Research On A Semi-12-phase Fault-tolerant Permanent Magnet Synchronous Machine Used For Electric Vehicles

Increasing attentions on safe and high-reliability operation of AC machines intraction applications have intensified efforts to investigate multiphase fault-tolerantdrives and its control strategies. The six-phase PMSM is often considered as anexcellent candidate for high-performance and high fault-tolerant capability. Thispaper deals with a fault-tolerant semi-12-phase permanent-magnet synchronousmachine (PMSM) used for wheel-driving electric vehicle applications.High iron loss and temperature rise of permanent magnets (PMs) due toexcessive magnetomotive force (MMF) harmonic components are the maindrawbacks for PMSM equipped with FSCWs, especially in high-speed operation. Inthis paper, all-teeth-wound FSCW is employed, and the improved windingdisposition changes the winding factor of each harmonic component to suppressair-gap MMF harmonic components. Besides, the electromagnetic design of a24-slot/22-pole semi-12-phase PMSM is presented.The current induced in short-circuited coil of a distributed overlapped-windinginduction machine can be limited to nearly zero by canceling the flux that passesthrough the short-circuited coil, which is impossible for PMSM equipped withFSCWs. Therefore, the only way to limit short-circuit current (SCC) is to possess alarge leakage inductance. An analytical method that calculates the slot leakageinductance of stator with all-teeth-wound FSCWs is proposed. Additionally, thefault-tolerant control strategy of winding short-circuited fault is deduced andvalidated based on finite element analysis.The semi-12-phase PMSM is potentially fault tolerant due to its additionaldegrees of freedom. The fault-tolerant control strategy presented in this paper limitsthe amplitude of the exciting current to rated value, and a circular rotating field isachieved by regulating the phase angle of the exciting current in the remainingphases. The fault-tolerant control strategies in each faulty mode are investigated.The flux-weakening capability of the proposed machine is investigated in this paper based on the comparison of three configurations. Besides, the salient poleeffect in phase-deficiency operation mode is analyzed.