Abstract: A solid state circuit interrupter utilizes a power transistor connected across a pair of separable contacts to eliminate contact arcing between the contacts upon circuit interruption. Stored charge is provided to the power transistor prior to contact separation by a separate power supply and control transistor which are immediately turned off after contact separation to turn off the power transistor upon depletion of the stored charge.

Abstract: A gate turn-off thyristor is connected across a pair of separable contacts for diverting the interrupted current first to the thyristor and then to a metal oxide varistor connected across the thyristor. A saturable core current transformer in combination with the capacitance provided by the metal oxide varistor turns on the thyristor when the contacts separate and turns off the thyristor after the contacts have further separated when the core becomes saturated.

Abstract: A fault current interrupter is provided by the parallel combination of a positive temperature coefficient resistor and a voltage dependent resistor connected across a pair of separable contacts to permit the interruption of current without the occurrence of arcing between the contacts when the contacts first become separated. The positive temperature coefficient resistor is selected to have a relatively low resistance at room temperature and a substantially higher resistance at higher temperatures. This allows the current to transfer away from the contacts through the positive temperature coefficient resistor until the voltage across the voltage dependent resistor causes the voltage dependent resistor to become conductive and thereby transfer the current away from the positive temperature coefficient resistor.

Abstract: Disclosed is a circuit breaker comprising an interruptor including a main contact and a series circuit connected in parallel to the main contact and constituted by a breaking resistor and a resistor contact; and an actuator device for performing closing to opening operations of the main contact and the resistor contact; in which the breaking resistor includes a first resistor element and a second resistor element having a resistance value which is smaller than that of the first resistor element; and in which a switching circuit is provided for automatically changing the connection of the first and second resistor elements such that in small capacitive current breaking, an equivalent resistance of the first and second resistor element becomes a large value suitable for the small current breaking, while in short-circuit current breaking, the resultant equivalent resistance becomes a small value for the short-circuit current breaking mainly owing to the resistance value of said second resistor element.

Abstract: An alternating current limiting apparatus is disclosed which includes first, second, and third circuit. The first circuit is formed of a winding means such as transformer, autotransformer, or reactor and a capacitor serially connected to the winding means and is connected between two different kinds of power systems. The second circuit is formed of a series combination of a closing device composed of, e.g. a gap, mechanical or semiconductor switch, or a non-linear resistive element, and a resistor. The second circuit is connected across the output terminals of the winding means. The third circuit is formed of a reactor and a second resistor serially connected to the reactor. The third circuit is connected in parallel with the first circuit. The closing device is normally kept in its open state to form a series resonance circuit of the transformer and the capacitor, thereby directly interconnecting the systems with null impedance therebetween.

Abstract: A foldback power supply (12) is used in an automatic testing device for application of power to a device under test (17). Connection to the device under test is made by means of relay contacts (32, 34, 36, and 38). Arcing and unacceptable transients are avoided by means of a current sink (40) in parallel with the power supply (20). The current sink is operated to draw more than the rated current of the power supply so that the power-supply voltage drops to an acceptable level and the stored energy is simultaneously dissipated. The relay contacts (32, 34, 36, and 38) can then be opened or closed without unacceptably large transients and without the time delays that might otherwise be encountered in waiting for energy dissipation of the energy in the energy-storage elements of the power supply (12) and the device under test (17).

Abstract: An apparatus for the interruption of DC transmission lines without substantial arcing utilizing in combination a DC circuit breaker, a DC-to-AC current converter, converter control and an AC power sink. Upon command from the converter control, DC current is converted to AC current in the current converter and is then magnetically coupled via a transformer into the AC power sink; thus, drawing power out of the DC transmission line and reducing the DC current toward a zero value at which point the DC breaker can be opened without substantial arcing. Various single and multi-phase converter circuits utilizing thyristors are employed. A bypass switch in parallel with the converter can be provided to pass the DC current around the converter during normal operation of the DC transmission line to minimize electrical losses.

