Quote:
|
Originally Posted by IrisLab
Can someone explain to me the effects/consequences of running a DC motor as a DC generator?
I'm assuming (neglecting losses) that Tw = vi = (v^2)/R = R i^2.
|
Dave,
I am guessing you are asking if mechanical power in would equal electrical power out. That assumption is correct except for the introduction of an efficiency adjustment. (Of course this only holds true for true DC brush type motors, brushless motors won't generate a voltage.) Motors are not designed for generating power in most cases so the efficiency is not optimized for generation. I am guessing 80-90% efficiency at best. Keep in mind that a lower R is translated into a greater demand on torque input. Electric trains use just such a system for braking but the motors are designed for this duty. The control system just switches in more resistance in parallel (lower R) to reduce speed. When the robot speed controllers are in the brake mode, they just short the output leads and take all the mechanical energy converted to current into the short. The back EMF generated in the motor by the high current effectively brakes the motor.