Abstract: A time delay undervoltage release for an electric circuit breaker causes the circuit breaker to trip when the control voltage drops below an acceptable level and prevents the breaker from being closed until the control voltage rises to a predetermined level. When the control voltage drops below an acceptable level, the undervoltage release energizes a trip solenoid to trip the breaker. A variable delay is interposed between the control voltage dropping below the acceptable level and the trip solenoid being energized. At the same time the trip solenoid is energized, an inhibit solenoid is deenergized to block the operation of the push-to-close button. When the control voltage increases to a predetermined level, the inhibit solenoid is energized, allowing the push-to-close button to be manually operated and the breaker returned to service.

Abstract: A desensitizing circuit for the electronic fault sensing system of high amperage molded case circuit breaker to prevent a ground fault signal from tripping the breaker in the event of current transformer saturation or the response of a downstream breaker to the ground fault signal.

Abstract: A circuit breaker having an electronic fault sensing and trip initiating unit which provides increased versatility and ability to coordinate the circuit breaker with other interrupting and protective devices in a wide variety of electrical distribution systems. Electronic circuits and components are provided to vary the ampere rating of the breaker, to adjust current carrying capacity, to provide a long time delay trip, a short time delay trip and an instantaneous trip depending on the amplitude of high fault currents, to provide a ground fault trip, to shorten or lengthen the trip time for short time delay faults and for ground faults, and to provide shunt trip capability. The tripping mechanism is magnetic and mechanical, and includes a plunger movable between a trip and non-trip position controlled by an electronic switch in the electronic circuitry, and a toggle mechanism which is unlatched by the plunger when it moves to the trip position.