Method of determining contact wear in a trip unit
AssigneeGeneral Electric Company
InventorsJohn J. Dougherty, Bo L. Andersen
Life of this patent
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Abstract
A method of determining contact wear in a trip unit of a circuit breaker and a circuit breaker employing such a method are presented. The trip unit includes a microcontroller and associated memories. An algorithm (program) stored in a memory of the trip unit calculates cumulative energy dissipated in the breaker contacts using the current signal detected at the time of separation. Measurement of cumulative energy dissipated in the breaker contacts is proportional to contact wear. Maintenance setpoints are determined based on industry standard endurance tests and alarm threshold and trip thresholds further based on industry standards are provided within the algorithm for notifying local or remote personnel of a necessary maintenance procedure.
Claims41
A method of detecting contact wear of a pair of separable contacts in an electronic trip unit of a circuit breaker, the method comprising:
- (a) issuing a trip or open signal to initiate a separation of said pair of separable contacts;
- (b) detecting the separation of said pair of separable contacts;
- (c) sensing current through said pair of contacts to provide a sensed current signal indicative thereof;
- and
- (d) integrating the sensed current signal after separation of said pair of separable contacts is detected to result in a first measurement proportional to contact wear of said contacts.
A breaker assembly comprising an electronic trip unit and a circuit breaker having at least one pair of separable contacts, said breaker assembly further comprising:
- means for detecting separation of said at least one pair of separable contacts;
- a current sensor positioned for sensing current through said at least one pair of separable contacts to provide a sensed current signal indicative thereof, and, a signal processor responsive to said first sensed current signal, and having memory for storing signals including program signals defining an executable program, wherein said processor integrates said first sensed current signal to after separation of said at least one pair of separable contacts is detected to result in a first measurement proportional to contact wear of said contacts.
Dependencies are inferred from the claim text.