Rated optimal current control angle identification for surface permanent magnet vernier motor considering magnetic saturation

Abstract

Due to the non-salient structure, <italic>i_d</italic> = 0 control is used at the rated operating point to achieve the maximum torque for surface permanent magnet vernier motor (SPMVM). However, the assumption is based on no magnetic saturation in the iron core. Achieving high power factor using this control method significantly sacrifices the torque density and constant power speed range (CPSR), either by reducing the electric loading or declining the winding inductance. This paper proposes an analytical approach to identify the optimal current control angle at the rated point for SPMVMs considering the magnetic saturation to achieve high power factor while maintaining high performance of the other two metrics. The proposed analytical method includes the evaluation of the flux density and magnetic reluctance in the stator core by analyzing the flux interaction between permanent magnet (PM) and armature winding. The obtained magnetic reluctance is used to identify the optimal current control angles for geometries with different motor parameters. The result shows that when the optimal current control angle is utilized, a specific design can be found to achieve higher torque density, higher power factor and wider CPSR than the globally optimized candidate using <italic>i_d</italic> = 0 control at the rated point. Finally, a prototype is manufactured to confirm the validity of the proposed modeling technique and the performance improvement assumption by considering the current control angle.