On the feasibility of integer and fractional number of slots per pole distributed winding designs for synchronous reluctance motors

This paper presents a feasibility study between a design for synchronous reluctance (SyncRel) motors with integer slots/pole, i.e. 36 slots/4poles and fractional slots/pole, slots per pole ratio higher than 3, i.e. 18 slots/4poles configuration. The analysis is extended also to low energy permanent magnet assisted synchronous reluctance motor (PM SyncRel). It is found that the integer slots/pole solution have a better efficiency for SyncRel, while fractional slots/pole solutions benefit the PM SyncRel design. Potentially, integer slots/pole designs might have higher torque ripple and lower power factor than fractional slots/pole solutions. The presence of very low energy permanent magnets, as bonded plastic ferrite leads to significant increase in the constant torque speed range and power output.