A novel multi-pole permanent magnet synchronous machine with SMC bypass core for magnet flux and SMC field-pole core with toroidal coil for independent field strengthening/weakening

This paper presents a novel multi-pole permanent magnet synchronous machine for the traction applications in which both high torque capability at low speed and wide speed operating range are required. The origin of the proposed machine construction is from a hybrid stepper machine, but the uniqueness lies in the utilization of soft magnetic composites (SMC) as magnet flux bypass core and filed-pole core with toroidal coil. Because of the magnetically three-dimensional isotropic nature of SMC, the SMC-bypass core for magnet flux makes it possible to avoid unnecessary magnet mmf loss due to a passage through inter-lamination airgap. For the same reason, the SMC-field pole can deliver three-dimensional flux and the mmf of the fitted field toroidal coil can theoretically contribute to providing independent field strengthening/weakening capability. First, the rough design of the proposed machine based on an equivalent magnetic circuit analysis is described. Second, the performance prediction and the design refinement using 3D-FEM are demonstrated