A recognition method for the coil plunger motion resist force based on coil current in vacuum circuit breaker

Jams in the tripping devices are common faults in circuit breakers, which will lead to the failures in circuit breaker. The resist force of the coil plunger in the tripping device could effectively reveal the jam faults. In this paper, a recognition method for the coil plunger motion resist force based on coil current is proposed. The electromagnetic motion model of the coil is established, and the plunger resist force in VS1-12 is recognized. According to the recognition result and the moving process of the coil plunger, the fitting formula of the resist force is proposed. The resist force from the coil is 5 N, while the force from the latch is 52 N. Based on the fitting formula, the trip coil current of the circuit breaker is simulated. The result is in good agreement with the test result, which verifies the validity of the fitting formula and the recognition method. The method can be applied to the circuit breaker with spring operating mechanism and effectively extract the resist force from the coil current. This research can provide reference for the condition detection and fault warning of coils in circuit breaker. (c) 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.