Investigation of the electromagnetic characteristics and operating performance of a bidirectional PM excited machine

This paper presents a study of bidirectional permanent magnet excited machine (BPMEM) based on the study of field-modulation permanent magnetic gear machine (FPGM). The BPMEM structure includes the installation of consequent-pole permanent magnets (PMs) on both the stator and rotor sides of the FPGM so that the stator and rotor can be bidirectionally excited to increase the working airgap flux density amplitude, reduce the flux leakage between poles, and increase the torque density. Therefore, the paper first analysis the influence of different airgap structures and PM arrangements on the airgap flux density and studies the winding slot–pole combination and the resulting working flux density harmonics to analyse the electromagnetic torque generation mechanism. By using the finite element analysis (FEA), the quantitative analysis and comparison of the FPGM, slot-wedge-less FPGM (SWL-FPGM), consequent-pole FPGM (CP-FPGM) and BPMEM verify the superiority of BPMEM in improving electromagnetic torque. In addition, the paper also studies the key performance of BPMEM’s overload capacity, power factor and flux-weakening capability. Finally, no-load and independent load experiments are carried out on the FPGM prototype to verify the correctness of the FEA model and analysis method of the machine in this paper.