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Inside A Plasma Cutter (Must See Pictures for SSTCers!)

Original poster: "Jim Mitchell" <Electrontube-at-sbcglobal-dot-net> 

Hello List,

Today I opened up my Speedway 30A plasma cutter to see what sort of 
topology it used to work.  To my surprise,  I found a small IGBT brick, and 
a unusually simple driver board,  with a very small gate drive 
transformer.  Does anyone know how the brick would be driven?  As I 
couldn't find a single Gate Drive IC or any other means of gate drive on 
the board.  The brick does look small,  I believe it's a 100A 
halfbridge.  The 6 diodes you see on the edge of the heatsink are 
RURG30120, 30A 1200v.  Pictures:

Closeup of gate drive transformer, the right hand molex connector goes to 
the gates. Note bridge rectifier connections on left.
Closeup of the Brick,  sorry for the blurry picture.
Closeup of the high frequency step up transformer.
Left view of the electronics.
Top view of the electronics,  Note the current sense transformer on the 
cable going to the step up transformer.
Rear view of the Brick and heatsink.  Note the Fairchild logo on the 
Brick.  Sorry the part number is illegible,  I meant to write it down 
before I closed the case, but I forgot to.
Right view of the driver electronics,  Note the bank of 6 RUR30120 
diodes.  As well as the six blue capacitors above them.
Right view of the high voltage transformer.

Regards - Jim Mitchell