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[TCML] SISG First Light

Hi All,

Well, I powered up my SISG coil for the first time today. I'm running 5 boards at the moment. As I cranked up the voltage and then variac ballast (keeping my eye on current), all was rather quiet and then ZAP! The coil threw out some hot white arcs striking an old primary coil about 5 feet away from the top load. After about 5 seconds, all went quiet again. The ballast variac was smoking! I shut it down and started looking at components (figuring I must have wired something incorrectly, rectifier died, or sisg boards took a dump).

I removed the coil and lid off of the coil cabinet and inspected the caps, bridge, and sisg. Nothing burned and no smell of anything bad. All looks brand new and none of the hv diodes are shorted. I then started looking at the control cabinet which houses my PLC, deadman circuit, voltage and current ballasts, etc. I measured the inductance of the variac ballast and found that the last time I rewired it, I had inadvertently changed the rotation direction (0 to 100%). So apparently, I started up this SISG with "no ballast for the pig". When I thought I was increasing L, I was actually lowering it. Well, I tried the coil again after all this and couldn't get anything to breakout. I could here the Sidac's firing however. It's almost as if the ballast was damaged and stealing power (it was the variac that was smoking originally).

I did get sparks and they looked great for a moment. But looks like I am in for another variac autopsy. I may first double check that nothing else is a problem by bypassing the variac (for a quick shot).

If there are other thoughts any of you might have about the incident here, please speak up. SISG's are new to me, so it's possible I'm overlooking something.

BTW, cap and primary are in series. The SISG is parallel to the power supply and before the cap and primary (as would be normal for a typical spark gap). I decided to change the wiring to this configuration (from my previous) after realizing that since I'm floating the primary, I was not limited to hookup configurations.

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