Design of a Novel Spoke-type IPM Motor with Surface-mounted Magnets to Improve Torque Characteristics

Abstract

This paper proposes a novel strategy of spoken-type IPM motor with four surface-mounted magnets to improve torque density and decrease torque ripple, in which the motor is with ferrite magnet. The asymmetrical rotor structure concept is used during the design process to make the two torque compositions of the spoken-type motor - the reluctance torque and the magnetic torque – get a better utilized. Under this design, the torque is improved by making the maximum values points of the magnetic torque and the reluctance torque be close to each other. To verify the analysis result, the frozen permeability method (FPM) is employed to provide feasible insights into the separation of the torque components based on a 2-D finite element method (FEM). To highlight the superiority of the proposed model, a conventional spoken-type IPM motor with symmetrical rotor structure is adopted for comparison under the same magnet amounts, machine size and operating conditions.