인덕턴스 고조파의 위상을 고려한 동기전동기의 평균토크 감소 없는 토크리플 저감

Abstract

Recent development trends for automobile are high speed, high power and high efficiency. Therefore permanent magnet motors are used in various automobile parts because of high torque density and wide operating range. Especially, interior permanent magnet synchronous motors are applied in many automobile application where structure is robust and manufacturing is easy. In these motors, torque ripple reduction is critical issue because the torque ripple does not contribute to power and has harmful effect on noise and vibration. Consequently, many researchers have studied the issue and most of the researches are on reduction methods. A new winding method or shape modification is used for the torque ripple reduction however average torque decreases. In the thesis, torque components are separated, harmonic analysis of torque ripple is conducted and the method of reducing torque ripple without decrease in the average torque is suggested by considering phase of harmonic components. Torque is calculated by induced voltage, current and speed of revolution where the components are current variation, inductance variation and rotation of permanent magnet. In the thesis, interior permanent magnet synchronous motor for oil pump of 800W is selected for the reference model and a sinusoidal current is considered for the analysis of torque components. Torque ripple can be reduced by modifying the shape of motor to increase the effective air gap length such as eccentricity and chamfer where the magnitude of inductance is reduced which is the component of the torque. However, the average torque is also reduced by applying the above method. Therefore, in the thesis, the method of reducing torque ripple considering the phase differences in torque components is suggested where magnitudes of the components are similar to maintain the average torque. The phase differences are obtained by an asymmetric structure such as asymmetric magnetic rib and asymmetric permanent magnet shape. In the thesis, the asymmetric permanent magnet shape is used with the same magnetic rib and pole arc. Response surface methodology is used to decide the optimum position and rotation angle of permanent magnet. Finite element analysis is conducted to verify the suggested method and torque ripple reduction without decrease in the average torque is checked. Furthermore, eccentricity model performing the similar torque ripple is compared and torque ripple reduction with decrease in the average torque is checked. Electrical and mechanical characteristics of three models which are reference model, asymmetric model and eccentricity model are compared. These models are manufactured and tested to verify the suggested method. This thesis suggests the method of torque ripple reduction without decrease in the average torque considering phases of torque components and the method can be useful to obtain the performance of permanent magnet synchronous motor.