
high and it might hurt the caps.
Your 20kV caps should be fine as far as voltage goes. When you get
it running be careful if they start to get too warm though.
At 12:45 PM 11/13/2006, you wrote:
This is my first coil and am having some problems with my capacitors
i have 10 20kv 680pf doorknob caps. i fitted them between 2 sheets
of 1/4 inch plexiglass and had them all hooked up in parrallell.
powering with a 9000 volt nst i had really bad sparking everywhere.
what would be my best set up with theeses caps is 20kv caps enogh or
should i put like 2 in series.
thanks for the help