Circuit breaker responsive to repeated in-rush currents produced by a sputtering arc fault

• US 6,057,997 A
• Filed: 06/03/1999
• Issued: 05/02/2000
• Est. Priority Date: 02/26/1993
• Status: Expired due to Term

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Inventors: Engel, Joseph C., Mackenzie, Raymond W.
• Primary Examiner(s): Leja, Ronald W.
• Application Number:
  US09/324,560
• Time in Patent Office: 334 Days
• Field of Search: 361/45-50
• US Class Current: 361/42
• CPC Class Codes: H02H 1/0015 Using arc detectors
• CPC Class Codes: H02H 1/043 to inrush currents H02H1/046 takes precedence; differential protection of transformers H02H7/045
• CPC Class Codes: H02H 3/335 the main function being self testing of the device
• CPC Class Codes: H02H 3/44 responsive to the rate of change of electrical quantities

Abstract

A circuit breaker responds to sputtering arc faults by counting the times that a bandwidth limited di/dt signal exceeds a threshold magnitude within a selected time interval. In the exemplary circuit breaker, if the threshold is exceeded twice within a one second interval, a trip solenoid is energized. The di/dt sensor can share a sensing coil with a ground fault detector. Alternatively, the resistance of the neutral lead within the circuit breaker is utilized to sense current which is converted to a bandwidth limited di/dt signal for level detection and counting of sputtering arc events.

Claims

1. A circuit breaker for protecting an ac electrical system, said circuit breaker comprising:

a housing;

a set of contacts mounted in said housing;

an electrical conductor connected to said electrical system and to said set of contacts and through which current of said ac electrical system flows;

a current sensor connected across a selected portion of said electrical conductor and utilizing resistivity of said selected portion of said electrical conductor to detect said current flowing through said set of contacts;

trip means connected to said current sensor and generating a trip signal in response to predetermined conditions of said current; and

means opening said set of contacts to interrupt said current flowing in the ac electrical system in response to said trip signal.

2. The circuit breaker of claim 1 wherein said trip means generates said trip signal in response to conditions of said current flowing through said ac electrical system indicative of an arc fault.