PROBLEM WITH IPMSM TORQUE CONTROL

Sir, I am working on torque control of IPMSM with MTPA and Field weakening and also referred matlab example file. Now my questions are

1. Why Speed input is given to the shaft of the motor rather than torque as we do in speed control?
2. If speed is the input given via a dyno by coupling, then why not the self speed of the motor when supplying collide with the speed input?

Kindly clarify my confusion.

My sincere thanks in advance

Answer 1

[Dakai Hu]

Hello,

I believe the 2 questions you asked are esentially the same question.

Generally speaking, there are 2 control mode in motor control applications: speed or torque.

In speed control mode, you'll have to design a speed control loop and torque is given as load to the shaft of the motor. In this mode you cannot specifiy the exact amount of torque generated by the motor - it is all up to the load torque and the governing mechanical equation.

In torque control mode, you design a torque loop ( most likely an open loop) and from which accurate torque control is possible. Speed of the motor will again have to be determined by load, but this time on a test bench we use the coupling motor as a constant speed source. Of course you can leave the motor uncoupled and freely accelerate, but that free acceleration would be out of control if you output a high torque.