This question is a follow up to the question I had asked on electric torque of DC motors
I've done my research but couldn't find a satisfactory answer. I would appreciate if the answer was told with a fundamental concept to it.
Shown in the figure is a simple pulley system with a weight attached to it. The centre of the pulley (of radius, say R) is connected to the output shaft of the PMDC motor.
When I switch on the supply, the motor starts to rotate and produces a torque called the driving torque. The weight attached also produces it's own torque because it's a force acting at radial distance. Let this torque be the load torque.
My teacher says that as the pulley rotates at constant velocity, the torque produced by the motor = the torque due to the load (as there is no acceleration).
My question is this: if the torque due to the weight = the torque due to the motor, shouldn't the weight be stationary? How does it move up? Obviously the torque due to the motor has to be greater than the torque due to the weight to lift it off the ground right?
Moreover, how does the motor draw the right amount of current, thereby maintaining constant torque to keep the velocity constant? How does it not accelerate the weight by producing more torque than the load?