Eddy current loss mitigation in permanent magnet synchronous machines with modular structure

Abstract

This paper discusses the design and performance analysis of a permanent magnet synchronous machine (PMSM) for low-speed, high-torque shaft generators. A 216-slot and 60pole (216 S 60 P) combination was selected, based on a 36S10P design with a coil span of three, which allows for a modular structure of both windings and cores. A comprehensive 2-D finite element analysis was conducted under rated conditions to evaluate the effects of segmented stator and rotor structures on average torque, torque ripple, core losses, and eddy current loss of the permanent magnet. The study revealed that an optimized segmentation of the rotor yoke with a non-magnetic rotor rim led to a substantial reduction in subharmonic fluxes, resulting in a significant decrease in the eddy current loss by as much as 80%. The findings open new possibilities for the design and application of modular PMSMs, promising improved efficiency and maintenance convenience in large-scale marine applications.