Abstract: A circuit breaker having an automatically adjusting magnetic armature is provided. The magnetic armature includes a spring-biasing means to automatically maintain one end of the armature in the contact with the electromagnet and the other end away from an adjacent electromagnet. The magnetic armature includes a pair of slightly curved arms which are disposed about a pivot guide post. When current through the circuit breaker exceeds a predetermined amount, the end of the armature normally biased away from the adjacent electromagnet is suddenly attracted to the electromagnet. The force from the spring-biasing means is overcome, and the slightly curved arms of the armature pivot about the pivot guide post so that the armature contacts the adjacent electromagnet. A latch holder at the end of the armature becomes disengaged from a latch means to cause the circuit breaker to open.

Abstract: A motor control center of the high voltage type which includes a set of three vertically-disposed cubicles. The two lower cubicles house a pair of contactor assemblies, the lowermost contactor assembly being longer than the upper one. The cubicle enclosing the upper contactor is provided with a partition behind which is a compartment containing vertical bus bars. The lowermost cubicle extends beneath this compartment so that the bus bars drop directly down to engage a set of connectors which are also engaged by the lowermost contactor assembly.

Abstract: An electric distribution panel is constructed with an insulating base formed by extrusion. Also extruded with the base are two rows of circuit breaker mounting ledges, hook formations for each of the mounting ledges to mechanically secure circuit breakers at the load ends thereof, and channel defining formations to slidably receive neutral bars disposed outboard of each of the mounting ledges. A tie bar extends transverse to the neutral bars and provides an electrical connection therebetween. Wiring guide elements are slidably received by appropriate formations of the base and in particular the base is provided with elongated apertures to receive annular embossments of one of the wiring guides elements so as to permit expansion of the base without buckling thereof even though the mounting surface for the distribution device does not expand at the same rate as the base.

Abstract: An improved mechanism for racking a contactor mechanism within an enclosure. The mechanism is urged into a fully-engaged position by an arm extending from a rotatable cross shaft which in turn is operated by a pair of complementary four-bar linkages. The first linkage in effect consists of a handle, connecting rod and bellcrank, the second consisting of the bellcrank and another arm, affixed to the cross shaft. An improved spring-loaded detent arm assists in holding the handle in the "racked on" position and a pivoted interlock engages the bellcrank in two positions.

Abstract: An improved system for sensing current flow in a single phase or polyphase circuit to be protected and deriving a single signal representing composite current flow. A ramp-like reference signal is applied to one input of a comparator at sampling intervals, and the outputs of a plurality of current amplifiers coupled to the other comparator input so that the duration of a change in signal output level of the comparator is an inverse function of composite current. An accumulator stage stores portions of incoming current signals less a predetermined fraction of previous accumulator contents. In the event of circuit interruption the accumulator is decremented in a manner which reflects the inferred thermal history of the system.