전압 고조파를 고려한 전기 자동차 구동용 매입형 영구자석 동기 전동기의 특성 해석 및 설계

Abstract

The application of interior permanent magnet synchronous motors (IPMSMs) are getting widened from small home appliance to large traction motors due to high torque density , wide operating speed range, and high efficiency. These characteristics are suitable for electric vehicle (EV) traction motor requiring compact size and high efficiency. High torque density is achieved by utilizing both magnetic torque from permanent magnet and reluctance torque from difference of reluctance. Field weakening control enables wide operating speed range. The analysis and design of IPMSM are quiet challenging since their characteristics of hybrid torque production, high dependency to current vector, and non-linear motor parameters. In the high speed region, field weakening control is generally applied and large voltage harmonics are observed, which are not considered in conventional d-q axis equivalent circuit analysis. Consequently, required maximum speed can not be achieved with given input voltage. Voltage harmonics in the field weakening are modeled and equations for d-q axis equivalent circuit analysis are introduced based on classical impedance model. The analysis results considering voltage harmonics are verified by finite elements analysis and experiments. In addition, design considerations related to the high torque and wide operating speed range are summarized. Sizing rule, selection of pole/slot combinations, choice of core materials, analysis of eddy current loss and irreversible demagnetization of permanent magnet, centrifugal force analysis of rotor, etc. are concerned. Consideration of voltage harmonics give the solution to general problem in the high speed region with field weakening and design considerations give a guide line in designing IPMSMs for EVs.