Abstract: A current limiting apparatus includes bridging electrical contacts forming a first current path across a gap in a conductor, a trigger for breaking said first current path in response to an excessive or rapidly changing level of current on said conductor, a fast acting fuse forming a second current path across said gap, for maintaining a conductive path across said gap for a predetermined length of time after breaking of said first current path, to allow the bridging electrical contacts to separate a sufficient distance from said gap to preclude arcing thereacross, and an auxiliary resistor connected across said gap to provide a relatively high resistance conductive path for current in the conductor after said fuse has blown.

Abstract: A hybrid electrical current switching device comprises a triggerable solid-state current switch connected in parallel with a mechanical switch in which the current flow depends on the relative positioning of a liquid metal conducting medium. The solid-state switching device operates as a crowbar switch to mitigate effects of arcing.

Abstract: In the particular embodiments described in the specification a device is provided to protect against failure of a switch connected to a load and to give an alarm that the switch has failed. The device includes a circuit in parallel with the switch which contains a transistor and a diode to cause such voltage drop in the circuit as to prevent current flowing through a second diode when the switch is closed. If the switch fails open, the potential at the load side of the switch will drop, and the second diode will allow current to flow to the load through the circuit. The current flow produces a potential difference across the first diode to turn on another transistor to cause an alarm to be given. The device may be used to test such switches without affecting the load controlled by the switch.

Abstract: An auxiliary thyristor control circuit inserts a zinc oxide varistor in series with the capacitor bank of a static VAR generator for discharging the capacitor bank when the static VAR generator is subjected to high transient voltages.

Abstract: A hybrid power switch for AC voltage in which an SCR switch is in parallel with a mechanical switch. They are operated so that the SCR switch is closed whenever the mechanical switch is to be opened or closed. Circuits are included for closing the hybrid switch when the AC voltage is zero and for opening it when the current is zero.

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: An electrical switch or power controller is provided controlling the application of a source voltage to a load under the control of an electrical command signal, resulting in the development of a load current in response to said electrical command signal comprising: a semiconductor switching means having a predetermined non-bounce switching characteristic, being responsive to a semiconductor switching means operating signal for connecting said load to said voltage, an electromechanical switch means having a low voltage drop in a conducting condition, being responsive to an electromechanical switching means operating signal and being connected in parallel with the semiconductor switching means for connecting the load to the source voltage, control means responsive to the command electrical signal for providing the semiconductor switching means operating signal and the electromechanical switching means operating signal, whereby the semiconductor switching means predetermined non-bounce switching characteristics

Abstract: A DC arc suppression circuit is disclosed for suppressing arcs which occur across a mechanical switch or circuit breaker. Several embodiments are described which employ a bipolar transistor to actively shunt the load current around the mechanical switch when the contacts are opened for a period of time long enough to enable the contacts to be separated by a sufficient distance to prevent arcing. Arcing is prevented when contact bounce occurs upon closure of the contacts, by providing a diode connected in parallel with the base-emitter portion of the circuit which restores the arc suppressing capacity of the circuit almost immediately upon the first closure of the contacts.

Abstract: A hybrid D.C. power controller of the relay/circuit breaker type that uses a hybrid arrangement of hard contacts (4) and power FET's (18, 20) in cooperative functional combination as the arc quenching means for 270 volt D.C. power systems in low atmospheric pressure environments such as at 80,000 feet altitude in aircraft applications. Also, the relay is provided with arc horns (44c, 48b, 48c, 46c), magnetic field amplifiers (60, 62) looped stationary contacts (44, 46), arc splitters (64, 66), and gas ablating insulating members (60b, 62b, 72, 74, 64b, 66) to enable the relay to interrupt the power circuit if necessary without the help of the power FET's. The power FET's are controlled in both opening and closing the power circuit to afford arcless contact operation in normal load make-break situations. Current and voltage sensing (28, 32) and sampling (CS, VS) circuits determine when to turn the power FET's on after contact arcing has provided the required values.

Abstract: The contacts of a power relay are shunted by a gateable semiconductor device to assist in the commutation of contact-destroying arcs upon making and breaking of the power relay contacts; current-detection apparatus, such as a current-sensing transformer and the like, are utilized in the conductors connecting the relay contacts and the gateable switching device to an input from an A.C. source. Control electronics receive the outputs of both current-sensing apparatus to gate the shunting device into conduction during relay contact closure and separation, in a manner to minimize the current passing through the shunting device and therefore to minimize the energy dissipated therein.

