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Re: [TCML] Re: Spark gap Resistance



Hi Bert and Greg,

I didn't realize 4 series gaps were used. This would certainly add to the complexity of the measurement.

I would have expected something on the order of 100V drop across the gap mainly due to a paper regarding spark gap losses using a Marx unit (Determining the Losses in Spark Gap Switches, IEEE). Although the gases (Argon, Argon/Oxygen) did change the voltage drop, it wasn't excessive. The voltage drop was quite low at about 135V for 4kV at 159kA. Spark gap resistance was much lower on the order of 0.00424 ohms. Significantly lower than Greg's 0.65 ohms. Although I do expect losses in spark gaps in an RF situation to be higher, I don't expect it to be that high.

Take care,
Bart



Bert Hickman wrote:
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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