Multiconductor Transmission Line Approach to Model Common-Mode Currents in Motor-Drive Systems

Common-mode (CM) currents are the main disturbance source generated in motor-drive systems. They may cause electromagnetic interference in vulnerable parts of the system and can even damage the motor. A time-efficient and simple method is presented based on the multiconductor transmission line (MTL) theory to predict the CM currents flowing in each path in the motor-drive system. The focus of this study is to model the motor feeding cables that form the main path of the CM current from the inverter to the motor. Two structures of motor feeding cables are considered and the results from the MTL model of each configuration are compared to its equivalent 3D full-wave simulation in CST. Also, the effect of the length of the cable on the CM current is investigated using the proposed model. The comparison between the presented model and the 3D simulation shows the validity of the model. Moreover, the presented model needs significantly less computation time in comparison with the CST model.