Analytical Torque Ripple Prediction Using Air-Gap Permeance and MMF Functions in PM Synchronous Motors

Apart from the stator slot permeance, interior permanent magnet synchronous motor (IPMSM) has a rotor permeance which varies depending on the rotor angle. The two permeances appear as two parallel conductance elements in the magnet circuit modeling. In adding them, Taylor series approximation is utilized. Together with stator and rotor magneto-motive forces (MMFs), air-gap field is calculated analytically. Further the analytical modeling is extended to the torque calculation based on Maxwell stress tensor. The analytical results are compared with finite element analysis (FEA).