Design for Improving Drive Performances of Variable Flux SPMSM for Eco-Car Race Employing Mechanical Stator Mover System

This paper presents a design study on improving the operating range and lowering the cogging torque for a variable flux surface-mounted permanent magnet motor (VFSPMSM) with a variable airgap structure employing a mechanical stator mover system for the eco-car race called Ene-1 Challenge. Eco-car race application requires designing a traction motor with a wider operating range and higher efficiency under given battery voltage and current regulations. To realize these requirements, the VFSPMSM can change the back-emf constant based on the motor speed by adjusting only the axial alignment between stator and rotor appropriately based on the mechanical stator mover system, resulting in a wider operating speed range without field weakening control. Additionally, it is essential to achieve the lowest cogging torque possible to ensure driving comfort. The design procedure of a VFSPMSM for operating range expansion is examined based on the problems found in the previously designed motor. Finite element method-based design and simulation and experimental drive performance evaluation results of the designed VFSPMSM without field wakening show an extended operating range, improved motor efficiency and minimized cogging torque.