A Novel Counter-Rotating Axial-Flux Hybrid-Excitation Permanent Magnet Machine With Dual-Rotor

In order to better adapt to the load unbalance in the operation of a counter-rotating propeller (CRP), a novel counter-rotating axial-flux hybrid-excitation permanent magnet machine (CR-AFHEPMM) is proposed in this article, which combines the high torque density of the axial-flux permanent magnet machine (AFPMM) and the flexible flux adjustment of the hybrid excitation machine. The dc field windings are installed near the inner diameter of the soft magnetic composite (SMC) stator core with a special structure, enabling reverse adjustment of the air-gap magnetic field on both sides. Unbalanced load operation of two rotors can be realized without increasing the machine volume. First, the structural features and operation principle of the CR-AFHEPMM are presented. Then, the influence of slot-pole combination, permanent magnet (PM) arrangement and key structural parameters on the stable operation, output torque, and load unbalance range are studied. Finally, an optimal structure of the Halbach array consequent-pole PM rotor is further proposed and analyzed. The results show that the proposed CR-AFHEPMM is a promising candidate for the application of CRP.