An analytical model of unbalanced magnetic pull for PMSM used in electric vehicle: Numerical and experimental validation

Permanent magnet synchronous motors (PMSM) are now the focus of application in electric vehicle. Unbalanced magnetic pull (UMP) have been identified as the main cause of noise and vibration in PMSM, rather than torque ripple and cogging torque. In this paper, analytical model of unbalanced magnetic pull from non-uniform magnetic field is investigated theoretically based on Maxwell stress tensor approach. Then, a procedure for calculating magnetic forces based on the 2-D finite element method (FEM) is presented. The FEM results validate the magnet distribution and UMP of analytical results. Also, experimental measurement of electrical quantities and forces with static eccentricity were carried out with one special test fixtures. The analytical model is validated by comparing their results with finite-element and experimental under statistic and dynamic eccentric. Relying on the unique assumption of one-dimensionality, the present analytical model appears as a useful tool for parameters design and behavior understanding.