Analysis of Electromagnetic Torque and Effective Winding Inductance in a Surface-Mounted PMSM During Integrated Battery Charging Operation

During integrated charging (IC) from a single phase ac utility employing permanent magnet machines, the magnetic field produced by the sinusoidal ac current passing through the stator windings: 1) affects the effective winding inductance used in the charger circuit as a function of different stator winding combinations and 2) produces oscillating torque of varying magnitudes as a function of rotor position. Understanding these challenges, this paper exclusively investigates the electromagnetic effects inside a surface-mounted permanent magnet synchronous machine (SPMSM) when it is used for IC operation in electric vehicles. Variation of oscillating electromagnetic torque magnitude as a function of rotor angle is investigated through finite-element analysis, and recommendations are provided to determine the lowest torque position favorable for IC operation. Thereafter, numerical investigations are conducted for five different stator winding combinations to analyze the issue of varying effective inductance as a result of magnetic coupling in the motor. Furthermore, a mathematical model is developed to obtain these inductances in the five winding configurations. Finally, the numerical investigations are validated by performing experimentations on a 21 hp SPMSM.