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Old 01-11-2012, 01:48 PM   #5412 (permalink)
MPaulHolmes
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Location: Maricopa, AZ (sort of. Actually outside of town)
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OK, so the new controller blew up. It was my fault though. The failure was from excessive current, I believe. There were 2 issues I think:

1. I re-enable pwm in the software automatically after <= 1mS regardless of if current has gotten under control. Before shipping it, I almost disabled that feature, but you live and you learn. Normally, the overcurrent protection should never come on. But I didn't have my hardware overcurrent trip point and max software trip points set just right. I think current climbed higher and higher. The hardware overcurrent disable just slowed the climb I think.

2. Ben had an extremely sensitive throttle for some reason. In the garage testing I didn't really observe this, but it was only at 60v and less than around 120 amps. This could be due to noise on the sensor at higher power maybe. I believe the M- bar was basically an FM radio transmitter. With a low side controller like this one was, soldering the mosfets to the M- bar I think caused the oscillations on the oscilloscope that I was seeing. And it was sensing current on that bar.


The bar added some capacitance I guess to the M- signal, which was a square wave. On a high side controller, the mosfets backs are against B+, which is nice and calm. So, I'm almost done now with the final touches on new boards for a high side controller. I needed to order revisions anyway, so this should work really well I think. There will be a mounting point for M-, M+, B-, and B+! Current will be sensed on M-, which will not have much varying voltage, since M- and B- will be a single bar. M- comes in one way, you sense the current and leave as B-. It's weird, but the current coming in and the current leaving will be different. haha.

Hey! I need to change my signature.
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Last edited by MPaulHolmes; 01-11-2012 at 01:59 PM..
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