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Multi-phase permanent-magnet (PM) motor is a competitive candidate for application where uninterrupted operation is demanded under fault condition. However, double-phase open-circuit or short-circuit faults result in serious problems, such as high fluctuating-torque, deteriorated dynamic performance, even breakdown. This paper proposes a novel unified decoupling vector control strategy to restrain torque fluctuations and improve dynamic performance for a five-phase PM motor with arbitrary double-phase failures. The novelty of the proposed strategy is the development of reduced-order orthogonal transformation matrices and remedies voltages, and then the smooth operation with vector control strategy can be achieved under double-phase open-circuit or short-circuit fault condition. The decoupled motor model in the synchronous rotating frame is achieved by the combination of the reduced-order orthogonal transformation matrices deduced from the optimal fault-tolerant currents and the remedy voltages. The torque fluctuations cancellation is achieved by the remedy voltages. This control strategy exhibits the improved dynamic performance with smooth torque of the faulty PM motor. The experimental results are presented to verify the feasibility of the proposed strategy.

In recent years, permanent magnet vernier (PMV) machines have been attracting more and more attention due to the inherently exhibited advantages such as high torque density and simple mechanical structure. In this paper, a consequent pole (CP) PMV machine with single-layer concentrated winding is proposed. The novelty is that the asymmetric air-gap field distribution is introduced to improve its working harmonics and to reduce the PM consumption. By employing a CP structure, the flux density amplitude can be enhanced. Moreover, due to uneven distribution of modulator poles on the armature teeth and fault tolerant teeth, the number of periods of modulator poles is only half of that of the stator teeth. Then, significant improvement in flux density working harmonics can be achieved. Furthermore, the superior electromagnetic decoupling capability can be achieved by introducing the fault-tolerant teeth. The relevant electromagnetic performance such as flux density, back electromotive forces, cogging torque and on-load torque have been calculated by using finite-element analyses, which have also been validated by experiments.