Analysis of Torque Characteristics of Built-in Uneven Air Gap Permanent Magnet Synchronous Direct Drive Motor for Heavy Duty Locomotive

In order to meet the demand of high torque density and stable operation of permanent magnet synchronous direct drive motor (PMSDDM) for heavy load locomotive, the rotor structure with uneven air gap was used to improve the amplitude of air gap magnetic field fundamental wave, so as to improve the electromagnetic torque and reduce the cogging torque of PMSDDM. The uneven air gap ratio k, the ratio of maximum air gap to minimum air gap, was scanned by finite element simulation software. By comparing the fundamental wave amplitude of air gap magnetic field, cogging torque and electromagnetic torque under different values of k, the trend of their changing with k were obtained, so the optimal value of k was determined. The simulation results showed that the reasonable uneven air gap can improve the electromagnetic torque of PMSDDM, at the same time reduce the amplitude of the cogging torque. The performance of PMSDDM was improved.