IGBTs are pretty fast

http://webpages.charter.net/dawill/Images/Induction719.jpg
http://webpages.charter.net/dawill/Images/Induction720.jpg
http://webpages.charter.net/dawill/Images/Induction721.jpg

Since there were no objections (..or encouragements..) to the proposed
arrangement, '719 is the bridge as I've reassembled it.

'720 is the output voltage and current waveform.  Note this is at 120-130VDC
supply, and 29kHz or so (some amount before resonance around 21kHz).

I like these transistors more than the MOSFETs in that you can see the
discrete transistion as current passes through zero; the transistor won't
conduct backwards, so the reverse drop will always be that of the co-packed
FRED.  Likewise, the forward bias is always a couple diode drops.

'721 is the rise and fall time of the output.  2.5V/ns is pretty good for
something this chunky.
On the left of this oscillograph, you can see a small dip, which I suspect
is miller capacitance.  The gate fall respectively has a small blip on it as
it passes around zero.   About 280ns after, Ic falls and Vc swings
completely in about 50ns.
When the FRED turns on, it clamps with about 10V of bounce that rings around
8MHz (t ~ 120ns), plus a lower harmonic.  This sounds reasonable compared to
the published resonance frequency of the closest bypass caps of ~10MHz.

Any objections, comments, suggested measurements/conditions before I move on
to 200V supply?

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


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