Investigation of a Double-Stator Dual-PM Hybrid Excitation Machine With DC Bias Current

This article investigates a double-stator dual permanent magnet (dual-PM) hybrid excitation machine (DS-DHEM) with dc bias current. Integrated winding accommodated on the outer stator can produce the armature field and excitation field simultaneously with the dc bias current to improve the efficiency and flux regulation capability, and the dual consequent-pole PMs on the inner stator and rotor are proposed to enhance the torque density. The working principle of the proposed DS-DHEM is based on multiple working harmonics introduced by three excitation sources and flux modulation effect, which is demonstrated by developing magnetic motive force (MMF) and permeance models. The influence of key parameters is studied, after which the multiobjective genetic algorithm (MOGA) is exploited to optimize the global design parameters. In addition, the stator-PM is found to have the largest torque contribution for DS-DHEM with the frozen permeability (FP) method. The comparative studies between DS-DHEM and an existing dual-PM hybrid excitation machine (DP-HEM) are performed to convincingly verify the superiority of DS-DHEM, which exhibits larger torque density, higher efficiency, and better flux regulation capability. Finally, a prototype is manufactured to conduct the experimental tests to validate the proposed machine.