Abstract: A circuit breaker including an overload trip mechanism having a current sensitive element forming a first load current conductive path. The trip mechanism is activated in response to a predetermined level of current through the trip current path. A multiple pole switch unit selectively connects a plurality of shunt load current conductive paths of various resistance values in parallel with the trip current path. The switch is operated by a cam member externally insertable into the circuit breaker in any one of a plurality of camming positions which set the switch unit to provide selected shunt current paths. Removing of the cam from the circuit breaker activates an interlock for automatically tripping the breaker. An alternative embodiment is presented wherein a contact switch unit connects, through a selectable resistance element, a shunt load current conductive path in parallel with the trip current path. The contact switch is activated by a resistance element externally insertable into the circuit breaker.

Abstract: A plurality of single pole breakers, each having a nonconductive housing with parallel sidewalls and mechanically operated release means for actuating the trip mechanism are mounted with the sidewalls of adjacent units in direct contact. A rotatable trip bar extends through the sidewalls and links the release means in each of the units. The outer surface of the sidewalls is recessed around the trip bar opening to form a cavity between adjacent units. A trip lever is positioned in the cavity and attached to the trip bar. A solenoid unit has a mounting flange clamped between the sidewalls with the solenoid plunger engaging the lever to actuate the trip bar and trip the breakers when the solenoid is energized.