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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
If you have your snubber caps screwed directly onto the IGBT modules, then the overshoot you see is probably interference the scope picks up. This is normal in switching cricuits, as the dv/dt during transitions is extremely high and causes currents to flow through really tiny capacitances through air.
Registered Member #4992
Joined: Wed May 23 2012, 03:57PM
Location:
Posts: 108
Dark current i dont have any snubber caps mounted to my brick, i only have the bypass caps on my circuit. This is how my schematic shows it or do i need to add the snubbers also?
Registered Member #4992
Joined: Wed May 23 2012, 03:57PM
Location:
Posts: 108
I actually added a snubber 10uf 600v directly to Igbt and it made a huge difference. The ringing looks a lot less and when I crank up the volts everything sounds smoother. I was burning my tc ics everytime I tried cranking up the volts, I guess this was due to a little overshoot I hardstyle because I did not have the snubber on. The only test now is to see if I can get pass the Curie point.
Registered Member #4992
Joined: Wed May 23 2012, 03:57PM
Location:
Posts: 108
Well ive burned another igbt.It looks like the ringing isnt gone. Ive tried everything now and the problem seems to be at the 2 tc ics. Are there any of the experts that now if there is a posibility that you can get some faulty ics because i bought it from digi key.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
What frequency are you running? Igbts don't like switching fast. Probably no more than 30khz
The picture on the previous page has long wire lengths which act as antennas. You need a redesign and get everything down to a few cm of length. If you need more for the gate then you need to shield the line. Where is your inverter schematic?
Finally I like mosfets. I'd use those. As long as you have that noise on your gate you will blow chips. The signals must be perfectly clean
3 ohm resistors are too small. Try 8-10ohm on the gate. If that is not enough you can add ferrite beads . These need to be right at the gate connection on the chip
Registered Member #4992
Joined: Wed May 23 2012, 03:57PM
Location:
Posts: 108
This is my shcematic, im running at 38 khz with 10 ohm resistors and ferrite beads on the gate. I actully tried some mosfets out IRFP250 and the signal even looked worse. I dont know what else to do.
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Gate drive signal
