[TCML] Gate Drive Waveforms Ringing

["Brian" <brianv@xxxxxxxx>]

Hi Guys,

 

I have questions for the SSTC people out there, I have some ringing on my
gate drives and for the life of me I cannot seem to get rid of it. The
signal used to be as clean as can be and now it has developed a ringing that
has me totally befuddled.  I rewound the GDT and changed the IGBT so they
are all good, the GDT used to have a really nice looking waveform. I have
also changed the lead lengths going back to the control board and nothing
seems to change. I have uploaded a few images so you can see what it looked
like and what it looks like now. I have also uploaded the H-Bridge output
waveform and you can see it has a large amount of ringing at the beginning
of each transition. Also the other thing I should mention is when only 1 of
the GDT are connected the signal is very clean again, it makes no difference
which one is connected the signal is good, the moment the second GDT is
connected the ringing begins.

 

Here are the links for the waveforms:

 

The Good waveform:
http://i915.photobucket.com/albums/ac356/Brianvod/GateDrringing001.jpg

 

The waveform now:
http://i915.photobucket.com/albums/ac356/Brianvod/GateDrringing005.jpg

 

H-Bridge output waveform:
http://i915.photobucket.com/albums/ac356/Brianvod/GateDrringing004.jpg

 

I did add additional gate resistance and it helped somewhat in fact I added
until I was way over damped and it of course it began to distort the
waveform.  But anyway I am not sure why this just all of a sudden showed up,
so I thought I would post it here and see if anyone has a similar issue and
what they did to correct it.

 

Thanks Much

 

BrianV

 

 

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