# Secondary capacitance

```Original poster: "=?iso-8859-1?Q?=22Fredrik_Holmstr=F6m=22?= by way of Terry Fritz <twftesla-at-qwest-dot-net>" <osis-at-telia-dot-com>

Hello all,

I'm trying to calculate the peak secondary voltage using this formula:

Vs = Vp * SQRT(Cp/Cs)

Vs = peak secondary voltage
Vp = peak charge voltage of tank cap

How do I find out the secondary capacitance (Ctot = Csec+Cterm)?
Or more exact, how do I calculate Csec (sec. coil capacitance)?
Using Bert Pool's formula for toroid capacitance, I calculated a Cterm
value of 2,503 pF.
Is the capacitance of the secondary coil significant?

Using the first mentioned formula, my 8kV input and my 0,01 uF tank cap
gives about 715 kV peak secondary voltage which (even under ideal
conditions) seems a little high for my small coil.

I wouldn't know what to "expect" from my coil. Here are the specs:

Dual 4kV parallel NSTs phased for 8kV
0.01 uF MMC
Single static gap
Flat primary tapped at about 5˝ turns
1200 turns secondary, 0.3 m high
6.5" by 1.8" toroid

Sincerely,
Fredrik Holmström

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