Tungsten Electrode Source
Subject: Tungsten Electrode Source
From: richard.quick-at-slug-dot-org (Richard Quick)
Date: Tue, 2 Jan 1996 13:46:00 GMT
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* Original msg to: Lbliao-at-alumni.caltech.edu
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Quoting lbliao <lbliao-at-ALUMNI.CALTECH.EDU>:
> Why can a high voltage transistor not be used instead of rotary
> make and break switch? Today transistors can sustain 600V with
> 5-10 nano second turnoff time, and 20-40A. They can be seriesed
> to withstand thousands of volts.
People are using power VFETs in solid state Tesla coil drivers,
but these coils are simply not able to dish out the peak powers
that the spark gap can.
With a single VFET rated to switch 600V -at- 20A you are looking at
around 12 kW peak power. By switching with a simple (and cheap)
static gap which pulses a decent capacitor, and the whole works
charged with a 12kv neon sign transformer, peak powers of 240 kW
are easily obtained in a small coil. That is a big difference.
The other problem (and I hedge this... my experience with VFETs
is very limited) is the apparent inability of these solid state
switches to handle much abuse. Coils have a tendency to "kick
back" on occasion, and I have heard from more than one source
that the solid state componets are not at all forgiving of this.
I have absolutely nothing against solid state circuits being used
to drive Tesla resonators. I am no purist who would complain that
solid state "is getting away from Tesla" and should be shunned.
But when it comes to simple bang for the buck, there is nothing
out there that comes close to the performace you get from a well
designed and engineered spark gap. Nothing.
... If all else fails... Throw another megavolt across it!
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