Circuit breaker using bimetal of thermal-magnetic trip to sense current
First Claim
1. A circuit breaker for protecting an ac electrical system from overcurrents and arcing faults comprising:
- separable contacts connected in series with said electrical system;
a trip mechanism opening said separable contacts when actuated;
an overcurrent detector including a bimetal responsive to selected overcurrent conditions in said electrical system for actuating said trip mechanism; and
an arcing fault detector comprising means for sensing voltage across said bimetal representative of current flowing through the bimetal, and arc responsive means actuating said trip mechanism in response to predetermined conditions of said current indicative of an arcing fault.
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Accused Products
Abstract
In a circuit breaker having a thermal-magnetic trip, the voltage across the bimetal is used to sense load currents. This voltage signal representative of current through the bimetal can be used as an input to an arcing fault detector. The signal is converted to a bandwidth limited di/dt signal. If the magnitude of the di/dt signal exceeds a threshold indicative of the onset of an arc a predetermined number of times within a given interval, the circuit breaker is tripped. The voltage across the bimetal can also be used in other devices requiring a measure of load current such as, for example, a meter or an overcurrent alarm.
193 Citations
9 Claims
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1. A circuit breaker for protecting an ac electrical system from overcurrents and arcing faults comprising:
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separable contacts connected in series with said electrical system; a trip mechanism opening said separable contacts when actuated; an overcurrent detector including a bimetal responsive to selected overcurrent conditions in said electrical system for actuating said trip mechanism; and an arcing fault detector comprising means for sensing voltage across said bimetal representative of current flowing through the bimetal, and arc responsive means actuating said trip mechanism in response to predetermined conditions of said current indicative of an arcing fault. - View Dependent Claims (2, 3, 4, 5)
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6. A circuit breaker for protecting an electrical system comprising:
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separable contacts connected in series with said electrical system; a trip mechanism opening said separable contacts when actuated; an overcurrent detector including a bimetal responsive to selected overcurrent conditions in said electrical system for actuating said trip mechanism; and response means comprising means sensing voltage across said bimetal representative of current flowing through said bimetal and means responsive to said voltage. - View Dependent Claims (7, 8, 9)
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Specification