매입형 영구자석 동기기의 PWM 전류 고조파를 고려한 철손 및 시스템 효율 분석

Abstract

Large-capacity batteries are applied to vehicles to improve the mileage of electric vehicles. However, increasing the capacity of the battery degrades the heating and cooling characteristics of the motor-inverter system. The increase in heat generation of the motor-inverter system causes a decrease in efficiency and a decrease in acceleration and deceleration performance of the vehicle driving system. Therefore, design and control for a high-efficiency motor-inverter system is required, and for this purpose, it is necessary to accurately predict the efficiency of each component. In this paper, we analyze the loss of a motor in consideration of the harmonic current (Pulse Width Modulation current harmonic) caused by inverter switching action, and propose a method to predict the efficiency of the motor-inverter system. For the loss of the motor, DC and AC copper losses and iron losses were considered, and mechanical losses were ignored. The loss of the inverter takes into account the conduction loss and the switching loss. And by comparing this with the motor loss at the sinusoidal current, it was confirmed that the proposed method was similar to the actual trend. Additionally, we calculated PWM current harmonics according to switching frequency and analyzed trends in motor efficiency and system efficiency. Through this, the necessity and validity of predicting motor loss and system efficiency in consideration of PWM current harmonics were verified.