Fault-tolerant IPM machine with mixed-layer fractional-slot concentrated-winding

To increase the fault tolerance of interior permanent magnet (IPM) machine, an optimized 9-slot/8-pole IPM machine with mixed-layer fractional-slot concentrated-winding is presented and analyzed. A comparison of the electromagnetic performance and fault tolerant capability between the proposed machines and their conventional double layer counterpart is carried out. It is found that 9-slot/8-pole machines with a mixed-layer winding can achieve a higher winding factor, more than 30% higher self-inductance and a near-zero mutual inductance that is only 2.2% of that of its double layer counterpart. This helped the mixed layer 9-slot/8-pole IPM machine achieve better fault tolerant capability and smaller three phase short-circuit current, while having higher average torque (albeit with higher torque ripple) and comparable copper loss.