Transient over Voltage Due to Switching Operation of Industrial Motor by Vacuum Circuit Breaker and Suppression of Surges

Large industrial establishments like steel plants, cement plants, Paper and pulp industries, refineries and petrochemical industries use high power motors for various operations. The motors are connected through long cables and controlled through vacuum circuit breaker. It has been the experience that several duties of motors such as switching-in and off, abort start, inching, jogging and hunting give rise to high voltage surges at the breaker and motor terminals. Several motors have failed due to the above duties. The present paper reports the occurrence of overvoltage due to switching duties for a given pole to clear factor. The control of switching surges by R-C surge suppressor and its effectiveness are discussed in the paper.