Modelling of the wide frequency equivalent circuit of the three-phase AC motor based on vector fitting method

Abstract

The prediction of conducted interference in the motor drive system is an important part of the automotive electromagnetic compatibility (EMC) analysis. The accuracy of motor electromagnetic interference (EMI) model directly affects the accuracy of conducted interference prediction. For this purpose, based on the measured data, this paper proposes a broadband equivalent circuit model for three-phase AC motors. The motor is regarded as a single-port network, and its common mode and differential mode impedances are measured. Combining the measured data, a rational function expression is established by the vector fitting method. The influence of different fitting orders is analysed under different parameters, and then an equivalent circuit model of the three-phase AC motor is established. The comparison between simulation and experiment shows that the modelling method is simple, accurate, and highly applicable.