Abstract: A molded case current limiting circuit interrupter includes a pair of pivoting contact arms each supporting a contact and being connected to wiring terminals such that current flows through the contact arms in opposite directions. One of the contact arms has a movable pivot point. A magnetic drive slot motor device is provided to generate electrodynamic contact opening force upon the contact arms during short circuit conditions. A high-speed magnetic trip device releases the operating mechanism under short circuit conditions to move the arm pivot point before the contact arms reclose. A spring latch may be provided to latch the upper contact arm in a contact-separated position during short circuit conditions until such time as the overcurrent flow through the breaker operates a thermal and magnetic trip mechanism to move an operating mechanism to the tripped position.

Abstract: A ground fault circuit breaker is provided which includes means for sensing ground fault current and for analyzing the waveform of the ground fault current. An operating mechanism automatically separates the contacts of the circuit breaker upon detection of ground fault current waveforms corresponding to the waveform of current passing through human skin. In a preferred embodiment, means are provided to synchronously detect the third harmonic component of ground fault current using phase and amplitude information to determine the presence of a ground fault path through human skin. Alternatively, means are provided to sense peak and average values of ground fault current and to trip the breaker whenever the ratio of peak to average ground fault current exceeds a predetermined level. In another alternative, the slope of the ground fault current at zero crossing is detected and compared to the ground fault current peaks.

Abstract: A circuit interrupter includes two parallel pivoting contact arms, the lower of which is connected to a stationary conductor member using a clinch-type contact. The contact arm has an axle member rigidly attached thereto which is supported by a bearing member attached to the conductor. In one embodiment, the bearing member comprises a pair of bifurcated arms which are clamped about each end of the axle member. In an alternative embodiment, the conductor member lies generally parallel to the lower contact arm and is slotted to form a pair of elongated conductor arms, each of which supports a journal bearing member. One end of the axle is extended through each journal bearing.

Abstract: An automatic transfer control device for generating signals to cause associated circuit interrupters to selectively energize an electrical distribution system from either of a pair of electrical power sources. The device includes an over- and under-frequency monitoring circuit to determine if the power source frequency is within preset limits. The frequency monitoring circuit includes a zero-crossing detector which activates a clock oscillator, the output pulses of which are accumulated by a counter for one half cycle. The number of pulses occurring during the half cycle is compared with a limit value stored in a read-only memory. An alarm signal is activated if the number of pulses accumulated is out of limits.

Abstract: A tripping device for a circuit breaker combines the functions of a current transformer and trip actuator. The device comprises a core member, and an armature disposed in relationship to the core member to establish first and second magnetic circuits. A primary winding carrying load current of an associated circuit interrupter is coupled to the first magnetic circuit and a secondary winding is coupled to the second magnetic circuit, the secondary winding having a temperature dependent switching resistor connected across its output. The armature is movable between normal and trip positions. Low to moderate overloads cause the resistor to heat and switch to a lower resistance, thereby permitting increased current to flow in the secondary winding. This generates magnetic flux opposing the flux produced by the primary winding to lower the net flux in the second magnetic circuit. Magnetic forces on the armature thereby become unbalanced, allowing the armature to move to the trip position.

Abstract: A current limiting circuit breaker includes two parallel pivoting contact arms carrying contacts at the ends thereof. The upper arm is double pivoted and is operated by a mechanism between open and closed positions. A magnetic drive slot motor device surrounds the lower arm and operates during extreme overcurrent conditions to draw the lower arm down and aid in rapidly separating the contacts. An arm positioning assembly is spring loaded to bias the lower arm toward a closed circuit position and provide contact closing force, the upper limit of travel being set by a rod extending through the end of the lower contact arm to abut against the slot motor.

