Motor's work and power against the gravity

Question

Ok, I've read this answer: Why does holding something up cost energy while no work is being done?

But more questions pop up. If there is no work being done does that mean that there is also no power needed to hold object at same height?

P=A/t

If I had a rolling shutters:

Simplified by this model:

What would be the power of the pull needed to keep this weight at same height? If you want you can also think of a motor on the other side, and a rope tied with the rotor shaft. If motor has no power, obviously, the weight will pull the rope, and unwind it from the shaft. At what power should motor work to keep weight in equilibrium? Disregard mechanical loses, gear ratios, etc. I'm asking about concept.

Answer 1

There is no power associated with holding the shutter steady against the force of gravity. Power is the rate at which work is done, and no work is being done on the shutters. You could imagine using a rope to hold up the shutter. The rope would not have to continuously do work to keep the shutter from falling. It is the same with the motor. Exerting a force is NOT the same as doing work.

However, there must be a magnetic field within the motor to balance out the force of gravity, and there is work associated with maintaining that magnetic field. Electrons must move within the motor to create the field. As they move, some of their energy will be converted into heat due to the resistance of the wires. As a result work must be done to keep the electrons moving.

One more thing to note: If for some reason the motor lost power, and the shutter started falling, the shutter would do work on the motor. The energy required to do this work comes from the shutter's gravitational potential energy.