[TCML] gate drive issues

[John Forcina <forcijo10@xxxxxxxxx>]

Hey guys, so i am nearing completion on a new large CM600 based DRSSTC and
i am encountering this strange problem that i just cant wrap my head
around.  I suspect that i could have partially damaged igbt's however i am
hoping that is not the case.   I am experiencing a very strange problem
with my gate drive waveforms.  As i increase my bus voltage the gate drive
waveforms seem to get worse and worse and it seems to be directly
proportional to primary current although they look pretty nasty to begin
with.  Here is a scope capture of primary current vs the waveforms of one
of the gates.
https://secure.flickr.com/photos/forcijo/8034549201/in/photostream  Here is
a similar capture that shows primary GDT waveforms vs the waveforms at one
of the gates
https://secure.flickr.com/photos/forcijo/8034549201/in/photostream

This whole situation gets worse and worse the more i crank up the bus
voltage but strangely i am still getting pretty good output waveforms
https://secure.flickr.com/photos/forcijo/8034761102/in/photostream/ aside
from the initial cycle which has some weird oscillations going on
https://secure.flickr.com/photos/forcijo/8034764783/in/photostream/  Yet
another oddity is when i synthesize feedback from a signal generator (when
there is no actual current flowing through the system) all the waveforms
look quite alright.  This is another thing that makes me suspect they are
they igbt's themselves but i am pretty stumped.  If anybody has any ideas
of what the problem is i am experiencing that would be greatly appreciated.

John.
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