Improvement of Reluctance Torque in Fault-Tolerant Permanent-Magnet Machines With Fractional-Slot Concentrated-Windings

Fault-tolerant permanent-magnet (FTPM) machines adopt fractional-slot concentrated-windings, thus reducing copper loss and improving fault tolerance. However, they usually suffer from insignificant reluctance torque. The novelty of this paper is to adopt some techniques to improve reluctance torque in FTPM machines, including rotor divisions between poles, two-layer interior magnets in oriented direction, and the specially designed flux barriers between two-layer magnets. The configuration of the newly designed FTPM machine is presented, and its inductance, electromagnetic torque, rotor losses, the flux-weakening capacity, and the speed range are analyzed by using the finite-element method. By using the new design, FTPM machines can offer high reluctance torque, low rotor losses, and good flux-weakening performance.