Re: BIG solid state devices...

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

> >
> >For the IGBTs, switching time might also result in significant power
loss..
> >Rise and fall times at 500-1000 Amps look like a few microseconds.  The
data
> >sheet shows 1-2 Joule per pulse loss for 500-1000 Amps collector current.
> >At 100 kHz switching rate, thats 100-200 kW in the switching losses...
>
> They key is that we are NOT switching at 100kHz.  Were switching at 120
> BPS.  A spark gap is just a switch we turn on every 8.333mS and back off

excellent point...
But, since the bias on the devices will be reversing, does the device know
that it is staying on?  Sure, the gate drive stays hot, but, I don't know
enough about how the internals of these things work to be sure that they
don't think they should turn off when the collector bias goes away.  After
all, they are sort of like a FET driving a BJT.. when the collector bias
goes away (voltage reversal), then the base drive dissappears.. Of course,
the charge carriers probably stay in the area (after all, they DO turn off
slower than they turn on), so when the base drive comes back on, the
junction's already loaded up. Hmmm..

> you may want to see the scope pics at:
>
> http://hot-streamer-dot-com/temp/2001-04/SScap1.jpg
>
> This is just one little 1200V 150A IGBT I was running into a dead short.
> Even though I was going through all fiber optic triggering and such, the
> times are very fast and the voltages and currents are very high too.  They
> really are wonderfully well behaved for this stuff.
>

Then, there is the master oscillator - Class E power amplifier approach..
Someone at work was saying that we should take a look at that... The TC is
the tank.