Analysis of an innovative less-rare-earth reverse salient-pole axial flux permanent magnet synchronous motor with variant rotor topologies

Purpose Axial flux permanent magnet (AFPM) motors face challenges in achieving high-speed operation and suffer from the high cost of permanent magnet materials. To improve the speed expansion capability of the motor and reduce motor costs, a new type of less-rare-earth reverse salient-pole axial flux motor was proposed by adopting a combination of magnetic poles and adding magnetic barriers. This design achieved the reverse salient-pole characteristics of an axial motor and improved the constant power speed regulation range of the motor. Design/methodology/approach This paper designs a double-stator axial flux motor featuring alternating ferrite-neodymium-iron-boron poles and alternating iron-core poles with reverse-salient poles. First, the evolution of the motor topology is introduced. Second, the equivalent magnetic circuit of the designed motor is analyzed. By opening magnetic barriers in the rotor and using an alternating ferrite-neodymium-iron-boron pole method, the reverse salient-pole characteristics of the axial motor are achieved and the manufacturing cost of the motor is reduced. Finally, the structure of the magnetic barriers used to achieve the reverse salient-pole in the axial motor is optimized, and the electromagnetic performance of the three optimized motors is compared. Findings The results show that the ferrite-NdFeB alternating structure CP-AFPM-A has better overall performance, the cost of its permanent magnet material is reduced by 40% compared with that of CAFPM and CP-AFPM-A possesses a higher speed regulation capability and a wider range of constant power regulation when the rotational speed is up to 3,500 r/min. Originality/value Compared with traditional surface-mounted axial flux motors, the rare-earth-reduced reverse salient-pole axial flux motor proposed in this paper not only reduces motor costs but also, due to the characteristics of its reverse salient-pole, holds significant engineering value in expanding the motor’s speed regulation range during high-speed operation.