A Concentrated-Flux-Type PM Machine With Irregular Magnets and Iron Poles

Most industrial applications concern output torque, rotor mass, and utilization of rare Earth permanent-magnet (PM) material of electrical machines. Generally, it is challenging to improve these aspects simultaneously. The objective of this article is to propose a novel concentrated-flux-type PM machine with irregular magnets and iron poles (CPMIP). The configuration has following advantages. First, the employment of quasitrapezoid magnets with opposite magnetization direction and large cross-section helps to enhance the flux-focusing effect and thus the torque generation. Second, the quasitriangular iron poles can improve the magnetic self-shielding effect well, and thus the rotor yoke can be removed completely and the rotor mass could be reduced significantly. Third, due to the reduction of PM volume and the improvement of torque output, the PM utilization ratio of electrical machine can be increased greatly. The schematic structure and pole patterns of the proposed electric machine are presented. Subsequently, the equivalent magnet circuit is established to validate the performance improvement of the CPMIP machine. Then, the design improvement with offset iron-pole arc is proposed to suppress torque ripple and balance torque output and PM utilization ratio capability well. Following that, an electrical machine with the irregular magnets and iron poles is designed. Then, the electromagnetic characteristics of the proposed pole designs are compared with those of the electric machines with conventional radial, Halbach, and consequent-pole patterns. Finally, the research prototype is developed, and experiments are conducted to verify the design concept and analysis of CPMIP machine.