Re: Solid State Gap

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Terry,
           Nice goin'.  That's close to what I was doing with the 
MOSFET gap. I tried looking at the no quench trace but couldn't get 
thru for some reason. Did the beat envelope assume a linear of log 
shape (guess = log)?  BTW - have you tried cutting the gap off at Ip 
max (hint - interesting to test one or two old theories out there - 
watch the spikes ;)? 

Regards,
Malcolm

On 18 Mar 01, at 20:26, Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
> 
> Hi All,
> 
> I did more testing with my solid state gap tonight.  I actually have
> it hooked up to my small coil but was only running with a primary
> voltage of 50 volts so I could play with things :-))  Pictures of the
> setup are below.
> 
> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/2001-3-18/Se
> tup.jpg
> 
> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/2001-3-18/SS
> gap.jpg
> 
> As this picture shows, it works (no load on top terminal, thus the
> very long ringdown time) :-))
> 
> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/2001-3-18/Te
> k00007 .gif
> 
> The IGBT and the reverse diode seem to work perfectly well.  I looked
> at no quench and first notch quenching:
> 
> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/2001-3-18/No
> Quench .gif
> 
> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/2001-3-18/Qu
> ench.gif
> 
> I was originally thinking of just not worrying with quenching and
> shutting the IGBT of after a few hundred microseconds.  However,
> unlike regular gaps where getting first notch quenching is really
> hard, with this gap I just set the pulse width trim pot :-))  I was
> using a 3pF probe (Tek 5100) in series with a 220k Ohm resistor hooked
> to the coil's top terminal to simulate a streamer load.  The RMS
> output was 78.72Vrms with no quenching vs. 87.03Vrms with first notch
> quenching.  So that gives 10.6% more power. That 10% power is also
> going into the streamer rather than heating the IGBT which is a
> concern.  I was worried the cheap fiber optics may not run at this
> high of speed but all seems well.  I was also worried that the soft
> turn off of the IGBT would be a problem.  However, it seems that once
> the IGBT begins to turn off, it looks like too high of a resistance
> for the energy to swing back into the primary, so it's cutoff is
> actually quite effective as shown:
> 
> http://hot-streamer-dot-com/TeslaCoils/MyCoils/SolidStateCoil/2001-3-18/Te
> k00004 .gif
> 
> Even though the IGBT's cutoff is very slow, almost perfect quenching
> is still achieved.  That is an unexpected bonus!  Although, it makes
> perfect sense once one see what is going on.  The turn on time is
> excellent so not problems there.  One can even easily slow that down
> to help reduce that nasty initial pulse that causes RFI if it is still
> there with this type of gap. 
> 
> So It looks like the IGBT gap has the ability to transfer the primary
> energy into the secondary and quench very easily.  Of course, this was
> only about 50 volts with a little over 1 amp peak in the primary. 
> There is still a little way to go before I get to 13kV and 400A peak
> the small coil normally runs at...  Right now that would run about
> $650 but perhaps high voltage/current IGBTs would be cheaper once all
> the bugs are worked out.
> 
> Cheers,
> 
>  Terry
> 
> 
> 
>