Optimal design considerations for interior permanent magnet motor for a range-extended electric vehicle

Interior permanent magnet motors (IPM) have been widely used in electric or hybrid electric vehicles due to their high efficiency and high power density. Frequent starts and stops, acceleration and deceleration of vehicles present heavy requirements for the drive motor. In this paper, a 4kW interior permanent magnet motor is designed for a small range-extended electric vehicle. A case study has been carried out for a range-extended solar-electric auto rickshaw, which is used extensively in Asian cities for point-to-point transportation with frequent starts and stops. Based on the specifications for the auto rickshaw, the optimal design processes of traction motor has been proposed, which includes specific considerations for determining dimensions of the stator and rotor, selection of slot-pole combination, skewing effect, the structure of rotor and permanent magnets, analysis of the pole-arc to pole-pitch ratio and reduction of active material in the motor. Analytical results obtained are verified by finite element analysis (FEA).