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A s.s. head-scratcher



Original poster: Ken or Doris Herrick <kchdlh@xxxxxxxxx>

Steve Ward et al-

This one stumps me but perhaps not someone else: I'm implementing my push-pull s.s. primary circuit, using two Powerex CM300DY-24H IGBTs. Previously it appeared to function but not satisfactorily so I've redesigned and rebuilt the drivers. Waveforms now, right at the IGBT gates, appear perfect. However... The IGBTs will conduct no current; nada, zip, neither of them. Nothing within them is shorted, per my ohmmeter, and the gate:emitter nodes are "open" per the ohmmeter.

In order to accommodate my revised driver circuit, which has back:back zener protection, I had carefully removed the 10K resistors that were protecting the gates. Was I not careful enough, do you suppose? Could the gates have actually opened up within the packages? >Both< of them?? Not hardly, I should think: they'd be shorted, if anything. Does anyone have a clue, before I have to un-mount them & jury-rig a test-setup?

Ken Herrick