Finite element calculation of the saturation DQ-axes inductance for a direct drive PM synchronous motor considering cross-magnetization

Direct-drive torque-servo permanent magnet synchronous motor often operates in overload conditions. Its characteristic is evidently influenced by magnetic circuit saturation. The direct-axis and quadrature-axis inductances of surface mounted permanent magnet synchronous motor are usually considered as constant i.e. L_d=L_q. In fact, both the d-axis and q-axis inductances vary with load condition because of magnetic circuit saturation. A novel procedure is developed to calculate the dq-axes inductance with saturation by finite element method considering cross magnetization. Through magnetic field computation, the influence of saturation and cross-magnetization on dq-axes inductance is further investigated.