Re: Taming the SISG

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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.
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


Original poster: Finn Hammer <f-h@xxxx>
...
Of course I was worried that a SCR would not be
able to perform the task, but since the SIDAC´s
shouldn`t either (too high dI/dT) I gave it a go.
...
I had selected the IR 25TTS12 1200V/16A SCR for
the job, and noted that it could be triggered by
46mA @ 2Volts on the gate, so I figured that if a
gate transformer cold be made to deliver 2 volts
into a 23ohm rsistor, I`d be on the right track.
...
Cheers, Finn Hammer