Investigation of an Axial-Field Flux-Modulated Multiple-Permanent-Magnet-Excited Machine

In this paper, an axial-field flux-modulated (AFFM) machine with multiple permanent-magnet (PM) excitations for electric vehicle applications is investigated. This study addresses the torque limitation of axial-field rotor-PM machines by investigating the strategic placement of stator PMs with specific magnetization directions, rather than solely relying on increased rotor PM quantity which becomes ineffective beyond certain thresholds. Then, taking axial-field magnetic gears with a gear ratio of 19/5 as the foundation, the evolution processes into corresponding stator-PM and rotor-PM axial-field motors are explored. The physical structures and necessary magnetic coupling conditions of these two topologies are discussed in detail to enhance the performance of the proposed topology. Then machine characteristics, including the flux linkage, back-EMF, torque capability, self-and mutual-inductance, power factor and cogging torque are researched, wherein the torque output of the proposed one is comparable to the sum of stator-PM and rotorPM motors. The effects of specific parameters influenced by the assembly process are also investigated. To demonstrate the competitiveness, the proposed machine was compared against four regular AFFMPM topologies, achieving advancements in torque and PM utilization aspects. Finally, a prototype is manufactured and tested, verifying the FE predictions.