A Universal Maximum Torque per Ampere Method for Permanent Magnet Synchronous Machines

Considering the advantage of minimizing current magnitude, it is necessary to develop an effective maximum torque per ampere (MTPA) method for an interior permanent magnet synchronous motor (IPMSM). This paper proposes a universal MTPA method for permanent magnet synchronous machine (PMSM) drives. By analyzing the relationship between the electromagnetic torque and current vector angle, the optimal angle corresponding to MTPA can be derived, which is a function of torque with gain. The gain is related to the machine parameters. However, the product of the torque and the gain is within a certain range for a large class of PMSMs. As a result, the optimal MTPA angle for the current vector can be obtained using curve fitting method and the derived expression is universal. The proposed MTPA angle curve is suitable for IPMSM and SPMSM, and it works well in the situation where the saturation of q-axis inductance happens. Simulation results are presented to validate the effectiveness of the proposed method.