Analytical calculation of air gap magnetic field distribution in vernier motor

This Paper aims to analyze the characteristics of a surface permanent magnet vernier motor (SPMVM) according to its design parameters such as a magnet thickness on its rotor and stator slot opening ratio based on its operational principle. The vernier motor is a kind of electric motors with a magnetic gear effect and has high torque characteristics at low speeds without mechanical gears. The vernier motor also has various advantages such as low noises and maintenance-free operations. The SPMVM is operated using space harmonics of the magnetic flux density distribution in the air gap which is created by the magnetomotive force (MMF) due to the permanent magnet and air gap permeance. This paper presents an analytical calculation method of the vernier motors, and their results are compared with those of 2-D finite elements method (FEM). Firstly, the operational principle of the SPMVM and the magnetic flux density in the air gap are described in detail. Secondly, the harmonics of the magnetic flux density in the air gap are analyzed according to the design parameters. Finally, the best design parameters are determined, and the 2-D FEM results verify the analytical calculation method.