High-Performance Partitioned-Stator Switched Flux Memory Machines with Hybrid Magnets on External Stator for Traction Applications

This paper proposes and investigates a new topology of switched flux memory machine, in which the hybrid magnets and armature windings are separately located on external and inner stators, respectively. Due to the effective online permanent magnet (PM) magnetization, the excitation copper loss can be eliminated. Hence, the high efficiency can be maintained across a wide range of speeds and loads, which is desirable for traction applications. Meanwhile, the partitioned stator (PS) design is beneficial to the alleviation of geometric conflicts between magnetic and electric loadings. In addition, the fact that armature windings are located in the inner stator leads to the increase of effective split ratio similar to an external-rotor machine design. Consequently, the torque capability can be further improved compared to its inner-PM counterpart. The machine topologies having PMs mounted on either external or internal stator are introduced first. The design considerations for the slot/pole combination are investigated. Based on the identical basic specifications, the major electromagnetic characteristics of the optimally designed external-PM machine are investigated in comparison to those of its internal-PM counterpart. The analysis results reveal that the EPM-PS-SFMM can provide wider flux regulation range, higher torque capability as well as lower torque ripple than its IPM counterpart, which confirms the validity for the proposed design.