Some highlights (see schematic page for component info:
I used Semikron SKHI 23/12 boards for driving the gates
I used four Toshiba 200A IGBTs, each of them is a half bridge, so I have two paralleled full bridges with 400 A capacity.
A regulated current limited DC power supply was used for testing
No snubber circuit yet
On the oscilloscope you see:
top -- voltage across the AC rail. You see some nice ripple caused by the lack of snubber circuitry.
bottom -- voltage at the gate of one of the half bridges
My plans include building a robust snubber circuit (I already have all components for a RC snubber), as well as fabricating a sensible enclosure that would fit inside my welder.
As I intended, no deadtime is seen here (the bridge conducts all the time, there are no transient "dead" intervals but there are transient shorts).
I feel that this is a nice milestone in my project. I feel that I have, in principle, proven that I can get to the completion of the project. All I now need is not to f*ck anything up. To that effect, I should make a nice snubber circuit and err on the side of overbuilding that snubber. I should manufactore an enclosure that provides proper mounting, vibration protection and cooling. After that, I should make sure that front panel controls are properly installed and are protected from EMI.
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