Influence of Load Characteristics on Three-Phase Short Circuit and Demagnetization of Surface-Mounted PM Synchronous Motor

Irreversible demagnetization risk is one of the main drawbacks of permanent magnet synchronous motor (PMSM). Short circuit (SC) current is a critical reason that may cause demagnetization. In the literature, SC current w as often calculated under fixed rotor speed. However, due to the disturbance of current and electromagnetic torque under SC, the speed usually changes according to different load characteristics. Because SC current and torque heavily depend on the speed, this paper investigates the influence of load characteristics on the three-phase SC and demagnetization of a 12-slot/10-pole surface-mounted PMSM. Moreover, since the d-axis SC current is detrimental to demagnetization, the influence of load torque and inertia on the d-axis transient peak current under different loads is discussed. Furthermore, some guidelines are given for the demagnetization check when designing a surface-mounted PMSM.