An Effective Nontransient Active Short-Circuit Method for PMSM in Electric Vehicles

This article proposes an effective stepwise nontransient method for entering and exiting the active short circuit (ASC) of permanent magnet synchronous motor (PMSM) to protect the safety of vehicle's drive system when fatal faults occur in the electric vehicles (EV) powertrain system with high motor speed. It is found that excessive transient current and overshoot voltage inevitably occur when ASC enters and exits directly, which may cause the demagnetization of permanent magnet and failure of motor controller unit (MCU). The two-phase short circuit is utilized as a transition step before entering and exiting three-phase ASC according to the rotor magnet position, and almost no transient current and overshoot voltage exist during the whole short-circuit period. Then, there are no constraints of ASC for system design and the system material cost can be reduced. This approach is useful for function safety implement of MCU for EV application with fast attenuation rate of transient current, high robustness, and limited resources requirement. The method with effective suppression of transient current and overshoot voltage is verified by the experimental results from a 15 kW PMSM test platform.