Modeling motor control

[Ether]

Originally Posted by Kevin Sevcik

Come to think of it, this explains Marshal's report of different operating characteristics between the tan and black jags. If you're running the motor at high/full speed and drop to a lower PWM command, the current will decay quicker in the tan jag, but you'll never get reverse torque, so you'll "coast" during the off cycle. In the Black Jag, there's a path for reverse current during the off cycle, so it's possible for the back emf to build up a reverse current and create reverse torque to slow the motor down quicker.

I think this makes sense, but I don't have any simulations set up at the moment to test it.

That is a reasonable hypothesis, and makes sense intuitively, but the analysis doesn't support it (unless my math or assumptions are wrong - which is certainly possible).

With a CIM and a Black Jag: even if the CIM is going at full throttle no-load, it takes almost 45 microseconds for the 2.7amp no-load current to decay to zero if you short the motor. The Jag's PWM period is 33 microseconds.