Design and analysis of a two-phase brushless DC motor with hybrid permanent magnet material for only-pull drive technique

Abstract

This paper proposes a two-phase radial flux brushless DC motor comprising a rotor decorated with hybrid permanent magnet (PM) material, i.e., rare-earth NdFeB magnets combined with ferrite magnets. The rare-earth NdFeB magnets are used on the surface, and ferrite magnets in the spoke-type configuration. The combined surface and spoke-type topology are used to improve the output torque as well as to protect magnets of different grades against irreversible demagnetization. The motor is operated using the only-pull drive technique, which allows the use of thin magnets in the motor without the effect of irreversible demagnetization. The electromagnetic performance of the proposed motor is compared with those of a two-phase surface-type PM motor and the spoke-type motor, all driven by the only-pull drive technique. Furthermore, the operating point of the ferrite magnets is analyzed using finite element analysis to confirm the demagnetization endurance of the proposed motor.