Abstract: A current limiting circuit interrupter comprises a molded case, separable contacts disposed in the case, the contact arms supporting one of the contacts, an operating mechanism connected to the contact arm to move the arm between open and closed positions, and a slotted magnetic drive device generating electrodynamic force on the contact arm during extreme overcurrent conditions to rapidly separate the contacts. The magnetic drive device includes a molded housing forming a slot having insulated walls disposed about the contact arm, and a stack of U-shaped laminations of magnetic material fitted into the housing. The space between opposing walls of the housing is slightly less than the thickness of the lamination stack so that the laminations may be snugly press-fitted into the housing. The housing is then secured to the case in such a manner that the laminations are captured and securely positioned without the need for rivets or other fastening means extending through the lamination stack.

Abstract: An improved bi-switch construction is provided having an interrupting device arranged in electrical parallel relation therewith so that the circuit through each of the two switches is made through the interrupting device, and, subsequently, the interrupting device is shorted out in the closed-circuit position of the particular switch being operated. During the opening operation, again the interrupting device is brought into play so that a parallel electrical path is provided in shunt relationship to the particular switch being operated through the interrupting device, the interrupting switch assuming the burden of interrupting the circuit; and subsequently the particular switch being operated provides an isolating gap from the interrupting device.

Abstract: A molded case current limiting circuit breaker includes separable contacts, an operating mechanism releasable to effect automatic separation of the contacts, and a high speed electromagnetic trip device operable upon overcurrent conditions to release the operating mechanism and separate the contacts. The trip device includes a U-shaped pole piece disposed about a conducting path through the circuit breaker and a movable laminated armature mechanically coupled to the operating mechanism and magnetically coupled to the pole piece. The thickness of the armature is substantially greater than the thickness of the pole piece. During extreme overcurrent conditions electrodynamic force is produced upon the armature by magnetic flux in the pole piece. Upon saturation of the pole piece, force upon the armature continues to increase with increasing current due to electrodynamic force produced between the armature and the conducting path.

Abstract: A circuit interrupter includes an interchangeable trip unit removably disposed in the circuit interrupter housing and connected between a current transformer and a trip mechanism. The trip unit contains electronic circuitry for activating the trip mechanism to open the contacts upon detection of overload current therethrough and includes rejection means provided to ensure that only a trip unit having circuitry compatible with the electrical characteristics of the circuit interrupter can be inserted into the housing. The rejection means comprise a plurality of pins mounted within the housing and extending into the recess to be occupied by the trip unit. The pins are arranged in a pattern unique to all circuit interrupters having identical electrical characteristics. A pattern of holes is provided in the enclosure of the trip unit, the hole pattern being unique to trip units having identical electrical characteristics.

Abstract: A method is provided for testing induction motors, particularly single-phase fractional horsepower motors, which enables routine testing of all motors in production for both starting and running torque and other desired characteristics. The method consists essentially of applying power to the motor for a very short period of time, such as three or four cycles of the supply voltage, then interrupting the power supply and immediately measuring the instantaneous speed by observing the induced voltage from the deenergized motor terminals. The torque then is verified from the change in speed over this short period. Both starting and running torques can be tested very quickly in this manner by means of solid-state control and computing devices, without connecting anything to the motor other than the power leads. Other desired characteristics of the motor can also be readily determined.

Abstract: Apparatus for undervoltage control of a circuit breaker includes a holding coil, a switching transistor connected in series with the holding coil, and a rectifier providing pulsating DC voltage. A level detector responsive to the output voltage of the rectifier produces an actuating signal for the switching transistor when the rectifier output voltage rises above a predetermined value. A switching regulator is provided which is connected to the level detector and the switching transistor for modulating the actuating signal when the voltage to the rectifier input rises above a predetermined value. The switching transistor is thus rendered periodically non-conducting to regulate the average voltage appearing across the holding coil.

Abstract: An adjustable time delay relay is provided which is particularly suitable for automatic transfer switches and other applications requiring a relatively long time delay during periods when electrical power is not available. The relay includes a relay coil connected across a large storage capacitor supplied from an AC power source through a diode.The timing function is provided by a separate timing capacitor which, upon discharge through an associated adjustable resistor, operates a switching transistor to establish a low impedance path across the relay coil, thus discharging the storage capacitor and de-energizing the relay. Such a construction eliminates the need for a close tolerance, high value storage capacitor and provides a high degree of time delay reproducibility despite variations in power supply voltage.

