Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

Have you tried an RC snubber? I'm trying that on a new driver board.

[DJBecker]

Originally Posted by jackbauer

Looks like the VLA is driving my gate off too fast. Common problem at my age i'm told

You put all of that effort into a fast, high current gate drive only to find that you need to slow it down.

What you want is a gate drive that operates at full gate current until the controlled voltage starts to rise, then drops to a low power mode. That way the device goes through the high power dissipation regime at maximum switching speed, but slows down at the end. Ideally you want to be just slightly under-damped (not critically damped) with a slight voltage bump.

I've seen discrete circuits that do this by shutting off the gate drive when the voltage starts to rise, using the propagation delay to match the remainder of the rise time. But I haven't see a gate driver IC that does this, or anything more sophisticated than "pulse mode".

[jackbauer]

Some good news. Upped to 24v bus and larger load inductors. At 200amps the spike was +20v above the bus. Went for it and upped the gate resistors from 3r3 to 33r. Big improvement. Spike now only +3v above bus at 200amps with resultant miller knees. Time to start playing with resistors and schottkys.

i have a theory. The newer powerex cm400 modules i'm using here are much faster than the fujis i used in the car. So if they turn off faster than necessary it causes problems for this application rather than solves them. So if the switch goes off faster than than the diode can come on = problems. Need to find a balance ...

[jackbauer]

Well , just in case anyone had doubts , the controller really does pump 500amps

http://www.youtube.com/watch?v=8HtwO9Q1Vjk

[jackbauer]

Held the controller at 500amps for 7 minutes this evening.

http://www.youtube.com/watch?v=eL1Jxw9aCio

[MPaulHolmes]

T minus 30 seconds

[MPaulHolmes]

Originally Posted by jackbauer

Held the controller at 500amps for 7 minutes this evening.

That's what you call 500 amps continuous.

[jackbauer]

Originally Posted by MPaulHolmes

T minus 30 seconds

Sad day

[harlequin2]

Love ya work jackbauer!

[jackbauer]

Here's some pics for ya Notice the nice relaxed turn off and no spike. Whats a few nano seconds amongst friends?

Held 500amps for 15 minutes today with a brick on the accelerator. Makes pikes peak look like a speedbump. Coolant topped out at 40c on the heatsink. Melted some wires on the inductor bank and boiled a gallon of water.