Mechanism and Suppression of Torque Ripple of Dual-Parallel Rotor Permanent Magnet Synchronous Motor

In extruder, two-roll mill, twin-screw pump and other parallel driving mechanical equipment, the current driving mode is an induction motor to drive the drive shaft, and the drive shaft transmits the torque to the driven shaft through the synchronous mechanical gear. This transmission mode has some problems, such as large system volume, low system efficiency, difficult sealing, and regular maintenance. Therefore, the dual-parallel rotor permanent magnet synchronous motor has gradually attracted attention. Due to the absence of partial stator core and windings, the dual-parallel rotor permanent magnet synchronous motor has a large torque ripple, which limits its application in parallel drive machinery. In this paper, the mechanism of torque ripple in dual-parallel rotor permanent magnet motor is analyzed, and the corresponding suppression methods are proposed. Firstly, the advantage of N-S type rotor is illustrated by comparing the N-N type and N-S type two rotor structures. On this basis, the mechanism of torque ripple is studied. According to the different influencing factors, the mechanism of cogging effect, end effect, permanent magnet gear effect and winding parameter asymmetry on the motor torque ripple are analyzed step by step, and the analytical expression of each torque component is constructed. Secondly, the correctness of theoretical analysis is verified by finite element model. According to the different components of torque ripple, the corresponding suppression methods are proposed. The suppression of no-load torque can be realized by optimizing the structure parameters of the motor, and the suppression of ripple torque can further be realized by optimizing the windings position distribution. Finally, a prototype test platform is built to verify the accuracy of the analytical model. The following conclusions can be drawn from the simulation analysis: (1) The torque ripple of dual-parallel rotor permanent magnet synchronous motor comes from four components, namely, cogging torque, end effect torque, permanent magnet gear transmission torque and ripple torque caused by asymmetry of winding parameters, and the first three components are collectively referred to as no-load torque. (2) No-load torque is the main component of torque ripple, ripple torque is a secondary component of torque ripple. The 2nd harmonics, 12th harmonics and 24th harmonics in no-load torque are the most important components. Among them, the 2nd harmonic is caused by the end effect torque and the permanent magnet gear transmission torque, the 12th harmonic and the 24th harmonic are caused by the cogging torque. The 12 harmonics content in ripple torque is the largest. (3) The no-load torque of the motor can be effectively suppressed by optimizing the structural parameters of the motor, such as the polar arc coefficient of the permanent magnet, the eccentricity of the permanent magnet, the duty angle, the coupling distance, and the shape of the core end at the splice. Ripple torque can be suppressed to some extent by optimizing the winding position distribution. © 2024 China Machine Press. All rights reserved.