Abstract: This electric circuit breaker comprises a main switch and two shunting paths respectively paralleling said main switch, each shunting path containing the series combination of an isolating switch and a diode assembly. The diode assemblies are connected in inverse-parallel relationship with each other. All of the switches are closed when the circuit breaker is closed, and during this interval substantially all current through the circuit breaker is through the main switch. During a circuit-interrupting operation, the three switches are opened. First, the main switch is opened to divert current into one of the shunting paths, and then the isolating switches are opened to complete the interrupting operation with assistance from the diode assemblies.

Abstract: Electrical loads connected to capacitance elements in high voltage direct current systems are protected from damage by capacitance discharge overcurrents by connecting between the capacitance element and the load, a longitudinal inductor comprising a bifilar winding wound about a magnetic core, which forms an incomplete magnetic circuit. A diode is connected across a portion of the bifilar winding which conducts a unidirectional current only. Energy discharged from the capacitance element is stored in the inductor and then dissipated in an L-R circuit including the diode and the coil winding. Multiple high voltage circuits having capacitance elements may be connected to loads through bifilar windings all wound about the aforementioned magnetic core.

Abstract: The negative temperature coefficient effect, which results in destructive current flow above a certain temperature in a semiconductor device is counteracted by a layer of conductive material that has low resistance at normal temperatures but has a positive temperature coefficient that causes its resistance to rise to a high value at temperatures below the certain temperature. The layer is applied to electrodes of semiconductor devices to control current flowing therethrough.

Abstract: A power breaker system comprises a main breaker having a short timing delay function which is connected to a power source; a current limiting circuit for limiting fault current which is connected to the main breaker; and a plurality of branch load circuits consisting of each feeder breaker and each load which are connected to the current limiting circuit.

Abstract: Circuitry for limiting the instantaneous peak current, under fault conditions, of an AC power line, includes a high speed circuit breaker in series with a first capacitor in a main current-carrying branch, which branch is paralleled by two additional branches. According to various embodiments these branches contain various combinations of resistance, capacitance and spark gap elements whereby upon occurrence of the excess fault condition, the high speed circuit breaker opens. Thereafter the voltage buildup across the first series capacitor is sequentially commutated to a second branch having a capacitor and spark gap, with a predetermined arc-over voltage, and subsequently to a third resistive branch. The third branch effectively provides the peak current limiting impedance.

Abstract: Circuit interrupting apparatus for interrupting large direct currents comprising a plurality of parallelly connected branch circuits each including a circuit breaker and a saturable reactor connected in series therewith, and a commutating circuit including a capacitor. When opening the circuit breakers the commutating circuit is connected across the branch circuits to pass commutating current in the direction opposite to the normal load current. When the current decreases below a predetermined value, the saturable reactors desaturate to efficiently interrupt the load current.

Abstract: A polyconductor device is connected in series with a pair of current carrying contacts of a relay switch to delay the current surge through the contacts during the closure thereof. The polyconductor device has a negative temperature-resistance characteristic such that its electrical resistance value at temperatures below a predetermined transition temperature is at least several orders of magnitude larger than its resistance value at temperatures above the transition temperature. When the contacts are initially closed, only a small electric current passes through the polyconductor device which is in its high resistance state. After a predetermined time, the current heats the device to a critical temperature at which time polyconductor device switches to its low resistance state and the current flows essentially unimpeded thereby. During the heat-up time the contacts of the relay switch have completed bouncing and are in a stable, closed condition.

Abstract: The combination of a current limiting device and at least one openable isolating point electrically connected therewith, the current limiting device including a variable, pressure-sensitive solid-state resistance the resistance being variable from an initially relatively very low resistance or impedance value to a relatively very high resistance or impedance value when the isolating point is opened, the solid-state resistance being integrated into the isolating point as a switch contact member.