헤어핀 권선을 이용한 EV 구동용 WFSM의 출력 밀도 개선 설계

Abstract

The rare earth material are dependent on imports from China for unstable supply and demand. Therefore the wound field synchronous motor (WFSM) which doesn’t use rare earth material is being studied. The most commonly used wire shape is circular, with fill factor of 40%. If the fill factor can be increased, the slot area can be decreased. The hair-pin winding used wire shape is square and fill factor of 60%. So, if the slot area is designed for using hair-pin winding, it can be designed smaller than slot area of initial model. By reducing the slot area, it is possible to increase the stator inner diameter and the rotor outer diameter. Then it is possible to reduce the stack length while maintaining the same torque. In conclusion, it is possible to reduce the motor weight and volume. Moreover, by designing a square shaped slot, it is possible to increase the width of teeth. This also reduces the saturation level, which in turn reduces the total harmonic distortion (THD) of the back electromotive force (BEMF). Therefore, by using a hairpin winding in motor design, the same output can be maintained while the volume and weight is decreased. The power density is increased. In this paper, by using a hairpin winding, stack length is reduced by 10% compared to the initial model while maintaining the same output. The initial and improved model is compared by calculating the power density and efficiency of the motor by using a Two-Dimensional Finite Element Method (2-D FEM).