Design study of single phase outer-rotor hybrid excitation flux switching motor for hybrid electric vehicles

In electric machine, there are several types that are practical for EVs. However, most of commercial EV including these types of motors used single motor and transmission gears coupled to the wheels. This system leads to the transmission losses and reduce the efficiency and reliability of the motor. Therefore, in-wheel direct drive mechanism is introduced to overcome this problem. In-wheel direct drive eliminates the mechanical transmission, differential gears and drive belts. Thus, in-wheel direct drive provides quick torque response, higher efficiency, weight reduction, and increased vehicle space. As one of alternative, a new design of hybrid excitation flux switching motor (ORHEFSM) for in-wheel drive EV is proposed. In this paper, the design optimization of single-phase 8S-4P outer-rotor HEFSM is presented. Initially, design procedures of the HEFSM including parts drawing, materials and conditions setting, and properties setting are explained. Then, coil arrangement tests are examined to confirm the machine operating principle and position of each armature coil phase. Finally, flux comparison of PM, DC FEC and PM with DC FEC, flux linkage at various FEC current densities, J_E, flux distribution and flux line of PM with FEC, cogging torque, Induced voltage/ back EMF of PM, DC FEC and PM with DC FEC, Combination of FEC and Armature Coil Flux Characteristic (FEC + Armature Coil), and torque and power versus FEC current density, J_E at various armature coil current densities, J_A are also analyzed. As a result, the performance of the improved design motor shows that the maximum torque achieved is 96.8% of the target performance, whereas the maximum power has achieved 56.3 kW which is greater than the target value. Thus, by further design refinement and optimization it is expected that the motor will successfully achieve the target performances.