A PM Pole With Axial Varied Width for Vibration Mitigation in PM Brush DC Motors

This paper presents a PM pole with varied width in the axial direction for vibration mitigation in permanent magnet brush dc motors, which is proposed to decrease the deformation caused by radial pulsating force and bending moment together. First, the air gap flux density distribution and radial force density distribution are derived in detail. After two types of vibration modes and their reasons as pulsating force and bending moment are analyzed, the difficulty in vibration mitigation is pointed out. By investigating the change rule of the pulsating force and bending moment with PM pole width, a type of PM pole with varied width in the axial direction is proposed. Its principle of deformation reduction is presented, and the optimized pole shape is derived. A three-dimensional finite-element method is used to calculate the magnetic field, Maxwell force, modal analysis, and deformation of motors. In order to verify the effectiveness of the proposed method, the vibration of the proposed motor is compared with the other three types of traditional motors, including skewing slot or skewing pole. Finally, experimental results of two types of motors are compared to validate the proposed technique.