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Old 07-09-2010, 09:51 PM   #12 (permalink)
Mark Weisheimer
Join Date: Aug 2009
Location: Columbus Ohio
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Originally Posted by electrowizard View Post

I reduced the PWM to 0%.
As I disconnected my scope leads from the resistor, the mosfet died.


I'm sure stumped now. Thoughts?
Hello ElectroWizard,

I suspect that you are not done blowing parts just yet.

I think that a gate pull down resistor is in order.
Put a 10k resistor between the gate and emitter.
The very slight (perhaps 10Mohm) load of the probe
may have been enough to pull the gate low or keep
it out of the linear range a bit more. I don't
think that you are blowing the gate insulation,
I think that you are unintetionaly operating the IGBT in it's linear
region and they have VERY low tolerance to that!

I didn't notice the value of the TVS, but it should
probably limit to 15vdc as is commonly done with
15v 1W zener diodes. The TVS is a perfectly good
replacement for that if the voltage limit is similar.

When you do begin to parallel the IGBT's you will
want to match them for V(SAT) and may want to
set up a jig for doing that.

I agree with you that this stuff is a blast, and blasting a
few parts is just part of that fun!


Mark Weisheimer
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