Abstract: An arc suppression device (40) for protecting the load carrying contacts (30, 31, 32) of a power contactor (20) includes gate controlled semiconductor devices (TR1, TR2, TR3) connected in parallel with the contacts. A signal from a control circuit (45) causes gating current to be applied to the semiconductor devices nearly simultaneously with the application of current to and removal of current from the solenoid (25) of the power contactor. Circuit means (90) responds to the control signals to provide gating current for a limited period of time prior to, during and following the closing of the contacts. Gating current is not continued after the contacts have closed to protect the semiconductors from possible damage. Additional circuit means (110) responds to the removal of the control signal to provide gating current for a limited period of time prior to, during and following the opening of the contacts.

Abstract: A tap changer voltage regulator permits a tap changer selector contact to engage an open circuited new tap without arcing and has a half-tap voltage auxiliary winding which permits halving the inter-tap voltage to thus double the number of steps, and an auxiliary switch with a pair of movable contacts. A first auxiliary contact initially connects a selector contact which has moved to a new tap through a circulating current limiting resistor to a load, preventing load current interruption. A second auxiliary contact is in series with a normally-closed switch through which load current and circulating current flow. A first set of inverse parallel SCR's is in series with the resistor, while the normally-closed switch is shunted by a second pair of inverse parallel thyristors. The first pair of thyristors is not gated until the first auxiliary contact has attained its new position, precluding initial arcing.

Abstract: A switching circuit having hybrid contactors connects the three output lines of a 3 phase AC power source to three input lines of a load, such as a motor and the like. A single pair of relay contacts is used to directly connect one output line of the AC power source to one input line of the load, whereas each of the other two phases of the AC power source are supplied to the load by one of a pair of pilot relay contacts in series with a diode-shunted one of a pair of master relay contacts. Only two extra pilot relays are used to provide a reversing function. The switching circuit further includes a zero-crossing detector, a phase-sequence detector, a control circuit including four flip-flops arranged in a tumble-down chain and a single distribution circuit having a data select circuit. The control circuit causes the making and breaking of the contacts at particular times, and in a sequence, such that arcing is prevented.

Abstract: A method and circuit for minimizing DC current offset generated by the voltage-integrating property of an inductive load. First, second and third hybrid contactors connect first, second, and third output lines of an AC power source to first, second, and third input lines of an inductive load. Each hybrid contactor includes a pair of relay contacts in parallel with a semiconductor switching unit having two antiparallel-connected silicon-controlled-rectifiers. A latching circuit and several delay circuits are used to turn on and off the hybrid contactors; the timing of the turn-on points is controlled relative to a zero-crossing of a voltage from the AC power source such that minimal DC offset current occurs.

Abstract: A magnetoplasmadynamic switch adapted to be coupled in parallel with an ictive energy storage circuit carrying current through an initially closed circuit interrupter. The switch includes an electrode spaced by a gap from an arcjet source which is triggered by a capacitor. The capacitor is connected to the arcjet source by a closing switch so that a plasma jet is created between the source and the electrode. The voltage on the capacitor is chosen such that the arcjet source current will equal the current in the energy storage circuit at the time when the circuit interrupter has completely opened. The circuit interrupter is opened after the plasma jet is established between the source and the electrode, and the energy storage circuit current is conducted by the magnetoplasmadynamic switch until the dielectric strength of the circuit interrupter reaches a satisfactory level. Another switch is then closed providing a low impedance conduction path parallel to the arcjet source current.

Abstract: A fused short circuit and grounding switch for interconnection in a main circuit, the switch having a switch member operable in one position thereof as a part of the main circuit and operable in another position out of and breaking the normal continuity of the main circuit therethrough and to provide a solid bolted fault, and including an alternate circuit interconnected to and operable to be in parallel with the main circuit, the alternate circuit being fused, the switch being operable to short circuit the alternate circuit and clear the fusing thereof and to thereby interrupt the main circuit on operation of the switch member to the position thereof providing a solid bolted fault.

