Design and analysis of a novel spoke-type motor to reduce the use of rare-earth magnet materials

In this study, a novel design for a tilted spoke-type hybrid permanent magnet synchronous motor (TH-PMSM) that uses two types of permanent magnet (PM) materials is proposed to reduce the consumption of rare-earth PM materials. The key feature of this motor is securing space by tilting the permanent magnet, so that more PMs can be used in the limited rotor space. In addition, based on the centre axis of the rotor, the rare-earth magnets are positioned deeper inside than ferrite PMs to maximise the torque density and reduce the leakage magnetic flux that occurs around the centre of the rotor. Moreover, unlike ordinary spoke-type rotors, it is designed with an integral core like the rotor of the interior permanent magnet synchronous motor (IPMSM), so it is structurally safe even at high speeds. To ensure that the proposed motor is efficiently designed, the output torque, PM cost, cogging torque, and torque ripple were compared with those of the conventional rare-earth PM motors with the same overall dimensions. The validity of the proposed motor was verified by the results of a finite element method simulation and experiments on the fabricated motor.