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Re: Arc length vs pwr



Mark,
      You wrote in reply....
> >
> >Well that happens on each half cycle of primary ringdown during 
> >energy transfer to the secondary. But bearing in mind that unless
> >there is an external source of energy from somewhere, Vcp can not
> >rise higher than it initially was before the gap fired can it?
> >A cap with high ESR will suffer badly from running in an uncoupled 
> >circuit as the dielectric heats and possibly hot-spots.
> >
> >Malcolm 
> >
>      Malcom,
> 
>  The voltage most certainly can rise above the source, if
> the primary circuit is viewed from "inside" the loop 
> I.E. the capacitor, coil and closed spark gap, the voltage acrossed each
> reactance is proportionate to the
> current through it. This is series resonance and current is maximum, if
> the capacitor has a reactance of lets say
> 10 ohms and the inductance also 10 ohms (resonance) the
> two reactances are of opposite signs so together they
> cancel leaving only R losses and the resistance of the
> spark gap to limit the discharge current. If the total
> non-reactive resistance of the circuit is lets say 5 ohms
> (gap and wiring losses) the peak discharge current could
> be as high as 2000 amps, now if this 2000 amps is flowing
> through our primary capacitor the drop acrossed it could reach 20000
> volts with a 10000 volt source. Once that
> spark gap fires the charging transformer has nothing to
> do wth nothing. I wrote a short article in the TCBA news
> a few years back that explains it a little better than I
> can go into here, (TCBA news Vol 12, #4 pg. 14-16).

I'm going to have to disagree but I will measure it to see whether I 
am wrong or not. I appreciate what you're saying, but you are not 
feeding your series circuit with an external voltage source. The 
capacitor _is_ the energy source and can only lose it from there, at
least that is what the scope says. Have you actually _measured_ the
voltage as climbing above what you initially charged the cap to? Once 
again, E=0.5CV^2. Where does the energy come from that allows the cap 
to go higher than it was initially?
     This consideration does not apply to the safety gap unless the 
safety gap is bridging the capacitor itself since the safety gap 
normally bridges rather low value stray capacitances.

Regards,
Malcolm