Abstract: A current limiter providing for a rapid triple series break in the protected circuit. Two movable contact arms are electromagnetically driven apart by two electromagnetic or slot motor drives for rapid circuit interruption when current through the current limiter exceeds a predetermined value. This provides twice the rate of contact separation than that which can be obtained from a single contact arm and consequently increases the rate of arc voltage rise and reduces peak let through current. The magnetic drive devices are formed from a ferromagnetic material and have a narrow slot formed therein, which is magnetically open on one end. Each contact arm is disposed in the slot of an associated magnetic drive device near the open end thereof. Each movable contact arm has a pair of spaced apart contacts mounted thereon. One of these contacts engages a stationary contact and the other contact engages a mating contact on the opposing movable contact arm when the current limiter is closed.

Abstract: A power resistor including a resistance element of metal ribbon formed into an edgewound helix, and an internal three-point support structure axially disposed within the interior of the helix. The support structure includes three insulating assemblies each having a plurality of insulators secured by longitudinal compression springs to a support bar. The support structure also includes a pair of spreaders located at opposite ends of the helix, each having three radially extending arms. Assembly of the resistor includes the steps of inserting the insulating assemblies into the interior of the helix, radially spreading the insulating assemblies against the interior of the helix, and welding the ends of the support bars to the extending arms of the spreaders.

Abstract: An oil filled distribution transformer having a secondary circuit breaker utilizing a cantilevered stationary contact which is engaged by a movable contact for completing a series circuit therethrough. The cantilevered exposed stationary contact, which is surrounded by insulating oil, allows the oil in the transformer to rapidly return to the contact area after circuit interruption providing for faster arc extinction. The movable contact can be a bridging contact which forms a circuit between the cantilevered stationary contact and a second stationary contact mounted above a support base. The movable bridging contact is spring biased toward an open position separated from the stationary contact, but with the circuit breaker in the normally closed position is held in engagement with the stationary contact by a latching mechanism which is responsive to a bimetal or magnetic trip to allow the circuit breaker to trip open during overload conditions. The front cantilevered contact is completely surrounded by oil.

Abstract: A circuit interrupter particularly suitable for use in an oil filled distribution transformer having an elongated contact arm pivotable about one end with a movable contact attached to the other end through suitable insulating members to electrically isolate the movable contact from the elongated contact arm. The movable contact is a bridging contact for completing a series circuit through two stationary contacts. The movable bridging contact is spring biased away from the elongated contact arm. A retainer restricts the movement of the bridging contact away from the insulating members attached to the elongated contact arm. The biasing spring is disposed between the insulating members and the retainer. Grooves formed in the sides of the insulating members restrict rotational movement of the retainer and bridging contact. For larger circuit interrupters, a bridging contact assembly can be utilized having a plurality of parallel bridging contacts and a plurality of biasing springs.

Abstract: A circuit interrupter including a drawout unit mounted within a sealable enclosure and operable between engaged and disengaged positions. A removable conductive safety barrier at ground potential is mounted on the front of the drawout unit and prevents any human contact with components at high potential. An interlock prevents removal of the safety barrier unless the drawout unit is in the fully levered out position. A hinged plate is operated by replacement of the safety barrier to allow the drawout unit to be operated to the engaged position.

Abstract: An enclosed circuit interrupter includes a removable drawout unit mounted within an enclosure and sealed by an enclosure door. The drawout unit is movable between a connected position and a disconnected position by a levering mechanism operated by a levering crank. A shutter prevents insertion of the levering crank unless the circuit interrupter is tripped by actuation of a trip plate. An interlock prevents removal of the inserted levering crank when the drawout unit is at any position intermediate the completely connected and completely disconnected positions. Closing of the enclosure door is prevented when the levering crank is inserted.

Abstract: A power resistor including a resistance element of metal ribbon formed into an edgewound helix, and an internal three-point support structure axially disposed within the interior of the helix. The support structure includes three insulating assemblies each having a plurality of insulators secured by longitudinal compression springs to a support bar. The support structure also includes a pair of spreaders located at opposite ends of the helix, each having three radially extending arms. Assembly of the resistor includes the steps of inserting the insulating assemblies into the interior of the helix, radially spreading the insulating assemblies against the interior of the helix, and welding the ends of the support bars to the extending arms of the spreaders.

Abstract: A circuit interrupter including a multipole circuit breaker and a multipole current-limiting reactor device. The multipole current-limiting reactor device includes an insulating housing forming a plurality of compartments, each compartment having a double-wound solenoid connected in series with one pole of the circuit breaker. The current-limiting reactor device limits the current through the circuit interrupter during overcurrent conditions to a value which can be safely interrupted by the circuit breaker.

Abstract: A circuit interrupter having a magnetic trip element which is integral with the latch. The disclosed circuit interrupter is provided with a bimetal and a magnetic trip element directly connected to the latch of the circuit interrupter which is drawn towards the bimetal, unlatching the circuit interrupter when current flow therethrough exceeds a high overload level. The disclosed circuit interrupter is particularly adaptable for use on a distribution transformer. A movable bridging contact for completing a series circuit between two stationary contacts is provided. The movable bridging contact is spring biased towards an open position separated from the stationary contacts, but with the circuit interrupter in the normally closed position is held in engagement with the stationary contacts by a latching mechanism which is responsive to the bimetal or magnetic trip element to allow the circuit breaker to trip open during overload conditions.

