Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>For a solid state variac substitute, I have used an IGBT out of an inverter microwave run by a TL494 at 2kHz. The tricky part is that it is "inside" a bridge rectifier so that it controls AC. This is inserted between the mains and the NST. There is also a snubber of 0.1uF and 400 ohm that gets pretty hot. I haven't tuned this for long term runs yet as a lot of power is still being dumped into a 230V MOV across the IGBT. It needs more development though but does work.
http://tesladownunder.com/Solid%20State.htm#Solid%20state%20variac. Peter (Tesla downunder)
Original poster: tesla popp <teslas_lab@xxxxxxxxx> I have several small spark gap coils sitting around. None exceed 600 watts so... I, with your help, would like to design a controller for these small coils. ..... Thanks in advance for your help Coiler Forever: Jeremiah Popp