Abstract: A tap changer voltage regulator permits a tap changer switch selector contact to engage an open-circuited new tap without arcing and has a half-tap voltage auxiliary winding which permits halving the inter-tap voltage and doubling the number of steps, and also has an auxiliary switch system. An auxiliary static switch circuit initially connects a first tap selector in series with a circulating current limiting resistor and a load to prevent load circuit interruption. An auxiliary selector switch initially coupled to a second tap selector and is in series with a normally-closed switch through which the load current and circulative current flow. The normally-closed switch is shunted by a second static switch circuit. The first static switch is not gated until the first tap selector has attained its new position, precluding initial arcing.

Abstract: A commutation circuit for a high voltage DC circuit breaker incorporates a resistor capacitor combination and a charging circuit connected to the main breaker, such that a commutating capacitor is discharged in opposition to the load current to force the current in an arc after breaker opening to zero to facilitate arc interruption. In a particular embodiment, a normally open commutating circuit is connected across the contacts of a main DC circuit breaker to absorb the inductive system energy trapped by breaker opening and to limit recovery voltages to a level tolerable by the commutating circuit components.

Abstract: A switching circuit for selectively coupling a load to an A.C. power source is disclosed. The switching circuit includes a diode-commutated master relay contact and a pilot relay contact coupled in series therewith. The master and pilot relay contacts are coupled between a load and the power source in such a manner that power is applied to the load whenever both the master and pilot relay contacts are closed. A timing and control circuit performs a switching operation to open the master relay contact during a first half-cycle of the A.C. waveform of the power source during which the commutating diode is forward-biased. The pilot relay contact changes state during the next half-cycle of the A.C. waveform and the master relay contact is reclosed during the following half-cycle of the A.C. waveform.

Abstract: A plasma switch comprising a substantially evacuated chamber, a generally tubular cathode disposed within the chamber, an elongated anode disposed concentrically within and projecting from the opposite ends of the cathode, the opposite ends of the cathode being substantially closed by an electrically conductive end plates, at least one of such end plates being electrically insulated from the cathode and from the anode, and circuit means for selectively connecting such end plate to the anode or to the cathode.

Abstract: An improved circuit for energizing and quickly deenergizing the DC operating winding of an electromagnetic relay or contactor from sources of AC supply. It employs a full wave rectifier bridge, a transistor for initiating and maintaining the energization of the relay or contactor control winding when AC is supplied to the bridge, and a zener diode connected in parallel with the main conducting path of the transistor to facilitate quick deenergization of the control winding when the AC supply to the bridge is interrupted.

Abstract: A circuit for suppressing surge or transient currents between a DC power supply and a capacitive load includes a suppression impedance of relatively high impedance connected in series with the load between the DC supply and load, a transistorized control circuit for sensing the voltage across the load, and producing a firing signal when the level of voltage exceeds a predetermined level, and an SCR having its main current path connected in parallel with the suppression impedance, and its gate electrode receptive of the firing signal for turning on the SCR to by-pass the suppression impedance subsequent to application of power to the load.

Abstract: An arc suppression device for protecting the load carrying contacts (25) of a power contactor (15) includes semiconductor devices (TR1, SCR1,SCR2) connectable in parallel with such contacts through an isolation relay (37,61). Gating current to the semiconductor device is applied after the isolation relay is energized and prior to, during and after the power contacts either close or open; but gating current is not continued after the power contacts have closed to protect the semiconductor against damage. Current to the semiconductor is applied before current is applied to or removed from the coil or solenoid (20) of the power contactor. In one embodiment, relays (39,41,43) within the arc suppression circuit (30) control the isolation relay (37), gating current to the semiconductor (TR1) and the coil of the power contactor in the proper sequence. In another embodiment, time delay means (C4-C7,R1) associated with the relays (61,63,65,67) control their sequence of operation.

Abstract: An electrical power supply for an electronic flash unit with a main capacitor charged by a current flowing from a direct-current source through an electrical power source switch to the main capacitor is disclosed. The electrical power source has a semi-conductor switch connected in the charge path to the main capacitor and a detector, arranged to detect whether or not an aerial discharge is produced between the contacts of said switch upon opening of the electrical power source switch, and, upon occurrence of a discharge, to produce a signal. The semi-conductor switch is opened in response to the signal to stop charging of the main capacitor immediately.

