Roles of coercivity and remanent flux density of permanent magnet in interior permanent magnet synchronous motor (IPMSM) performance for electric vehicle applications

摘要

We used four rotor topologies of an interior permanent magnet synchronous motor (IPMSM) to investigate the effects of remanent flux density ( B sub r /sub) and coercivity ( H sub c /sub) of permanent magnet on motor performance. Commercial strontium hexaferrite (SrFesub12/subOsub19/sub: energy product, ( BH )submax,/sub of 4.62 MGOe) and Nd-Fe-B (( BH )submax/sub of 38.2 MGOe) magnets were used for the rotor designs. The same machine specifications and magnet volume keep constant, while the H sub c /sub and B sub r /sub vary to calculate torque and energy efficiency with the finite-element analysis. A combination of high H sub c /sub and low B sub r /sub more effectively increased maximum torque of IPMSM when the hexaferrite magnet was used. For Nd-Fe-B magnet, the same combination did not affect maximum torque, but increased energy efficiency at high speed. Therefore, the H sub c /sub value of a permanent magnet is more effective than the B sub r /sub in producing high maximum torque for SrM-magnet based IPMSM and high energy efficiency at high speed for Nd-Fe-B magnet based IPMSM.