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SISG firing timing program
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
Hi Russ and All,
I made a program to look at the SISG firing timing. With this
program, the Gate resistor (100 ohm R5) can be adjusted for faster
firing if needed. For my next coil, I am dropping it to 50 ohms so
the IGBT kicks in faster. The old value of 100 ohms was a wild guess...
The file is at:
http://drsstc.com/~sisg/files/SISG-Timing-Calc-100.zip
There is a PDF file in the zip with the instructions and source code.
In general, one should try to have the IGBT TakeOver Time twice the
Main Capacitor Charge Time. That way the main timing cap is 'sure'
to be fully charged before the IGBT takes its charging current
away. The Primary TakeOver Current should be less than 100 amps too
so the SIDACs don't get too beaten up.
The SIDACs take about 124nS to get going and that time is not
significant since no real current flows, so it is ignored. The 24V
TVS has a pretty nice overshoot too (28V) that could be set in the
input file if you want. In the real world, there will be resonances,
propagation times, impedances, Emitter inductance, etc. but the
program matches the scope stuff pretty good where it counts.
It might be possible to come up with a resistor value for R5 that
would do every situation. Perhaps setting up a little Monty Carlo
thing... It is easy to mess with the program to do things like that
know. It is just the free LCC C language compiler:
http://www.cs.virginia.edu/~lcc-win32/
In general, I think having the gate resistor at 50 ohms is fine for
most stuff. 100 ohms might be a little too slow and the primary
current might get sort of high through the SIDACs.
There are more scope pics at:
http://drsstc.com/~sisg/files/BigSISGCoil/100-50OhmGate.pdf
if you like scope pics ;-)
Cheers,
Terry