Re: IGBT -- Power Switching

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Stephen Conner by way of Terry Fritz <teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>

At 16:46 21/05/03 -0600, you wrote:
>Original poster: "Jeremy Scott by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <supertux1-at-yahoo-dot-com>
>
>
>Hi all!
>
>I was scrounging around for chunk of silicon to act as
>a driver for my 120V 14A 2HP DC motor, MOSFETS would
>work but I see here that IGBT's have lower voltage
>drop between collector and emitter, which means they
>must have less 'on' resistance, and require less
>heatsinking
>etc...
>
>I guess a question is, is it feasible to use an array
>of these things a replacement for a conventional spark
>gap? I guess the tricky part would be turning them
>all on before one explodes :)

Indeed it is, this is how the Off-Line Tesla Coil (OLTC) works. It's 
basically a DC resonant charging coil with IGBTs in place of the spark gap, 
and the power supply is the line voltage rectified and smoothed (and 
preferably voltage doubled if you live in a 120V country)

The first ever OLTC was built by Terry Fritz a couple of years ago using 10 
IGBTs (see http://www.hot-streamer-dot-com/oltc/ plus various pictures 
scattered around hot-streamer-dot-com) More recently I built a mini version 
using 2 of the same IGBTs. It performed pretty well giving 13" sparks from 
a 9" tall secondary. http://www.scopeboy-dot-com/tesla/t3spec.html

With NSTs becoming rarer the OLTC will hopefully be an attractive option 
for mini/midi coils in future.

Steve C.