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[TCML] Question for solid-staters

Bert (et al)-

Yeah, I was thinking that that 0.4 must be unrealistic. However...my simple simulation incorporates a signal source that is independent of the secondary's Fr. I think that changing the P:S k is also changing the Fr of the secondary circuit in the process. Thus there is brought into play a mismatch between the simulation's input frequency and the secondary's Fr. In the hardware, I utilize the secondary's return-current to create the driving-current to the primary (after a 90 deg. phase-shift, amplification and pulse-burst gating, of course). That ensures a continual match between driving frequency and secondary Fr. I'm not going to bother simulating that further since I know it works, from my one successful altho insanely complicated effort a decade and more ago. We're stuck with the P:S k that we can achieve, of course, so I'm going to leave off the attempt at simulation of the k question and, when I get my 2nd driving module built, will just experiment with varying the P:P k (and the P:S, to a degree) while eyeballing the sparks.

BTW, after the expected frustration (and more) because of Murphy's Law, I've gotten my one driving module to work just fine, altho not yet with the secondary feedback activated. In 2T of 12"-diameter primary I measure >200A p-p, ~125 KHz, in 5 ms bursts at ~10/sec with only moderate warming of the 2 power transistors--& that's not yet at full input voltage. Next task is to finish the mounting-base for the primary & secondary coils, which has yet to include a small central coil-spring to receive the return-current. All the rest of the l.v. apparatus is already built & tested(and the secondary--two of them, in fact) fromprevious efforts. Then I will set the secondary in place, fire up the whole thing & see what I get from that 200A. The object will be to ultimately draw just under20A from the ~115V mains doubled & rectified, at 5ms/10-per-sec maximum spark rate, while at the same time keeping power-transistor temperature manageable. Happily, I already have enough of those $28 (!) IXFN60N80P transistors for 3 more modules--and have so far only smoked/flamed 1 of them, in my mains-doubler, a while back.

All of the above assuming, at 87, that I survive...


Re: [TCML] Question for solid-staters
Bert Hickman <bert@xxxxxxxxxxxxxxxxxxxxx>
4/24/2015 7:34 PM

Tesla Coil Mailing List <tesla@xxxxxxxxxx>

Hi Ken,

A Primary:Secondary k of 0.4 may be somewhat problematic from an insulation standpoint. It's comparable to the coupling used in magnifier driver transformers, and these can be prone to P:S flashovers with air insulation.

Try loosening the P:S coupling to 0.2 - 0.3 and extending the simulation time to 2-3 msec to allow the secondary to ring up over a longer time. You may be able to achieve similar voltage output without the need for excessively high coupling coefficients (and potentially heroic field control and insulation techniques).

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