On-line adjustment of the torque angle for torque optimization and diagnosis purposes in anisotropics PMSM

This paper presents a torque control strategy applied to anisotropic permanent magnet synchronous machines (PMSM). The proposed method minimizes the current value in the stator phases while optimizing the motor torque. In this typical machine, torque is obtained by adding principal and reluctant torques. The former is proportional to the current value and is maximum for the electrical torque angle (phase between rotor flux and stator field axes) equal to 90 degrees. The latter depends on the square current value and is maximum for the torque angle equal to 45° or 135°. To minimize the current value with the proposed method, the torque angle is calculated with an optimizing control loop. The paper develops two solutions. The first one is available with a variable load torque for on-line adjustment of the torque angle to optimize the motor current line, and the second is a simplified solution with a constant load torque for diagnostic applications. For the two cases, experimental results are given