Numerical Thermal Analysis of Six-Phase PMSMs With Single- and Double-Layer Fractional-Slot Concentrated Windings in Healthy and Faulty Cases

Multiphase permanent-magnet synchronous machines (PMSMs) with fractional-slot concentrated windings (FSCWs) are favored for many uninterruptible applications due to their high fault tolerance and torque density. Two different configurations are often adopted: single layer (SL) and double layer (DL). For SL, each slot is filled with one phase winding, while for DL, two phases can share the same slot. Accordingly, many research papers advise adopting SL in fault-tolerant PMSMs, rather than DL, because SL offers higher physical, thermal, and electromagnetic isolation between phases. However, the lower thermal isolation, as for DL, may enhance the heat transfer. This could be expected to reduce the hot-spot temperature for DL. Thus, the established preference of SL over DL for fault-tolerant PMSMs may be questioned, and further analysis is necessary. This paper compares the temperature distribution of six-phase PMSMs between SL and DL FSCWs under both healthy and faulty conditions, considering open-circuit and short-circuit (interturn) winding faults. For accurate results, finite-element analysis and computational fluid dynamics are employed for the loss calculation and thermal simulation, respectively.