Impact of Stator Winding of a Five-Phase Permanent-Magnet Motor on Postfault Operations

The performance of a five-phase permanent-magnet (PM) motor is analyzed under postfault conditions. Proper current control strategies are adopted so as to guarantee safe drive operation after any fault occurrence. This paper covers three fault types: the open circuit condition of a single phase, the open circuit condition of two nonadjacent phases, and the open circuit condition of two adjacent phases. Two motors with two different windings (with double and single layers, respectively) are compared under each fault type. This paper aims to highlight the difference in the motor performance of motors adopting these two different windings. A further novelty of this paper is that the proper current control strategies are derived analytically, including not only the fundamental harmonic of the flux-density distribution but also the higher harmonics. It is shown that these harmonics cause high torque oscillations. Owing to this analytical approach, the strategy can be applied to a variety of PM motors. In addition, the postfault current waveforms remain sinusoidal, making the current control easier. For each fault type, the results of both simulations and experimental tests are included. A good match between analytical predictions and experimental tests validates the proposed current control strategies.