'Torque motors' are rather different than most electric motors. They are specifically designed to be used at low or zero speed, and to maintain torque at zero speed (locked rotor) for indefinite periods of time.
They are essentially designed for locked rotor application.
As I recall, article 430 specifically mentions torque motors, and has specific requirements for their protection.
Don't think of this as 'going beyond code requirements for a normal motor'. Crack the book and follow the requirements for torque motors.
Depending on the specific design of the torque motor, you might get much better efficiency using a VFD, but this becomes a significant engineering project for what is probably a small motor designed to be used at 60Hz.
Edited to add: I see that 'torque motors' were not mentioned in the original post, but rather by the original poster later in the thread. My comments were directed to the use of motors designed for locked application, not ordinary motors that get locked up.
'Torque motors' are rather different than most electric motors. They are specifically designed to be used at low or zero speed, and to maintain torque at zero speed (locked rotor) for indefinite periods of time.
They are essentially designed for locked rotor application.
As I recall, article 430 specifically mentions torque motors, and has specific requirements for their protection.
Don't think of this as 'going beyond code requirements for a normal motor'. Crack the book and follow the requirements for torque motors.
Depending on the specific design of the torque motor, you might get much better efficiency using a VFD, but this becomes a significant engineering project for what is probably a small motor designed to be used at 60Hz.
Edited to add: I see that 'torque motors' were not mentioned in the original post, but rather by the original poster later in the thread. My comments were directed to the use of motors designed for locked application, not ordinary motors that get locked up.
Are these actual torque motors or GP that will be subjected to hi torque loads?
It makes no difference what the NEC says, as long as the engineer's request is greater than the minimum.
A VFD would need to be sized to the torque motor's current. The circuit would need to be sized to the input current of the VFD.
Without knowing the motor size and VFD size we cannot say which would be less.
But the OP appeared to be you were questioning if the engineer could require larger than code minimums. I went in the wrong direction.The engineer wants to go with what the NEC says
But the OP appeared to be you were questioning if the engineer could require larger than code minimums. I went in the wrong direction.
This is also the problem with simple questions to AI. Ask the question the wrong way and get results you weren't looking for.I can see that interpretation as well. Finding the right balance between NEC and engineering can be tricky.