Abstract: A fluid-blast circuit interrupter of the puffer type is provided having two pistons connected in tandem to compress arc-extinguishing fluid in two separate volumes and to produce two separate fluid blasts. Valve action is provided to delay the initiation of the second blast until the interrupter contacts have reached the desired separation distance. By changing component dimensions the degree of compression of arc-extinguishing fluid may be changed without delaying the instant of contact separation.

Abstract: A handle mounted externally on the door of a sealed enclosure operates a mechanism on the inner side of the door which controls the opening and closing of a circuit breaker located within the enclosure. The handle has a detented OPEN and AUTO position and a spring returned CLOSE position. When the handle is in the OPEN position an extensor assembly moves a contact member perpendicularly away from the inner surface of the door to operate a mechanical trip plate of the associated circuit breaker. When the handle is moved to the CLOSE or AUTO position a bumper member is moved by the mechanism in a direction parallel to the inner surface of the door to selectively activate either of two switches located on a switch bracket resiliently mounted upon the associated circuit breaker. The door can be hinged from either side. The handle can be padlocked in the OPEN or AUTO position but not in the CLOSE position.

Abstract: Each section of a three-phase metal enclosed switchgear unit is provided with main through horizontal bus and vertical section bus. The front of each switchgear section is divided into vertically disposed enclosures for housing circuit breakers or circuit interrupting devices. The circuit breakers are mounted close to the vertical section bus with the front of the circuit breaker and the circuit breaker operating handle recessed from the front of the switchgear section. Pan or well-shaped front covers, having a bottom surface flushed with the circuit breaker fit over the front of the vertically disposed enclosures and are mounted to the front of the switchgear section. Different depth wells or pans are used for the front cover, with the depth being determined by the circuit breaker physical size, which is dependent on the breaker rating. The surface of the well flush with the circuit breaker device has a cutout through which the circuit breaker operating handle projects.

Abstract: A network protector includes an automatic circuit breaker mounted in a metal enclosure and a fuse assembly externally mounted upon the enclosure. The fuse assembly includes a fuse housing of molded insulating material and a gasketed access plate providing a watertight enclosure for a fuse. Resiliently mounted studs are provided for connection to a fuse without cracking of the fuse housing due to misalignment between the studs and the fuse.

Abstract: A distribution transformer having a secondary circuit breaker utilizing a movable bridging contact between two stationary contacts for completing a series circuit therethrough. The movable bridging contact is spring biased towards an open position separated from the stationary contacts, but with the circuit breaker in the normally closed position is held in engagement with the stationary contacts by a latching mechanism which is responsive to a bimetal or magnetic trip element to allow the circuit breaker to trip open during overload conditions. The conducting bridging contact completes a series circuit through the circuit breaker which opens during circuit interruption. The secondary circuit breaker can also, if desired, be provided with a signal-light circuit which activates a signal light, on the exterior housing of the transformer, when current through the circuit breaker exceeds a low signal overload value which is less than the trip value.

Abstract: An improved low-voltage circuit-breaker, adaptable for both alternating-current and direct-current is provided having small contact separation, when opened, and a pair of adjoining arcing-rails arranged in generally-parallel relationship, and having only a small gap therebetween of the order of 1/4 inch or less. Preferably, at the ends of the parallel-arranged arcing-rails are a pair of diverging arc-horns, constituting integral extensions of the parallel-arranged arcing-rails, and resulting in considerable elongation of the established arc upon its movement onto the diverging portions of the arcing-rails.

Abstract: A molded case circuit breaker enclosed in a metal cabinet with an openable cover. An operating mechanism has a mounting plate secured to the face of the circuit breaker and a sliding plate movably supported on rollers by the mounting plate at the side of the circuit breaker. A handle mechanism is secured to the sliding plate with a portion extending through an aperture in the cabinet cover. A gasket is disposed between the handle mechanism and the interior of the cabinet cover. The handle mechanism is spring-loaded against the gasket and interior of the cabinet cover to provide a dust-tight seal.

Abstract: A molded case circuit breaker having a solid-state trip unit adjustable over a variety of ratings. One-way adjustment is provided, permitting a reduction in the rating of the circuit breaker and preventing an increase in the rating. A ratchet mechanism and a one-way screw mechanism are provided to implement the one-way adjustment.

Abstract: A circuit is provided for test and operation of indicator lights wherein multiple lights may be tested simultaneously by pushing one button and closing one set of normally open contacts and the individual indicator lights are operated from a circuit utilizing a self-triggering bidirectional thyristor. The test pushbutton and the indicator operating signal circuit operate at a higher voltage, such as 120 volts ac, and the indicator lamp is operated at a low voltage, such as 6 volts ac, providing safety and allowing use of inexpensive incandescent indicator bulbs. One indicator transformer is required for each indicator light. A diode is provided in the test circuit on the high voltage side of each of the indicator transformers to permit a test signal to activate the indicator lamps without affecting the rest of the circuit. The diodes in the test circuit permit only unidirectional current to flow therethrough.

Abstract: A fluid blast circuit interrupter is provided having a pair of compact toroidal-shaped nozzles, steady-state current-carrying contacts, arc-establishing contacts, and a blast valve. A rotatable cam plate provides independent actuation of the steady-state contacts, the arc-establishing contacts, and the blast valve mechanism in a variable and predetermined manner.

Abstract: A molded case circuit breaker is described including a U-shaped thermal and magnetic trip assembly pivotally supported by an insulating housing. A compression spring biases the trip assembly against a releasable cradle which is engaged by a latch. The biasing action of the spring against the pivoting trip assembly maintains a constant latch bite despite warping or other mechanical distortion of the insulating housing.