This is a general motion controller question.... A couple days ago I blew up a pair of mosfets What I think happened was I had a motor going forward then switched to reverse. Basically slammed over. The motor likely developed it's full stall current of 21 amps. This blew the fuse I had on the power supply. Then I'm guessing the motor finds itself inside a powerful magnetic field and has open circuit leads and puts some large voltage across the mosfet H_bridge letting some smoke out.
I think that is the physics. basically a motor and some attached rotational mass trying to act as a generator powering a high impedance circuit. Not 100% sure I understand this well enough to calculate voltages. Question: This must be a common problem. Is it common to use some kind of diode voltage clamp to limit the volts across the controller? I've also heard of placing a reversed diode in parallel with the power supply fuse to basically sort the back EMF. What are people doing with DC brushed motors that work with currents up to a couple tens of amps? What is the maximum back EMF current? I'm guessing that a motor can only generate current up to it's stall current. Why did the motor go from full forward to full reverse? In this case it was dutifully following a hand controller but it could result from other dumb things like an error in programming I can think of all kinds of solutions but I figure some have been tested by time and are well known, -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
