Brick test fixture

Next I needed something cheap and nasty to test one of the bricks. If it wasn't going to work, I didn't really want to spend money on a huge pile of pulse capacitors. So I bodged this up using three capacitors from microwave ovens.

Brick test fixture

The capacitors are charged off a 0-300V power supply using a DC resonant charging circuit, to get them to about 600V. Then the IGBT is fired dumping the charge into that piece of copper pipe.

Collector voltage, emitter current waveforms

The current measurement is a bit suspect. Look how it seems to begin with a sudden jump instead of rising smoothly from zero. Also see how the phase of it leads the collector voltage. That suggests the current shunt is inductive. We'll be building a proper tubular shunt soon, and cranking the voltage up to 1000V, so stay tuned...

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