Abstract: A metal oxide varistor (MOV) is directly electrically connected between a line conductor and ground to dissipate the energy associated with voltage surges appearing on the line conductor. A thermostatic switch, in the form of a resilient arm held in electrical connection with one of the MOV electrodes by low melting point solder, opens in response to a failing MOV to insert a spark gap electrically in series with the MOV. Overvoltage protection is thus maintained, albeit limited to higher level voltage surges.

Abstract: The common trip mechanism of a multi-pole circuit breaker is supplemented by individual breaker pole trip mechanisms operating independently of each other in response to fault current flowing in its breaker pole to unlatch the movable contact arm operating therein for uninhibited, independent opening movement from its closed circuit position to a tripped open position motivated by the electrodynamic forces associated with its breaker pole fault current.

Abstract: A static trip unit is comprised of a current transformer module and an electronic programmer module physically and electrically mated together for incorporation in a molded case industrial circuit breaker. Current transformer modules and programmer modules are separately interchangeable to change breaker current ratings and functional capabilities. A trip interlock is included to prevent breaker closure in the absence of either the trip unit or the trip solenoid.

Abstract: A miniature current limiting circuit breaker incorporates double break circuit interrupting contacts capable of being abruptly separated by a high fault current responsive solenoid acting to first trip the breaker mechanism and then forcibly effect contact separation. The arc chamber is constructed to achieve enhanced blowout of the arc into the arc chute and to develop gas pressures acting to accelerate contact separation. The circuit breaker is trip-free and includes both thermal tripping and internal common tripping capabilities.

Abstract: The secondary winding of a current transformer is driven by a high frequency AC source to excite the core to alternating, uniformly equal positive and negative peaks of current excitation. An inductance sensor alternately senses the secondary winding inductances at corresponding points adjacent the positive and negative peaks of the flux wave generated in the core. Any difference in these inductances is a function of low frequency primary current and is utilized to develop a current flowing through a tertiary core winding to equalize these inductances. This tertiary winding current thus becomes a precise measure of the primary current.

Abstract: In a circuit breaker static trip unit, multiple targets are utilized to indicate which of several possible abnormal current conditions was responsible for precipitating tripping of the breaker contacts to interrupt a distribution circuit. The targets are selectively activated via a common target circuit which includes its own power supply. The target circuit is fail-safe in that failure or malfunction thereof cannot jeopardize tripping of the breaker contacts. Appropriate clamping is utilized to insure that only the selected target is activated.

Abstract: In a circuit breaker static trip unit, a peak detector generates a DC current signal of a magnitude proportional to the rectified peak signal voltage developed across a current transformer burden resistor. The peak detector utilizes a differential amplifier operating in conjunction with a peak signal voltage detecting circuit connected therewith as a negative DC feedback network. A recovery circuit detects the relative amplitudes of consecutive signal voltage peaks pursuant to rapidly adjusting the peak signal voltage detecting circuit to signal voltage peaks of decreasing amplitudes.

Abstract: A low power dissipation power supply utilizes a chopper shunt voltage regulator operating to either direct current transformer developed charging current to storage capacitors when the supply voltage drops below a nominal level or to shunt charging current from the storage capacitors when the supply voltage exceeds the nominal level. Switching of the regulator is controlled by the very small voltage ripple in the regulated supply voltage. In application to a circuit breaker static trip unit, the power supply is equipped to inhibit trip unit functions until the supply voltage is sufficiently up and to limit trip coil actuating current.

Abstract: The secondary currents of plural current transformers are applied to a full-wave rectifying network for developing an overcurrent signal and a ground fault current signal; the latter flowing in a circuit path embraced by the toroidal core of a miniature current transformer. A transformed ground fault current signal appearing in the multi-turn secondary winding thereof is applied to a ground fault trip mode network operating to measure the signal magnitude against an adjustably established, continuous ground fault trip-time curve including a vertical pick-up curve portion and a sloping inverse time (I.sup.2 t) delay portion which terminates in a selected one of plural horizontal, fixed time delay portions pursuant to issuing an appropriately delayed ground fault trip signal. Provisions for zone selective interlocking between upstream and downstream breakers are also described.

Abstract: An overcurrent signal is replicated by current mirrors for joint processing by a long-time trip mode network and a short-time trip mode network pursuant to initiating a circuit breaker trip function after an adjustably predetermined delay predicated on the overcurrent signal magnitude. The former network measures signal against a sloping I.sup.2 t portion of an established trip time curve, while the latter optionally measures the overcurrent signal against a second I.sup.2 t curve portion terminating in a selected one of plural fixed time delay curve portion. Short-time delay zone selective interlocking between upstream and downstream breakers and long-time delay pickup indication are also disclosed.

Abstract: In a busway having plural busbars disposed with their broad sides in face-to-face relation, the ends of longitudinally aligned outside busbars are cut at complementary angles to create a single edge connecting segment for each busbar which extends through a phase transposition zone. Upper and lower transverse connectors are welded at their opposed ends to transversely aligned edge connecting segments to effectively reverse the phase positions of the busbars upstream and downstream of the transposition zone. If the busway includes two inside busbars, phase transposition is achieved in similar fashion. Once insulatively coated, the phase transpositioned busbars are nested together to create a compact transposition zone having a transverse dimension no greater than the busway therebeyond.

