[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] gate drive issues



Hi John,

It looks like you're seeing the superimposed combination of the gate signal and common-mode coming from the high-current primary circuit. I would suspect its an artifact of your measurement setup. Are you using a wideband CT to get an isolated gate current measurement? If so, you may be getting some induction effects from the strong primary field. Does the shape of the waveform change if you reroute the coax cable from the CT or the change the orientation of the CT relative to the primary circuit/winding? What happens if you simply place the CT in the same position with NO wire inside the core?

Bert
--
Bert Hickman
Stoneridge Engineering
http://www.capturedlightning.com
***********************************************************************
World's source for "Captured Lightning" Lichtenberg Figure sculptures,
magnetically "shrunken" coins, and scarce/out of print technical books
***********************************************************************

John Forcina wrote:
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.
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla




_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla