Tesla Forums

I was thinking of a simple ,  solid state Tesla Coil.  It would use a TRIAC in series with the 110/220 volt line. The output would go to the Tesla coil primary and capacitor. the TRIAC would be controlled by a lamp dimmer to only produce short "spikes".  These spikes, by necessity, would be on the very trailing edge of the AC input waveform. ( If at any other point  of  wave form, it would  produce  a long turn-on that would draw too much current, for one thing, and probably not allow sufficient time for resonance.) These would "strike" the LC coil, resonating it. There would be  LC protection circuit filters  on output of TRIAC to protect it, of course, and on input to filter out  "hash".  Probably cap needs to be in series to prevent excess  current draw, especially while tuning, or excess RF to TRIAC.

Advantages: Much lower  voltage Capacitor needed in Primary. Currents would be higher, so Q might have to be increased, but secondary could be same as used in another design.  Just swap primaries.. .  If you didn't want to experiment with an expensive silver mica transmitting cap, a cheaper lower voltage Mylar could be substituted. No points. No expensive, exotic  MOSFETS, though. Only One solid state device probably  needed, not 4.  Simple circuit.  No heavy  step-up transformer of Any sort. Would run straight on AC rather than require rectifiers like HexFet coils.

Disadvantages:  TRIAC have to take a lot of  hi voltage hi  current   spikes  out of phase of voltage. Might be expensive--maybe not be  surplus. Definitely use a circuit breaker or current limit choke  (Variac in series?) on input to test it!  Also, little/no isolation from line  (But, some SS designs have little, anyway.). Ground very necessary.

EDIT: Some microwave ovens use a hefty Triac. 25 A at 400 PIV. I got one for $4.25, surplus, plus shipping, on ebay. Lotsa scrapped 'mikes around, too!

I'll post a schematic when I can scan/store it (Not Very Soon!. ) TRIAC may need some high voltage divider circuit/Darlington  to  give it enough voltage to be sure of turn-on.