Modeling of common-mode current in motor cable of inverter-fed motor drive system

In some industrial applications, there is a long motor cable connected between the inverter and the induction motor of a motor drive system. However, the common-mode (CM) currents flowing through the cable and motor in the drive systems could bring electromagnetic interferences (EMI) problems to the surrounding electronic devices and shorten the life of motor bearings. It is necessary to study the CM currents in the motor drive systems. In this paper, the high-frequency models of unshielded four-wire power cables are built, the skin and proximity effects as well as the dielectric losses of the cable are taken into consideration. The parameters of power cables are extracted by finite element method (FEM) and validated by measurements. The high- frequency model of the induction motor is also presented and validated in this paper. The CM currents at the motor and inverter terminals are obtained, and the influence of cable length on the CM currents is analyzed.