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Re: Resonant cap?
Original poster: "resonance" <resonance@xxxxxxxxxxxx>
Some experimenters use 1.6 x Cres value. I prefer 1.3 x Cres value
for all my nst powered coils. The extra current makes the spark
dance around more on the toroid and it looks more interesting. 1.6 x
Cres will actually give you the longest possible spark but it's a
strict capacitive type discharge and usually a single streamer where
the 1.3 x Cres value makes multiple streamers of purple off the
toroid and usually at 2-3 different discharge points. Less spark
channel current but a lot more activity. The sparks rotate and seem
to have an "it's alive!" type character. It's more of an art thing
vs a long single streamer --- your choice.
For your 30KHz transformer, the formulas that you want are these:
Zout = Vs_oc_rms/Is_sc_rms
Cres (nf) = 10^9 / (2*pi*freq*Zout)
use 30KHz for your frequency. The assumption here is that the
winding resistance is insignificant compared to the current limiting
leakage reactance. If you can measure the primary and secondary
winding resistance, we can verify the assumption.