Abstract: For use in a trip unit, a transformer assembly is provided in a compact and cost effective form. The assembly includes a toroidal transformer between a pair of busses, and plastic retainers around a conductor which connects the busses. Each of the plastic retainers are molded as a plastic part which features: a flat portion separating the transformer axially from the adjacent bus, a tubular section attached to the flat portion which protrudes through the center of the transformer and serves to separate it radially from the bus, and a set of ribs protruding from the tubular, flat portions which serve to slightly penetrate the insulation material in the center of the transformer and grip the transformer to prevent it from rotating, and a lip protruding from the flat portion which causes the retainer to stop rotational motion relative to the bus.

Abstract: An overtemperature sensing and signaling circuit for electronic trip units includes a voltage divider (16) and a trigger circuit (18). The voltage divider is formed of a first resistor (R1) and a positive coefficient resistor (PT1). The trigger circuit is formed of a first bipolar transistor (Q1) of the PNP-type conductivity and a second bipolar transistor (Q2) of the NPN-type conductivity.

Abstract: A power control relay has a pair of solenoids one of which is briefly energized to open a pair of contacts and the other is opened briefly to close the contacts. A mechanical linkage maintains the contacts in their closed and open positions in the absence of solenoid energization. In a preferred embodiment of the invention, the solenoids drive a cam back and forth between two stable positions. The cam toggles an arm which opens and closes the power switch contacts.

Abstract: A common power supply (20) is often used to provide power for actuating a plurality of circuit breakers (18a-18z) in response to actuation signals from remote control lines (16a-16z). But a large and expensive power supply (20) must be used to deliver enough power to actuate several circuit breakers simultaneously. Moreover, if the circuit breakers (18a-18z) are connected to large electrical loads (21a-21z) and are actuated simultaneously, then the line voltage (V1) will sag substantially. To solve these problems, a time-sharing device (14) enables respective ones of the circuit breakers to respond to their actuation signals only at different times. Preferably, the time-sharing device (14) polls each of the remote control lines (16a-16z) and delivers an actuation signal from each polled remote control line to a preselected number of circuit breakers (21a-21z) which are associated with the polled remote control line.

Abstract: An electronic circuit breaker having a trip solenoid assembly. The trip solenoid assembly includes a permanent magnet, plunger, trip coil and assist coil and is positioned adjacent to a phase conductor. At high current levels the phase conductor generates a flux that may cause the circuit breaker to nuisance trip. An assist coil is wound adjacent the trip coil. The assist coil is energized only when the current through the circuit breaker is of such a level so as to cause nuisance tripping. The assist coil is not energized during that time period when the trip coil is energized.

Abstract: A self-contained test feature for ground fault protection systems in circuit breakers. The ground fault protection system includes a sensing transformer having a primary winding that sums the currents through the phase current transformers. Upon the occurrence of an actual ground fault, the sensing transformer will transmit a signal to cause the breaker to trip. The test feature includes a test transformer having its secondary winding electrically connected in parallel with the primary winding of the sensing transformer. The current path between the test transformer secondary winding and sensing transformer primary winding is completed only upon the activation of a test switch. The primary winding of the test transformer is hooked to an external current source to provide the necessary current to simulate the ground fault.

Abstract: A system for detecting ground faults in circuit breakers having electronic trip units tied together by a low impedance common or circuit ground conductor. A complete electrical path between two circuit breakers is created when the secondary winding of the instrument current transformer of each circuit breaker is grounded as required by National Electrical Code rules. This can cause the ground fault sensing apparatus to inaccurately reflect the ground fault levels of the circuit breakers. The summing transformer of this invention includes a first primary winding which sums the currents through each of the phase current transformers and a second primary winding which indicates the current through the neutral conductor. The second primary is grounded, the ground does not provide a return path for the current between the two breakers since the second primary is isolated from the other summing transformer windings which are electrically connected to the circuit breaker.

Abstract: A flush mounted indicating button assembly and operating button assembly each connected to a cover having a pair of holes which receive identical buttons of the assemblies. Each button includes a circular head portion having a flat top surface and a circular base portion having a lesser diameter than the head portion which has a flat bottom surface and defines a collar portion at the bottom of the head portion. The base portion of each bottom is provided with a circumferential channel adjacent the bottom surface which carries a retaining ring. The indicator button is positioned within the hole by a leaf spring member which is connected to the bottom surface of the cover and includes an opening shaped and dimensioned to permit passage of the base portion while preventing passage of the head portion of the button. The opening is in registration with the hole in the cover and a helical coil encircles the base portion intermediate the leaf spring member and the retaining ring.

Abstract: A rotary switch is provided by a molded knob having a circular top portion, a circular bottom portion and a circumferential flange between the top and bottom portion. The bottom portion includes a recess which is provided with a pair of crush ribs provided to secure a rotary switch pin within the recess. A circumferential channel is provided on the flange around the top portion of the knob with a stop tab provided in the channel. The molded knob is operatively associated with a top plate and a bottom plate, each plate including a plurality of apertures which receive a respective top portion of a molded knob. The bottom plate is provided with an offset portion which spaces the apertures in the bottom plate a predetermined distance from the apertures in the top plate, with dimples provided in the bottom plate to maintain a predetermined spacing of the plates at the locations of the apertures.

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.