Analytical Calculation and Analysis of Electromagnetic Vibration-Excitation Sources for Near-Pole Slot Permanent Magnet Motors

In response to the problem that the contribution of the tangential electromagnetic force wave to the electromagnetic vibration and noise of permanent magnet motors with near-pole slots cannot be ignored, an analytical model of surface-mounted permanent magnet motors is established using the Fourier series method. By means of the vector magnetic potential and boundary conditions, the analytical expressions of each subdomain are solved, thereby establishing the relationship between the tangential electromagnetic force wave and the main structural parameters of the motor. Based on this, the influence laws of the slot opening width, air gap width, and permanent magnet thickness on the 2nd order radial electromagnetic force wave and the 2nd order tangential electromagnetic force wave of the motor are studied. The correctness of the analytical method is verified by comparing the finite-element results with the analytical ones. Additionally, a permanent magnet shaping structure is proposed to reduce the 2nd order electromagnetic force wave of the motor and optimize the output performance of the motor. This analytical method can reflect the relationship between the radial and tangential electromagnetic force waves and the main structure of the motor, and can be applied to the initial design and optimization of permanent magnet motors with semi-open slots for achieving low vibration and noise.