A Spoke-Type PM Machine with Quasi-Trapezoid Magnets and Quasi-Dovetail Iron Poles

This paper proposes a spoke-type PM machine with quasi-trapezoid magnets and quasi-dovetail iron poles (SPM-QMQI). The SPM-QMQI can offer several merits. First, the employment of quasi-trapezoid magnet and iron pole help to achieve strong flux-focusing effect and high saliency ratio, respectively, which contributes to enhancing torque output of the SPM-QMQI machine. Second, the quasi-dovetail iron can enhance flux-shielding effect and thus the rotor yoke can be replayed with low-density non-ferromagnetic material contributing to reducing rotor mass. Besides, the dovetail-shaped iron pole can protect the rotor magnet against centrifugal force, and thus the conventional rotor sleeve can be removed contributing to a small airgap length. Third, the magnet usage efficiency of electrical machine can be increased greatly, because of the magnet volume reduction and torque improvement. First, the schematic structure and characteristics of proposed QMQI pole pattern are presented. Subsequently, the impact of the key structural parameters and current angle of the QMQI pole pattern on the output characteristics of the electrical machine is investigated. Following that, the electromagnetic characteristics of the proposed QMQI pole design, such as airgap magnetic field, back electromotive force, torque output and ripple, magnet loss, rotor mass and magnet utilization ratio, are compared with with those of the conventional electric machine design to confirm the merits of the proposed SPM-QMQI design. The SPM-QMQI machine have high torque output, low rotor mass and small magnet volume simultaneously, which is desirable for many industrial applications.