Originally Posted by
Dave H
The direct relationship previously suggested is only true at stall.
The relationship is valid at all speeds. Torque in a permanent magnet DC motor is directly proportional to current. The current is inversely proportional to resistance. At any given speed, reducing the resistance will increase the torque and power in inverse proportion to the change in resistance.
There is a small deviation in this behavior, in that some amount of current is always necessary to operate the motor, even with no load. This is due to frictional and hysteresis losses. For the purposes of our conversation they can be ignored.
Originally Posted by
Dave H
The inductance becomes more important as RPM increases, quickly becomes far more important than resistance.
The inductance affects the commutation timing required for optimum operation. Inductance has much less effect than resistance on output power, since it is reactive, and therefore lossless.