Abstract: An isolated phase bus disconnect switch has a cylindrical aluminum center conductor coaxially disposed within a cylindrical aluminum housing. The center conductor is composed of two fixed axially spaced sections and a coaxial telescoping sleeve assembly which moves axially to make and break electrical contact between the fixed sections. One end of each fixed section and both ends of the sleeve assembly have copper contact rings fixedly attached thereto. Adjoining surfaces of the copper-aluminum interfaces are silver plated, and each of the adjoining aluminum members is axially slotted to permit flexing to allow for differential thermal expansion, while at the same time preventing relative motion between the plated surfaces.

Abstract: An isolated phase bus disconnect switch has a cylindrical center conductor coaxially disposed in a cylindrical conductive housing having an access port. The edges of the port which are perpendicular to the housing have a conductive gasket of tinned copper braid bolted thereto. A curved conductive cover has a rubber gasket attached to its edges. The cover is removably secured to the housing by a plurality of hold-down hinges attached to the housing which supply sufficient pressure to the cover to seal the rubber gasket and produce electrical contact between the cover and the housing. The electrical path from housing to gasket to cover to gasket to housing eliminates the electrical discontinuity caused by the access port, thus preventing destructive electrodynamic forces between the center conductor and the housing.

Abstract: A telescoping disconnect switch for isolated phase bus has a cylindrical movable conductor having a plurality of individual contact assemblies each comprising a contact finger and an axially loaded spring fixedly attached thereto. The contact assemblies are circumferentially arranged about the movable conductor and are removably secured between a contact holder ring and a spring retainer ring. A plurality of stabilizer pads are symmetrically arranged around the circumference of the movable conductor between the contact fingers and are fixedly secured to the movable conductor to stabilize the contact assemblies and align the conductor as it moves to open and close the circuit.

Abstract: A circuit interrupter is provided with a trip unit removably inserted into the housing of circuit interrupter through the cover thereof. The trip unit is secured to the housing by spring clips mounted therein cooperating with recesses in the enclosure of the trip unit to permit insertion of the trip unit with the cover installed but preventing removal of the trip unit without prior removal of the circuit interrupter cover.

Abstract: A circuit interrupter includes an adjustable trip unit for tripping the circuit breaker to the open circuit position upon overload current conditions. The trip unit includes a shorting plug adjuster comprising a pair of connecting pins electrically connected together and insertable into cooperating sockets in the trip unit housing. One of the pins is common to all adjustment positions and is of greater length, having a retaining clip at the end thereof to permit the adjuster to be partially withdrawn, pivoted about the common pin, and inserted into the desired position. The adjuster comprises a flange which covers the trip unit panel socket in all positions, thereby providing protecting against dust and other contamination. The adjuster is cheaper and more reliable than the prior art, providing increased protection against shock, vibration, and contact bounce.

Abstract: A ground fault circuit interrupter includes a differential current transformer sensing winding supplying input to an integrator which is reset to zero at the end of each half-cycle of AC line current. A line-to-ground fault current will cause the integrator output to exceed a predetermined limit value and produce a trip indication. A saturable neutral transformer supplies a voltage to the neutral line and a reference current proportional to the neutral voltage to a comparator. The peak value of the reference current is compared to the peak value of the sensing winding output. A low-resistance neutral-to-ground path causes the sensing winding output to exceed the reference current and a signal to be added to the integrator input, thereby producing a trip indication which energizes an SCR to activate a solenoid.

Abstract: An electrical distribution switchboard including a multiphase horizontal main bus and a multiphase vertical riser bus. Each individual horizontal phase conductor comprises a plurality of spaced parallel bars connected to the corresponding individual vertical phase conductor through an extruded aluminum block having a plurality of grooves formed in each side to receive the spaced parallel bars. The bars are welded in the grooves and the connector welded to the individual vertical phase conductor.