[TCML] SISG - now with a "real" pig coil

[FIFTYGUY@xxxxxxx]

Folks-
 
    Last night I finally got around to running the SISG  on my 12" secondary 
"pig" coil. Previously I had reported on running the  SISG on a 6" coil, but 
with a 10kVA pig. That coil was a bit small for the  power. 
 
    I only ran for about 30 seconds before I saw a  flash from the 
electronics under the primary and the coil quit working. Once  again, a section of one 
of the rectifier legs blew out (diodes vaporized, the  string in several 
pieces).
 
    After investigating today, I found that during that  brief run one of the 
SISG boards was damaged. One SIDAC vaporized, its two  brethren cracked, and 
the IGBT in that section shorted as well. Although the  IGBT has 10 ohms of DC 
resistance from gate to C and E, the collector and  emitter are a dead short. 
The SIDACS explode, but you can't tell a dead IGBT  without a meter.
 
    FWIW, I'm still running the same .220 uF total  primary tank. Calculated 
~55 uH of primary, 50kHz Fres calc and measured. Pig  ballasted to 60A max, 
variac'ed for 280V out. I didn't crank the  variacs past where the gap fired 
rhythmically, since I'm running STR and I  didn't want the BPS to run away (easy 
with a SISG). Six SISG-4 boards for 21.6kV  firing point.
 
    I had just finished doing some runs with the same  setup with the RSG. I 
had just finished my "Terry Filter" for the pig earlier  that day, and it 
appeared to eliminate much of the kickback I was having to the  control panel. I 
simply removed the ARSG and installed the SISG and  rectifier.
 
    Based on my experience so far, I wouldn't push the  IRGPS60B120KDP  IGBTs 
past 5kVA.  The instantaneous currents  seem to cause damage very quickly. 
All my previous caveats about high-powered  SISG coils still apply as well. 
 
    FWIW I was getting 10'+ sparks from it before it  died, around 10kVA 
input (based on the panel volt and ammeters for the pig  input). I haven't 
bothered fine-tuning the coil yet, as I'm working on other  issues.
 
-Phil LaBudde
Center for the Advanced Study of Ballistic  Improbabilities



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