Re: MMC Caps

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

Original poster: "Sean Taylor by way of Terry Fritz <twftesla-at-qwest-dot-net>" <taylorss-at-rose-hulman.edu>

Hi Rob,

> I've got 3 NSTs, each 15kv 30ma. So for 15kv 90ma the resonant tank cap
> would be 0.0159uF. In theory, one string of 10 of these caps should do it.
> The actual capacitance would be .0150 and should take 10 caps * 2kv = 20kv

You really are pushing the limit of the caps . . . especially since the peak
voltage of your NST bank is going to be about 21.2 kV (sqrt(2)*15).  The
caps will handle higher than 2 kV, BUT, if you use just 10 of them, you'll
be very close to running resonantly (almost exactly), so incredibly high
voltages are possible should the gap not fire, or something come
disconnected.  I would go for 2 strings of 13, more $ I know, but it would
put you into LTR, so you wouldn't get the resonant rise, you would have a
higher RMS and peak current capability, and they will probably last a lot
longer.
You could also just use 2 of your NSTs with a single string of 10, which
would make the system LTR, and you wouldn't get the resonant rise.  The caps
would also load down the NST so you wouldn't get the full peak voltage
stressing the caps every cycle.  That may be an option if you don't want to
spend extra on caps . . .
If you want to go for the 1 string of 10 and all 3 NSTs, you can try it,
they'll probably hold up for a while (Terry probably has a better idea of
that), especially if you're careful!  That's just my opinion, I'm sure
you'llget plenty more :-)

Sean Taylor