Online Stator Inter-Turn Short Circuit Estimation and Fault Management in Permanent Magnet Motors

This paper presents an online short circuit current amplitude estimation solution for permanent magnet synchronous motors (PMSM) with Inter-Turn Short Circuit (ITSC) fault in their stator winding. Short circuit current estimation amplitude is one of the most critical parameters while making critical decisions for the post-fault operations. Once the fault is detected, it is essential to control it to keep amplitude below rated current to prevent further winding degradation due to overheating. In this paper, a simplified ITSC fault model is developed for permanent magnet motors and integrated into the drive control for all permanent magnet motors. Based on the estimated amplitude of short circuit current, the speed reference is adjusted by an iterative scheme to bring short circuit current amplitude to a safe value. The adjusted speed reference defines the motor's Safe Operating Area (SOA) under ITSC fault. To test the efficacy and validity of the proposed method, experiments are conducted on lab prototype motors that have taps introduced in their stator windings to mimic ITSC faults.