Abstract: The present invention relates to a device which is created in such a way that it can close or interrupt an electric alternating current arising on a line at its zero passage. The current mentioned is provided for the feed of energy to a load. The closing or interrupting of the alternating current arising on the line takes place through an activation of an electronic switching means which is switched parallel to a contact that is contained in a mechanical switching means. The contact is in closed position during the load and at the beginning of a short persistence time after the switching in of the electronic switching means and before a brief persistence time before the interruption of the electronic switching means. The switching is instantaneous because the electronic switching means is always activated by a separate energy source.

Abstract: A capacitor and an inductance are connected in parallel with an interruptor disposed in a d-c circuit before the interruptor is mechanically opened. An oscillating current i.sub.o occurs in a circuit composed of the interruptor, the capacitor having a predetermined capacitance and the inductance having a predetermined amount of inductance when the interruptor is mechanically opened. The amplitude of the oscillating current i.sub.o is gradually increased and is superposed on a d-c current I. The interruptor breaks itself when the sum of the d-c current I and the oscillating current i.sub.o across the interruptor reaches zero.

Abstract: A high power a-c circuit breaker having substantially no arcing during interruption consists of two identical switching circuits in series which each include a main high speed switch connected in parallel with a series-connected diode and high speed isolating switch. The diodes of each of the switching circuits oppose one another in polarity. Current flow through the circuit breaker is normally through the closed main high speed switches. A polarity-sensitive operating circuit is provided to open the appropriate high speed switch just before a current zero and to transfer forward current through its related diode. This diode blocks a current reversal, and the associated series-connected isolating switch is opened just after current is commutated into the diode, and at or before the current zero time is reached and while the diode is blocking.

Abstract: A tap changer voltage regulator permits a tap changer switch selector contact to engage an open circuited new tap without arcing and has a half-tap voltage auxiliary winding which permits halving the voltage being interrupted and doubling the number of steps and also has an auxiliary switch with a first movable contact which initially connects the selector contact on the new tap in series with a circulating current limiting inductor and the load to prevent load circuit interruption and is provided with a second movable contact in series with a pair of normally closed contacts through which flow the load current and the current which circulates while the selector contacts bridge adjacent taps during the tap change. The normally closed contacts are shunted by a pair of inverse parallel thyristors.

Abstract: a spark gap device in a high-voltage direct current interrupting device maintains a substantially constant ignition voltage by constructing the spark gap device in at least two series-connected main spark gaps connected in parallel with a voltage divider for distributing the voltage across the main spark gaps. An ignition voltage-determining auxiliary gap is connected in series with an impedance connected in parallel with one or more of the main spark gaps to effect a continued ignition thereof. The ignition voltage of the high-voltage direct current interrupting device is determined by the auxiliary gap such that the auxiliary gap is not subjected to appreciable wear whereby the variations of the ignition voltage are relatively small and not influenced by the wear of the main spark gaps.

Abstract: A thyristor pulse control circuit has a main thyristor, a commutation circuit including a commutating capacitor, and a bypass contactor connected across the main thyristor, and is provided with apparatus for applying a gating signal to the main thyristor immediately before the contacts of the bypass contactor close and also immediately before the contacts of the bypass contactor close to prevent arcing at the contacts. The application of the gating signal is inhibited if a comparison of the voltage across the commutating capacitor with the load current flowing immediately before the bypass contactor closes indicates that the load current is too great to be safely commutated by the commutating capacitor at the measured voltage.

Abstract: The power contactor for controlling the application of power to and the character of the current to a load includes a power relay having contacts connected between a source of power and the load, such as a motor or heater, with each of the contacts being provided with arc suppression means. A steering relay is provided to control the direction of current to a motor and thus its direction of rotation or the voltage applied to a heater. A control circuit insures that the steering relay contacts remain either open or closed while power is being applied to the load. The steering relay is provided with bracer bars to prevent short circuiting between relay contacts should any welding occur therebetween. The arc suppression means for each of the power relay contacts includes a solid state device, such as a triac, in parallel therewith, and auxiliary contacts for controlling the gating current to the triac.

Abstract: High-voltage interconnection circuit-breaker, having connected in parallel, in the first instance a main chamber, having a cut-out power, comprising a rapid functioning on opening and provided for an opening-closing cycle; in the second instance a very rapid closing chamber having a closing power and resistance to overcurrents which lasts a very short time; and in the third instance in series, a resistor and a cut-out chamber for the current reduced by the resistor.

