A semi-closed loop torque control of a buried permanent magnet motor based on a new flux weakening approach

The authors discuss the semi-closed loop torque control of buried permanent magnet motor using a flux weakening approach. Following the modeling of the motor, the power capability of the machine is briefly summarized. In the flux weakening method, the controller generates current commands so that the operating point of a motor shifts from a normal mode to a voltage-limited state and vice versa. This flux weakening approach is then extended into a torque control system, which permits almost open-loop torque control of a motor. The system utilizes an estimator, or more precisely, its alternative, for a shaft-generated torque. Some simulation results are given to verify the effectiveness of the control method. It is shown that the shaft torque follows its torque command with a certain time delay when the reference varies rapidly. In the steady state, however, the average shaft torque is well regulated to coincide with its command in spite of inadequate feedback. Other factors which affect the system performance are also discussed.<>