RE: Thyristor driven coil ??

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Steve Conner" <steve.conner@xxxxxxxxxxx>

>Hi, just a speculative thought - has anyone ever tried (or would it work)
>to use high power thyristors to replace the spark gap in a standard TC?


This comes up every once in a while and I always give the same reply- Check
out my OLTC II

http://scopeboy.com/tesla/ol2derby/pics2.html

I looked at thyristors to start with but the di/dt was too high. I guess it
would have worked with the "interdigitated gate thyristors" that Jim Lux
mentioned, but I didn't know about those at the time. So I used some surplus
IGBTs instead. I got two "bricks" rated at 1200v, 1200A max pulsed current
and connected them in parallel.

The circuit is identical to a classic DC Tesla coil but with the IGBTs in
place of the spark gap.

By using a fat secondary coil with lots of turns, a single turn primary, and
a lot of tank capacitance (around 14-18uF @ 1000v) I got it all to work
together at 66 kHz and produce some decent sparks. The IGBTs are overrun to
at least twice their 1200A current rating but they don't seem to mind.


Steve C.