Abstract: A spring powered charging mechanism is operatively coupled with a spring powered, circuit breaker contact operating mechanism such that charging of the operating mechanism springs is powered exclusively by the charging mechanism springs as they discharge. The charging mechanism includes a prop controlled by the condition of the operating mechanism to releaseably sustain the charging springs in a fully charged condition, while the operating mechanism includes a hook to releaseably sustain the breaker contacts open against the urgence of fully charged operating mechanism springs. Consequently, the circuit breaker is capable of executing multiple contact opening and closing operations without recharging.

Abstract: A plunger is normally held in a retracted, non-indicating position by a permanent magnet against the force of a spring biasing the plunger to an extended, indicating position protruding through an indicator cap. An electromagnet is selectively energized to develop flux in opposition to the magnet holding flux, whereupon the plunger pops to its indicating position. The cap internally mounts a pair of contacts which are bridged by a plunger mounted shorting ring incident with the plunger assuming its indicating position, thereby completing an external electrical indication circuit.

Abstract: A handle operator slide and a motor operator slide are individually coupled with a charging mechanism to independently charge charging springs thereof. The charging mechanism is operative to charge the springs of a contact operating mechanism as the charging springs discharge. The charging mechanism includes a prop controlled by the condition of the operating mechanism to releasably sustain the charging springs in a fully charged condition, while the operating mechanism includes a hook to releasably sustain the breaker contacts open against the urgence of fully charged operating mechanism springs. Consequently, the circuit breaker is capable of executing multiple contact opening and closing operations without recharging the charging springs by either the handle or the motor via their respective slides.

Abstract: Demonstrator apparatus utilizes a display to portray in log-log coordinate scale the trip-time curve of a solid state (static) trip circuit breaker. A simulated static trip unit programmer is selectively adjustable to vary the shape and position of the displayed trip-time curve. An overlay bearing the trip time-current curve for a prospective upstream or downstream circuit protective device is superimposed on the display and the programmer adjusted to demonstrate selective trip coordination. Alternatively, a pair of simulated trip unit programmers are connected to the display to jointly portray thereon a pair of trip-time curves. Also disclosed is the utilization of a computer to generate on a display plural time-current response curves of a series of circuit protective devices selected on the basis of specific distribution system parameters to provide requisite system protection and response coordination.

Abstract: A circuit for indicating the charge state of a battery supplying discharge current to its load circuit under actual load operation during which battery discharge current is subject to magnitude variations and interruptions, having means for storing a stored signal whose value is representative of battery state-of-charge, means for rapidly increasing the value of the stored signal to the scaled value of the battery terminal voltage when its scaled value is below that of the battery terminal voltage, first means for decreasing the value of the stored signal at a slow rate preestablished such that the stored signal decreases from a first value representative of a fully charged battery to a second value representative of a discharged battery in a time period approximating the average time required during normal operation of the load circuit for the fully charged battery to become discharged, and second means, operative only during intervals when the battery supplies no discharge current to the load, for decreasin

Abstract: A variable drive coupling link assembly is utilized to drivingly couple a rotary motor operator mechanism to a circuit breaker mechanism operator member such as to provide a coasting zone intermediate the end of an operating member charging stroke and the start of an operating member return stroke during which the motor operator mechanism may coast to a stop. The link assembly is structured to abruptly shorten its effective driving length at the conclusion of a charging stroke and to re-establish its full effective driving length by the conclusion of the return stroke, thereby rendering the charging and return strokes of the operator member equal in length.

Abstract: A unique ground fault circuit interrupting (GFCI) device is utilized to control either an industrial circuit breaker or a contactor in protecting a large power distribution circuit against ground faults. The GFCI device is equipped with plural sets of switch contacts which are actuated incident with tripping of the GFCI device. The particular switch contacts are selected to control energization of an actuator adapted to the circuit breaker or contactor, depending on the actuator type. A ground fault sensor responds to ground faults on the distribution circuit by injecting a current imbalancing signal into the GFCI device, causing it to trip. The consequent switch contact actuation initiates operation of the circuit breaker or contactor to interrupt the distribution circuit.

Abstract: A ground fault circuit interrupting (GFCI) device is utilized to control either an industrial circuit breaker or a contactor in protecting a large power distribution circuit against ground faults. The GFCI device is equipped with switch contacts which are actuated incident with tripping of the GFCI device. The switch contacts control energization of an actuator adapted to the circuit breaker or contactor. A ground fault sensor responds to ground faults on the distribution circuit by injecting a current imbalancing signal into the GFCI device, causing it to trip. The consequent switch contact actuation initiates operation of the circuit breaker or contactor to interrupt the distribution circuit.

Abstract: A manually operated mechanism of an industrial circuit breaker utilizes a hook to hold the movable contacts open against the bias of charged mechanism springs. Manual or closing solenoid initiated articulation of the hook releases the contacts for abrupt closure under the urgence of the discharging mechanism springs. An indicator appropriately positioned by the operating mechanism identifies the charged and discharged mechanism states.