Abstract: The current surge, normally associated with the initial application of a nominal A.C. current to an inductive load, is prevented by preventing the magnetic core of the inductive load from being driven into saturation. Initially, the current is half wave rectified and amplitude limited. The amplitude limitation insures that the core will not be driven into saturation. A voltage detector connected across the inductive load senses only the counter E.M.F. of a polarity opposite to the polarity of the half wave current. When the sensed voltage reaches a predetermined value, a direct connection is provided between the A.C. supply and the inductive load, bypassing the half wave rectifier and the amplitude limiter.

Abstract: A vacuum switch system for interrupting electrolytic cell circuits designed to operate at very high current, relatively low DC voltage. The DC voltage is above the minimum cathode drop potential for the vacuum switch contact material. The system includes plural parallel circuit paths, with one of the parallel circuit paths including at least two serially connected vacuum switches. The operating means for opening and closing all the switch contacts includes means responsive to the opening of the vacuum switches to simultaneously open the serially connected vacuum switches in the parallel path.

Abstract: The invention concerns a system of several circuit-breakers controlling separate circuits fed by the same generator and in which the circuit-breakers are provided with a main cut-out chamber (C.sub.1, C.sub.2) in parallel with a series connection of an auxiliary cut-out chamber (E.sub.1, E.sub.2) and of a resistor (R.sub.1, R.sub.2). An operating sequence opens firstly the main chambers (C.sub.2) of all the circuit-breakers of circuits not affected by a failure, then, successively, the main chamber (C.sub.1) and the auxiliary chamber (E.sub.1) of the circuit-breaker of the circuit affected by the failure, and, lastly, closes the main chambers (C.sub.2) of the circuit-breakers of the circuits not affected by the failure.

Abstract: An A.C. relay system for making and breaking an A.C. power line utilizing an electromagnetic relay having a coil for opening and closing the mechanical switching contacts, a bilateral gated semiconductor such as a triac connected across the contacts, and a control circuit for switching the relay and triac in proper sequence is disclosed. The control circuit comprises a sequence control unit, a phase detector, a triac firing unit and a relay energizing unit. Upon actuation of the sequence control unit, the triac firing unit first fires the triac and then the relay energizing unit energizes the coil to close the mechanical contacts. To break the A.C. power line, the sequence control unit first de-energizes the relay energizing unit and then after a suitable time interval de-energizes the triac firing unit to cut off the gate signal, the triac being turned off when the load current on the power line is below a triac holding current.

Abstract: This circuit breaker comprises a plurality of vacuum interrupters electrically connected in series. The voltage distribution across the interrupters is controlled by a plurality of capacitive circuits respectively connected across the interrupters. Each of these capacitive circuits comprises: (a) the series combination of a relatively large main capacitor and a resistor connected across its associated interrupter, and (b) means comprising a relatively small auxiliary capacitor for producing a high frequency oscillatory current through said associated interrupter upon spark-over of the interrupter, which oscillatory current produces a natural current zero through said associated interrupter and clearance by said associated interrupter at said natural current zero well before said associated main capacitor has had time to fully discharge through said associated sparked-over interrupter.

Abstract: An electrical contactor device includes a solid state arc suppression circuit connected in parallel with main relay contacts. Auxiliary contacts provide gating signals to the arc suppression circuit prior to, during and shortly after the main contacts open. Protection contacts connected in series with the arc suppression circuit are part of a relay which is actuated by additional auxiliary contacts of the main relay. The protection contacts prevent the arc suppression circuit from operating during initial closure of the main contacts thereby allowing the contactor device to be used in those applications where a high in-rush current is expected. A delay circuit holds the protection circuit relay contacts closed after the main relay contacts open to permit operation of the arc suppression circuit; the relay contacts thereafter open to isolate the arc suppression circuit and thereby to prevent any leakage current from flowing therethrough and to prevent any false triggering thereof.

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.

Abstract: The voltage dividing DC circuit breaker comprises serially connected high voltage and low voltage switches to carry load current. Serial capacitors are connected in parallel thereto and a crossed field switching device is connected in parallel to the low voltage switch. When the low voltage and high voltage switches are opened, current is forced through the crossed field switching device. When the crossed field switching device is turned off, the arcing high voltage switch is forced below its chopping current. The open circuit voltage is divided across the capacitors.