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*To*: tesla-at-pupman-dot-com*Subject*: Re: Secondary capacitance*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Thu, 23 May 2002 12:10:40 -0600*Resent-Date*: Thu, 23 May 2002 12:16:09 -0600*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <F_N2H.A.rI.kHT78-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "Dave Larkin by way of Terry Fritz <twftesla-at-qwest-dot-net>" <teslaman15-at-hotmail-dot-com> Hi Frederick It is also possible to roughly measure the Vout of a TC, without any fancy test gear etc. Coilers of yesteryear attempted to use output spark length as a crude guage of voltage. As we now know stepped leader effects and wildly non-uniform fields made these guestimates accurate to within an order of magnitude (or maybe worse!). However there is a method of determining output voltage from spark length which yields a far more accurate results. The coil must be operated in 'single shot' mode (ie. rather than being repetatively pulse by a fast firing spark gap, the primary cap is dscharged once.) A small DC supply is used to charge the primary cap, until the spark gap breaks down. The output spark length under these conditions _is_ (almost) a direct relation of voltage. So if a ground terminal with a large ROC (to try and make the field a bit more uniform) is used and the single shot spark length measured, one can determine the approximate output voltage, using the fact that air breaks down at ~1MV/meter for large gaps. -Dave- >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 > > > > _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn-dot-com

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