A novel filter design approach for mitigating motor terminal overvoltage in long cable PWM drives

Three-phase coupling transmission line equation is derived from the distributed-parameter circuit model and telegraph equation in this paper. According to the theoretical analysis, a novel shunt filter design approach is proposed to mitigate motor terminal overvoltage caused by voltage reflection in pulse width modulation (PWM) inverter-fed AC motor drive systems with long three-phase coupling cable. This approach consists of a method of obtaining the cable´s wave impedance by experiment and a simple and practical simulation approach to investigate the over-voltage phenomena. Based on the simulation model, the motor peak voltage and the shunt filter loss can be both investigated, and then an appropriate filter can be designed. Simulation and experimental results on an induction motor drive system with 50 m cable show the applicability of the filter design approach.