Tesla Forums

Hello,

Usually, a Neon Sign Transformer, Microwave Oven Transformer, or something to that effect is used as an intermediate stage between 60Hz 120 to get to 15KV or 2.5KV.

I have some powdered Iron RF Transformer Cores.  That would allow for a Solid State Tesla Coil, or a Vacuum Tube type Tesla coil to operate at resonance from a much lower voltage stage.  Now, my core can handle up to 300 volts before it arcs through the epoxy coating.  So, I would have to dip more than half of the doughnut to build up the insulation before I wound a secondary.  In all terms it's a basic toroid, and can handle 1KW of power.  This thing is 4 inches in diameter.

Since this whole thing is run at resonance, if there's 1 KW available for this stage and wound with a capacitor in parallel with the primary per say, a doorknob capacitor and a tuning capacitor to get it right on to the resonant frequency, and using this single core as a Armstrong Oscillator for a pair of power Transistors, adjusting the primary's tuning capacitor for this part of the circuit would adjust the output frequency.  The doorknob capacitor is used to get it close but to a higher frequency than the circuit will run at.  The tuning capacitor takes it down to exact.

I've used 2N2222s to produce a Class AB push pull amplifier and test the idea at a small scale.  It does mean that when you wind the transformer, that you have separate windings for a tickler circuit to feed back to the input of the transistors.  If you want it to self start, you do need to have the amplifier working at zero.  That just means that both transistors are partially on, where they'd cross zero volts.  Then background radio noise can start the oscillator.  It has to start off by amplifying something until it switches over to amplifying it's own output and feedback which will be tuned by the Parallel LC circuit on the primary.  Only one capacitor is shown.  But, in the real device there would be a tuning capacitor in parallel to hit exact resonant frequency of the primary of the Tesla coil with the output of the secondary.

In the schematic, the two inductors are really wound on the same core, and would be used to produce an output sent to the transistors bases.  I've had problems with MOSFETs and reverse conduction.  It's almost like they work as well in either direction and they don't care which is the source or drain.  They need diode support.