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.

Abstract: According to one aspect of the invention, it comprises a fireproof enclosure having a first and a second electrical terminal. The first electrical terminal is coupled to an electrical contact internal the fireproof enclosure. An actuating member is provided in the trip mechanism. A first end is inside the mechanism, while a second end extends outside. The actuator member is biased to have the first end in contact to the electrical contact at a first position. The first end has a bimetallic latch coupled thereto. The bimetallic latch comprises a contact portion at the point of coupling to the first end and a first and second wing portion extending from the contact portion. Ledges are disposed on the interior of the trip mechanism. The wing portions engage the ledges to hold the actuator member at a second position. The second position establishes a gap between the electrical contact and the contact portion of the bimetallic latch.