Abstract: A molded housing contains a pair of cooperating contacts arranged to be magnetically blown open and an arc chute therefor. The contacts are biased closed and there is no mechanism for manually operating or latching open the contacts. The magnetically blown-open contacts are connected in series with respective poles of a conventional circuit interrupter which also has magnetically blown open contacts but which also has manual operating means and latch means for the contact system.

Abstract: A solid state trip circuit is disclosed which uses a shunt path saturable transformer comprised of a current transformer having a relatively high resistance shunt which serves to apply input voltage to the transformer primary winding. The larger the input current the higher the voltage drop across the shunt and the more quickly the transformer iron will become saturated. The saturation time during each half cycle then produces a measure of the current flow in the primary line. The output of the secondary winding of the transformer as well as a direct but resistive connection from the input circuit lines are applied to a solid state trip circuit which operates a circuit breaker trip latch. Energy for tripping at lower overload current is derived directly from the applied voltage from the line. At high overload conditions however, direct tripping occurs through energy derived from the transformer rather than directly from the line voltage.

Abstract: A blocking attachment to limit movement of a circuit breaker operating handle consists of a single member constructed of material having the resilient properties of sheet steel. Outwardly extending tabs at opposite ends of the attachment are inwardly movable for mounting and dismounting the attachment with respect to a circuit breaker housing. An inverter L-shaped section of the attachment defines a freeway wherein the circuit breaker handle is movable from On to Trip positions and is readily viewable to determine when automatic tripping has taken place. Handle movement is limited to the freeway so that the circuit breaker may not be opened manually while the blocking attachment is operatively mounted to the circuit breaker.

Abstract: A relatively high current capacity molded case circuit breaker having arcing and main contacts and an arc chute to receive and extinguish arcs drawn between the arcing contacts is provided with a trifurcated magnetic arc runner extending from the stationary arcing contact well into the arc chute. The outer sections or legs of the arc runner extend generally parallel to the forward surface of the terminal strap on which the stationary contacts are mounted, and the center leg of the arc runner is curved forward so that the free end of the center leg extends forward of a substantial number of plates in the arc chute. The center leg is shaped so that during opening of the circuit breaker the movable arcing contact moves in close proximity to the center leg and in so doing encourages arcs which may form between the main contacts to extinguish rapidly.

Abstract: A narrow molded case circuit breaker is constructed with a planar cradle having an edge portion to achieve relatching and another edge portion to achieve kicking of the contact arm for weld breaking. A single bonding operation is utilized to connect the movable contact directly to a flexible conductor and at the same time simultaneously secures the movable contact and conductor to the movable contact arm. Since the movable contact is bonded directly to the flexible conductor, the movable contact arm may be constructed of steel or other relatively poor electrical conducting material.

Abstract: A manual motor starter having a current responsive automatic trip means is provided with an undervoltage trip device. The latter includes a solenoid having a plunger biased to operate a lever into tripping engagement with the automatic trip means when the solenoid plunger is magnetically released. While the biasing means is strong enough so that the kinetic energy of the plunger when released from its magnetically held-in position is sufficient to trip the starter, the biasing means is not strong enough to prevent resetting of the trip means after restoration of operating voltage.

Abstract: A multi-pole molded case circuit breaker is provided with an interlock, including a forwardly biased actuator, that automatically operates a common trip bar to trip position when the front cover of the molded case is open. With the cover closed, the actuator Zis accessible for pivoting in a first direction to operate the trip bar to trip position. A single coil spring wound around the actuator is compression loaded to bias the actuator forward and is torsionally loaded to bias the actuator opposed to said first direction.

Abstract: A molded elongated arcuate shield is snap-fitted to a circuit breaker operating handle to achieve a lost motion connection thereto. The operating handle projects through an elongated wall opening in the circuit breaker housing and is movable longitudinally thereof. The shield is disposed between an arcuate interior surface of housing and an arcuate surface of an apron formed integrally with the handle. While the apron above is too short to close the wall opening for all positions of the handle, the apron in cooperation with the shield fully closes the wall opening for all positions of the handle. Latch tabs formed integrally with the shield engage a blocking formation internally of the housing to hold the shield stationary while the handle moves from its On to Trip position. In the former position ON indicia carried by the apron is viewable through an aperture in the shield through which the handle extends, and when the handle is in its Trip position the latched shield blocks the ON indicia from view.

Abstract: This invention relates generally to handle locking attachments for circuit breakers and more particularly relates to handle locking attachments of the kind which receive padlocks.

Abstract: A unitized combination starter is constructed with circuit breaker and contactor sections, each of which is provided with a pair of spaced stationary contacts and a cooperating movable bridging contact. The bridging contacts are closely spaced, are parallel and carry currents which flow in opposite directions. Under severe fault conditions a strong blowoff effect is created to force both bridging contacts in their respective contact opening directions. This quickly places four air gaps in the current path to severely limit current rise and thereby facilitate circuit interruption.