Permanent magnet coupling air gap magnetic field reconstruction and torque performance analysis

This paper investigates the nonlinear distribution characteristics of the internal air-gap magnetic field of a permanent magnetic coupling with 18 pole pairs. A novel analytical calculation method based on the equivalent surface current method is proposed to accurately reconstruct the air-gap magnetic field. Discretization and programming using MATLAB were employed to solve for the magnetic field distribution and periodicity. Additionally, based on the Maxwell stress tensor method, the electromagnetic torque of the permanent magnetic coupling was calculated, establishing a relationship between the air-gap magnetic field distribution and torque performance. COMSOL finite element simulation software was used to analyze the coupling's air-gap magnetic field. The results demonstrate that the air-gap magnetic field exhibits periodic distribution, with the period determined by the number of pole pairs. Moreover, the torque performance is directly affected by the air-gap magnetic field, showing a similar periodic distribution. The analytical results are in good agreement with the simulation results. This study provides theoretical support for optimizing the design of permanent magnetic couplings and offers a new solution for the efficient and accurate calculation of the air-gap magnetic field and the analysis of transmission performance.