Design and analysis of high-power/high-torque density dual excitation switched-flux machine for traction drive in HEVs

This paper presents design viability studies and investigations of dual excitation switched-flux (DESF) motor as an applicant for traction drives in hybrid electric vehicles (HEVs). First of all, the main structure, the fundamental principle of operation and the design notion of the recommended DESF motor are discussed. Then, under certain limitations, specifications and performances of conventional interior permanent magnet synchronous (IPMS) motor, the preliminary performances of the recommended DESF motor are evaluated based on two-dimensional Finite Element Analysis (FEA). Since the initial performances fail to attain the target torque and power, design optimization based on deterministic approach of several DEFS motor parameters is applied in an attempt to attain the target performances. After a few cycles of design optimization, the improved DEFS motor has achieved the target power and torque of 123 kW and 333 Nm, respectively. In addition, due to definite advantage of robust rotor structure of DESF motor, rotor mechanical stress prediction at highest speed of 12,400 r/min is much lower than the mechanical stress in conventional IPMS motor. In conclusion, the final design DESF motor has the maximum torque of 11.97 Nm/kg and power density of 5.83 kW/kg, which is approximately 26% and 66% more than the torque and power density in existing IPMS motor.