A method for predicting the electromagnetic noise of a permanent-magnet motor based on the coupling of electromagnetic force and modal is proposed. Firstly, a theoretical analysis and finite element method are combined to establish an electromagnetic force analysis model for a 6-pole 36-slot permanent-magnet motor used in vehicles. The spatial order and frequency characteristics of the electromagnetic force are analyzed. Then, the modal array of the motor is calculated using the finite element method, and the main sources of the motor vibration noise are predicted by combining the electromagnetic force with the modal frequency array of each order. Finally, a vibration noise multiphysics simulation analysis model is established using the finite element method, and the electromagnetic noise is calculated. The simulation results are consistent with the predicted results, verifying the effectiveness of the analysis method.

The built-in V-shaped permanent magnet motor can effectively utilize reluctance torque to improve torque density, but there is also a problem of large torque ripple causing high vibration noise. This article proposes a rotor structure with four magnetic isolation holes to reduce torque ripple in V-shaped built-in permanent magnet motors. Firstly, a finite element analysis model of the built-in V-shaped permanent magnet motor is established. The influence of slot width, rotor rib width, and magnetic bridge parameters on the torque of the permanent magnet motor was studied through parameterized scanning, and an optimization scheme was selected. Then, the position and size of the magnetic hole were optimized through an adaptive single-objective algorithm. Compared with the ordinary built-in V-shaped structure, the torque ripple of the built-in V-shaped permanent magnet motor with four magnetic isolation holes is reduced from 17.7% to 6.7%. The proposed internal V-shaped rotor structure with magnetic isolation holes and the optimization method can effectively reduce torque ripple, thus effectively solving the problem of vibration noise caused by torque ripple.