Monitoring of Operating Speed of Electromagnetic Linear Actuator for Vacuum Circuit Breaker by using Search Coil

We present a method to monitor the operating speed of an electromagnetic linear actuator in a vacuum circuit breaker. The induction-voltage waveform is measured with a search coil coupled to the electromagnetic actuator, and this waveform is evaluated to determine the change point, which is used to determine the opening speed. An electromagnetic-motion analysis and experimental testing revealed that the proposed method is effective. This technique could be used to improve condition-based maintenance systems for the vacuum circuit breakers.