Impact of Rotor Pole Number on the Characteristics of Outer-rotor Hybrid Excitation Flux Switching Motor for In-wheel Drive EV

Abstract

This paper present the impact of rotor pole number on the characteristics of outer-rotor hybrid excitation flux switching motor (ORHEFSM) for in-wheel drive electric vehicle (EV) applications. In recent years, researches on in-wheel motor for EV drivetrain system become more popular due to their several advantages of independent wheel controllability and higher efficiency. In addition, it provides more cabin space caused by elimination of mechanical transmission gears as conventionally use in the most of existing EV with single motor propulsion system configuration. Moreover, the proposed motor has single piece of rotor making the motor more robust and suitable for high speed applications. Under some design restrictions and specifications, design principles and initial performances of the proposed motor at various rotor pole numbers with 12 stator slots are demonstrated. Initially, the coil arrangement tests are examined to confirm the operating principle and polarity of each armature coil phase of the proposed motor. Furthermore, the profile of flux linkage, induced voltage, cogging torque and torque characteristics at various field excitation current density conditions are analyzed based on 2D- finite element analysis (FEA). The results obtained show that the appropriate combination of stator slot-rotor pole configurations are 12S-10P which initially provide highest torque and power density. Thus, by further design refinement and optimization it is expected that the motor will successfully achieved the target performances.