Flux-Concentrated External-Rotor Switched Flux Memory Machines for Direct-Drive Applications

In this paper, an external-rotor switched flux hybrid magnet memory machine with a flux-concentration design is developed. Due to the external-rotor configuration, the stator design space is enlarged to alleviate the stator geometric conflictions existed in the internal rotor machine. Meanwhile, the spoke-type permanent magnet (PM) structure is designed to cope with the reduced armature slot area in its original “U”-shaped PM counterpart. In addition, the high-efficiency operation within a wide range of speeds and loads can be achieved. The topology, flux-adjusting principle and distinct features are introduced. Thereafter, the key design parameters including the stator/rotor pole combination, PM hybridizing ratio, and LCF PM thickness are optimized. Finally, the electromagnetic characteristics of the proposed machine are investigated and quantitatively compared with that of its“U”-shaped PM counterpart, which confirms the advantages of the proposed design.