Hi Greg,I took a day to digest what your stated. I take it that the 2700V drop was measured across the spark gap itself and not acorss the primary circuit? If so, that's a huge loss. I went to your site looking for the 4200A primary, but it shows the improved primary specs. So, I ran numbers and calc'd 13.6 ohms of primary impedance which matches your 14 ohm statement well enough. What your stating is that by increasing the primary impedance to 14 ohms from 5.3 ohms, your wall socket power draw was half of what it was. Better impedance match I guess.
That's an impressive improvement!I calc'd primary Q pretty low on your current primary (about 37). I'm still trying to figure out why the idea of high Q primary's are assumed. I think the assumption is due to the large wire or ribbon surface area and low turns. Doesn't work out that way, but I can certainly understand why it would be assumed. Maybe not so important. The primary and secondary Q's in my little window of the universe are getting rather similar.
Thanks for the numbers. Take care, Bart Greg Leyh wrote:
Hi Bart,I think that 0.65ohm accurately reflected the gap losses, or very nearly so, since the voltage and current waveforms were in phase, except that the voltage waveform was somewhat distorted relative to the sinusoidal current waveform. Still, by eye I would estimate this distortion was at no more than 10%. At 4200A the peak gap voltage drop was about 2700V.Given that the operating Zpri was 5.3ohm, one might imagine that this system would nominally work, as it did, although with considerable gap losses. The design improvements made in 1998 [increasing Zpri to 14ohm, larger toroid] actually increased the arc performance while reducing the maximum wall-plug draw down to about 25kW. The rotary gap can now operate steady-state without significant heating, as the peak currents are now only about 2500A. GLFrom: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx> Subject: Re: [TCML] Re: Spark gap Resistance To: Tesla Coil Mailing List <tesla@xxxxxxxxxx> Message-ID: <47576D54.1050304@xxxxxxxxxxxxxxxx> Content-Type: text/plain; charset=ISO-8859-1; format=flowed0.65 ohms is significant! I have to assume that 0.65 was an averaged value? It is still relatively small and I don't think reflects the gap losses associated with spark gaps. I wonder if those gap losses included the primary losses as part of the mix?Take care, Bart Lau, Gary wrote:> Actually, since power is I-squared * R, peak power in the gap is 1316 MegaWatts, or 1.3GW. But that's a peak value, for a very brief interval - good for bragging rights, but little else. The RMS current value for the duration of the gap on-time is a small fraction of the 4200A (sorry, no estimate, but <<4200A). And when you average that over a duty cycle (picking numbers out of the air) of ~ 10usec/8msec or 0.125% that the gap is actually on, you'd arrive at a more realistic figure for the amount of energy that's actually dissipated in the gap.> > Regards, Gary Lau > MA, USA >_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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