Abstract:  Interior permanent magnet synchronous motors (IPMSM) can be widely used in the transmission system of electric vehicles (EVs), which take the advantages of high output torque at low speed, high constant output power at high speed, and high efficiency. Since the magnetic field of IPMSM is designed to be saturated, which makes the output capacity of IPMSM sharply decreases in the high speed range. A method was developed to evaluate the performance of a series of IPMSM using the characteristic current and saturated stator parameters. The method takes maximum torque per Ampere (MTPA) strategy to achieve constant torque control at low speed and constant power speed ratio strategy to achieve constant power control at high speed to meet the requirement of electric vehicles, with output performance of IPMSM regulated by changing the values of the characteristic current compared with the current rates of the power module. Comparative simulation and test results using different prototypes with different parameters validate the accuracy and applicability of the method.

Key words: Interior permanent magnet synchronous motor (IPMSM), characteristic current, saturated parameters, maximum torque per Ampere (MTPA)