[TCML] Re: Spark Gap Resistance

[Greg Leyh <lod@xxxxxxxxxxx>]

Hi Bert,

I hadn't considered the possibility of the circuit path inductance 
through the gaps when making the measurement, although I don't recall 
the voltage and current waveforms being significantly out of phase.  The 
total circuit path down through the front 14" rotor, across the 
electrode holders, and back up through the rear rotor is about 37", 
which could easily represent 1uH total.  The reactance of 1uH at 60kHz 
is about 0.377ohm, so the inductance could in fact have had a 
significant effect.   GL


> Hi Bart and Greg,
>
>
> I also found it very interesting that Greg saw a 2700 volt drop across the primary gap. "Short" gaps used in Tesla Coils typically drop only 150-250 volts/gap. Since Greg's primary rotary gap actually consisted of four spark gaps in series, he was measuring about 675 volts/gap. However, this included the combination of electrode resistances, gap wiring resistance, actual gap voltage drops, and the total inductance of the rotary gap. 
>
>
> I suspect that the abnormally high voltage seen across the firing gap was due, in part, to the effects of the abnormally large peak current through the electrodes (tungsten?), and the associated gap and wiring inductance. The latter might have had a disproportionate contribution to observed voltage drop due to the relatively low inductance of the remaining primary circuit and the high di/dt in the original primary circuit. It would be interesting to see what the voltage across a single spark gap might be in comparison when running at similar current levels. 
>
> Bert


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