Over-voltage suppression with RC-filter networks in multiple drives for long cable drives applications

This paper presents the over-voltages suppression method in multiple PWM drives for long cable applications, using a single RC-filter. The over-voltages at any motor terminals on power bus cable are described by the distributed model. The cable and induction motor models are simulated by ORCAD, thereby providing a convenient method to analyze the over-voltage phenomena. To reduce over-voltages at all motor terminals, the RC-filter is used at the end of power bus feeding cable. The RC-filter design methodologies are mainly discussed in this paper. Three 1/4-hp induction motors are installed on a long cable length of 50, 70 and 90 m respectively. The validity of the proposed design method is supported by simulation results, which are also compared with the experimental results. According to these results, the over-voltages at these motor terminals can be attenuated below 70 % in most cases.