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Re: Taming the SISG



Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

The SCR's were wired to act as diodes by using a diode from the gate to the anode. Not something one would normally do but I had more silicon acreage as SCR's which I found in the dirt in a junk yard. Still 12.5kA is more than most people push through a semiconductor : ) I agree that lack of clamping pressure may well have been a limiting problem.
Diode arrangement explained here.
http://www.allaboutcircuits.com/vol_3/chpt_7/5.html
Your video shows it has quite a different pulsating sound. Is that beating with mains frequency?
Peter

Original poster: Finn Hammer <f-h@xxxx>

Tesla list skrev:
Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>
Nice work Finn.
It may not be important in this setup but the 46mA 2V trigger is a bit like driving an IGBT gate with 3 V rather than 30V.

This is what I thought, and the reason that I am
more than thrilled that it worked out.

Unfortunately I don`t understand your gate
arrangement in the links, but lack of clamping
pressure looks like a good reason in my wiew.

Cheers, Finn  Hammer
I did some SCR stuff with hockey puck SCR's to catch reverse EMF from a can crusher by wiring them as diodes. I was able to pass 12.5kA in this way. Eventually blew at 15kA but my voltage sharing in the stack was not well thought out. Peak allowable current for a similar puck is 150A into the gate. I never got to measure it but gate current will rise progressively with applied voltage until the SCR conducts in this setup and will tend to force rapid conduction. Certainly on the CRO the turn on in a diode setup was very rapid at least at low currents and seemingly much faster than might be expected from a big SCR and I seem to recall seeing little overshoot even at microsecond timeframes.
http://tesladownunder.com/CancrusherSCR.JPG
http://tesladownunder.com/CancrushSCRbank.jpg
http://tesladownunder.com/CanCrushing.htm#Can%20crusher%202
Peter
Th