# Re: Secondary capacitance

```Original poster: "Steve Lawson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <slawson-at-basec-dot-net>

Dear Terry:

In regards to your post of (Vs) secondary output voltage, do you
believe that the secondary capacitance (Cs) should be calculated by adding
the self capacitance of the secondary along with the toroid terminal
capacitance?
In other words should Cs= Secondary self capacitance + Toroid capacitance or
should the capacitance of the toroid be ignored.
Secondly, If I'm using a 4 inch diameter coil similar to yours posted on
your website in which my NST is 15kv/60mA along with a SRSG with a break
rate of 120 BPS, can I assume that my capacitors (15 nF from Geekgroup)  are
charging fully to 15000 volts.  Does Vp indeed equal 15,000 volts ?

Sincerely,
Steve Lawson

> >From: "Tesla list" <tesla-at-pupman-dot-com>
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Secondary capacitance
> >Date: Thu, 23 May 2002 00:41:41 -0600
> >
> >Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> >
> >Hi Frederick,
> >
> >Vs = 0.7(Vp * SQRT(Cp/Cs))
> >
> >will be pretty darn close!  About 1/2 the coil's power is lost in the gap
> >which this takes into account.  For a simple equation, this is as good as
> >it gets.  You may be interested in:
> >
> >http://hot-streamer-dot-com/TeslaCoils/MyPapers/modact/modact.html
> >
> >For secondary capacitance, see this program and included notes and text
> >files...
> >
> >http://hot-streamer-dot-com/TeslaCoils/Programs/E-Tesla6.zip
> >
> >Cheers,
> >
> > Terry
> >
> >
> >At 12:16 AM 5/22/2002 +0200, you wrote:
> > >
> > >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
> > >Cs = secondary capacitance (Farads)
> > >Cp = tank capacitance (Farads)
> > >
> > >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 5½ turns
> > >1200 turns secondary, 0.3 m high
> > >6.5" by 1.8" toroid
> > >
> > >Sincerely,
> > >Fredrik Holmström
> > >
> >
> >
>
>
>
>
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>

```