Design considerations and performance improvement of a dual-stator PM vernier motor with axial-flux loop

This paper presents a study on design parameters of a permanent magnet vernier motor (PMVM), to discuss their influences independently for motor performance improvement, where the electromagnetic torque and torque ripple are mainly taken into consideration. Basic model of the PMVM is designed with dual-stator, axial-flux topology, spoke-type magnets array, which has the feature of high torque density and relative high power factor at low speed for the direct-drive systems. Compared to a radial-flux motor, the axial-flux motor has non-equal radii in inner side and outer side, which results in extra design considerations in terms of stator slot shape, rotor core shape, and asymmetric overhang lengths. Therefore, the design parameters of slot shape, winding method, rotor core, and rotor overhang length are discussed based on the basic model of axial-flux PMVM under the constraint of motor volume. Motor characteristics are illustrated and analyzed using three dimensional finite element method (3D FEM). Finally, one prototype of optimal designed model is manufactured and tested to verify the improved motor characteristics.