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Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Ok, so im doing a little test on the good old CM300DY-24H half-bridge module from powerex. What i have is a half-bridge module, connected to a pair of 15mF 350VDC lytics in voltage doubler arrangement. The output goes to a tank circuit, 3uF 30kV maxwell capacitor bank, and enough inductance (coil of 2awg wire) to make the Fo = 28kHz. The gate drive is my latest work, and drives the IGBT gates to +/- 24V. The driver is pulsed at about 1.5pps, for 400uS.
The target parameter im trying to verify here is the peak current rating of these modules under DRSSTC conditions. Now, ive done some tests, but havent had a failure yet. I thought it would be fun to take guesses at what maximum peak current it will take before failure. So list your guesses here, and whoever is closest gets to boast about how 1337 they are (sorry, no real prize).
Im gonna hold off on my guess because it would bias what other people will say.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
While I'm not smart enough in the DRSSTC realm to make any educated guess, I have to ask. Are you aiming for a graceful failure (ie: open-circuit) or catastrophic failure (short circuit with explosion).
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
Hey Dan,
Well, its ZCS like usual, sine wave bounded by a exponential type envelope (classic DRSSTC primary current waveform). My thought is that the failure will probably be from desaturation. In fact, i'll say that i have already measured what i believe to be desaturation with 24Vge. This is at 3325A, still no failure.
Im very hesitant to measure voltages because my probes arent rated for the bus voltage, and i have to worry about common mode noise into the scope. A method to easily measure Vce ON would be nice, but my scope (tek TDS210) seems to get funky if you let the waveform get bigger than the screen size, so seeing a few volts on a signal thats swinging 600V is not gonna work well.
I need to build a variable supply for the gate drive so i can run it at 30Vge next and see where it plateaus.
Registered Member #146
Joined: Sun Feb 12 2006, 04:21AM
Location: Austin Tx
Posts: 1055
We have a result!
After increasing the gate drive to 30V, the IGBT exploded VIOLENTLY at 5230A, thats right FIVE THOUSAND amps. The last scope trace captured shows some signs of desaturation as the last 2 current peaks are equal in amplitude. Im still a bit shaken up after having a 1kJ explosion go off about 6 feet away.
Registered Member #1389
Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346
The biggest thing I've ever made explode was a 1N4001 by shorting 60J at 300V backwards through it. I can't even imagine the blast from 1kJ through a semiconductor, because the 60J already sounded like a gunshot and scared the krap out of me.
That being said, I can't wait to see what the aftermath is.
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Max current of a CM300, place your bets now!
