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Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I don't understand. I have tried a few different chips. The latest are the HGTG40N60A and the FGH75N60SFTU. They work fine up to about 40A rms. At this point, despite my cooling fans (103cfm) they are getting warm. When I hit 45A they go.
So, I figure if I run two in parallel I should be fine. When I run them at 20A I have no problems. So, I run two in parallel on separate heat sinks, each with their own fan. Strangely, when I hit the same current they go. I am also looking at the Vpeaktopeak, and it seems to be under the 600v maximum for the IGBTs. I tried a 1200v IGBT, but this one heats up quicker than the 600v models.
My gate voltage is +/- 15v, so I don't think this is an issue.
I am thinking about trying some mosfets again.
Any thoughts? Could it be that it is the voltage that is destroying the chips and not the current? If this is the case, any suggestions?
EDIT:
I decided to probe my gate voltages again. Most of the time it is a clean square wave +/- 17v. However, as I get to higher currents there are sharp spikes at the transition points that peak over +/-30-35v. I am sure this can destroy the chip as the ones I am using have gate maximums of +/-20v and +/-30v.
The question is now how to I damp out the voltage spikes? Would some zener clamps be able to catch such a transient event?
Registered Member #235
Joined: Wed Feb 22 2006, 04:59PM
Location:
Posts: 80
I are you positive you have no cross conduction? IGBTs have a much longer Tdoff than Tdon, therfore I don't think you can drive a bridge with 50% duty cycle gate waveforms.
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One IGBT blown after another...help
