Abstract: A snubber circuit of a switching power supply device includes a transistor and a capacitor which are connected in series between a cathode and an anode of a diode, and a secondary winding of a transformer. A vibration voltage is generated in the secondary winding when a surge voltage is generated in the diode. The snubber circuit further includes a differentiating circuit which differentiates a voltage between terminals of the secondary winding, and a peak charging circuit which generates a control voltage of a waveform connecting a plurality of peaks of an output voltage of the differentiating circuit and applies the control voltage to a gate of the transistor to cause the transistor conduct.

Abstract: A system for detecting and controlling temperature of a layered heater is provided that includes a layered heater having in one form a substrate, a first dielectric layer disposed on the substrate, a sensor layer disposed on the first dielectric layer, a second dielectric layer disposed on the sensor layer, a resistive heating layer disposed on the second dielectric layer, and a third dielectric layer disposed on the resistive heating layer. An overtemperature detection circuit is provided in one form that is operatively connected to the resistive heating layer. The circuit includes a resistor, the sensor layer, and an electromechanical relay in parallel with the sensor layer. The sensor layer defines a material having a relatively high TCR and the resistive heating layer defines a material having a relatively low TCR such that a response time of the control system is relatively fast.

Abstract: A power supply apparatus includes a converter to convert AC power into DC power, an SMPS to convert the DC power into DC powers desired by loads, a capacitor to interconnect the converter and the SMPS, a PTC element connected to the converter, a first switch connected in parallel with the PTC element, and a second switch connected in series with the first switch. The method includes turning on the second switch to start charging of the capacitor, turning on the first switch to charge the capacitor to a target voltage level, and turning off both the first switch and second switch if a voltage across the capacitor rises over the target voltage level, to discharge the voltage across the capacitor so as to lower the voltage across the capacitor to the target voltage level or lower.

Abstract: A control system has an instruction path of which an object section connects a microcomputer, a switch and a switch supervisory device with one another. The switch sets the path in conductive or non-conductive state on the low side of the microcomputer. An instruction signal is sent to the microcomputer through the conductive path to set the microcomputer in an operation state. When the device judges based on the operation state of the microcomputer that the switch has set the path in a conductive state, the device sends a first signal of first voltage, causing the signal to have current strength equal to or higher than predetermined value in the path, to the object section. When the device judges that the switch has set the path in a non-conductive state, the device sends a second signal of second voltage lower than first voltage to the object section.

Abstract: A solid state power controller system can include a direct current load, a solid state power controller apparatus including an alternating current sensor coupled to the direct current load, a direct current sensor coupled to the direct current load, a voltage sensor coupled to the direct current load, a main switch coupled to the direct current load via the alternating and direct current sensors, an auxiliary switch coupled in parallel to the main switch, a current limiting resistor coupled in series to the auxiliary switch and a solid state power controller coupled to the main switch, the auxiliary switch, the alternating current sensor, the direct current sensor, and the voltage sensor, and a direct current power source coupled to the solid state power controller apparatus.

Abstract: An arc fault protection circuit and method, provides arc fault protection in a multiphase power system by actuating a plurality of disconnect switches to disconnect the source from the load in response to detecting arcing proximate the load. As well, in response to detecting the arc, a plurality of impedances are introduced into the current path between said source and said load, with each of the impedances increasing the impedance between the source and the load along one phase, prior to the plurality of disconnect switches disconnecting the source from the load.

Abstract: A superconducting magnet assembly comprises a superconducting magnet which, under working conditions, generates a magnetic field in a working volume. The superconducting magnet is connected in parallel with a series combination of a superconducting fault current limiter and a resistor, and with a DC power source. Under working conditions, the magnet can be energized by the power source to generate a desired magnetic field in the working volume.

Abstract: A multiphase current interrupter is provided for interrupting a phase current between two contacts in an electrical phase. The current interrupter includes a first ablative chamber disposed around contacts for a first electrical phase. The first chamber has an ablative material thereon that causes a shock wave when an electrical arc is generated in an arc zone for the first electrical phase during a separation of the contacts therein. The current interrupter further includes at least a second ablative chamber disposed around contacts for at least a second electrical phase. The second chamber has an ablative material thereon that causes a shock wave when an electrical arc is generated in an arc zone for the second electrical phase during a separation of the contacts therein. An interconnecting structure provides fluid communication between the first ablative chamber and the second ablative chamber. The interconnecting structure is adapted to dissipate a shock wave generated in any of the ablative chambers.

Abstract: In an ion bean acceleration system, transient electrical arc suppression and ion beam accelerator biasing circuitry. Two-terminal circuitry, connectable in series, for suppressing arcs by automatically sensing arc conditions and switch from at least a first operating state providing a relatively low resistance electrical pathway for current between source and load terminals to at least a second, relatively high resistance electrical pathway. Selection of circuit component characteristics permits controlling the delay in returning from the second state to the first state after the arc has been suppressed.

Abstract: A non-invasive underground arc fault detection apparatus is for an underground electrical conductor. The apparatus includes an electric circuit having an opening for admitting the electrical conductor therethrough. The electric circuit includes one or two transducers adapted to output a first signal representative of current flowing in the electrical conductor and a second signal. An arc fault detection circuit cooperates with the electric circuit to output a third signal derived from the first signal. The third signal is representative of an arc fault of the electrical conductor. An audible annunciator cooperates with the arc fault detection circuit to annunciate the third signal. A power supply cooperates with the electric circuit and is adapted to power the arc fault detection circuit and the annunciator from the second signal.

Abstract: A power supply in which a feed voltage (Us) is guided through at least one longitudinal branch to at least one output, the at least one branch having a disconnect fuse formed as a controlled semiconductor switch (SW1) and a monitoring unit (UWE) being set up to supply a disconnect signal (s1) to the semiconductor switch when there are changes in voltage or current beyond pre-definable tolerances, in which at least one auxiliary semiconductor switch (H1A), likewise triggered by the monitoring unit (UWE), is connected in parallel to the semiconductor switch (SW1) and in the event of an overload absorbs a substantial portion of the overload current in the branch.

Abstract: A shorting system, which eliminates persistent arcing faults in power distribution equipment, includes a first shorting switch having separable contacts, an actuation input and a fuse electrically connected in series with those contacts. A second shorting switch includes an actuation input and separable contacts, which are electrically connected in parallel with the series combination of the fuse and the first shorting switch contacts. A detection circuit includes one or more arcing light sensors and an actuation circuit. The light sensors detect arcing fault light and the actuation circuit responsively outputs a first trigger signal to the first shorting switch actuation input to close its contacts. For a persistent arcing fault, which is not eliminated by the first shorting switch, a predetermined time after the first trigger signal, the actuation circuit responsively outputs a second trigger signal to the second shorting switch actuation input to close its contacts.

Abstract: The forming of an integrated circuit including at least one element of electronic protection of the circuit formed of at least one switch for short-circuiting supply conductors arranged in a rail, the switch being integrated in the rail, under said conductors.

Abstract: A process control instrument includes a circuit board having a control circuit for generating or receiving a high frequency signal. An antenna includes an electrical conductor. An intrinsic safety circuit couples the control circuit to the antenna and comprises a microstrip transmission line on the circuit board electrically connecting the control circuit to the electrical conductor. A safety stub has a first end electrically connected to the transmission line proximate the electrical conductor and a second end connected to a ground of the control circuit.

Abstract: An electrical circuit interrupter includes a primary or normal current carrying path and a transient or alternative current carrying path. The normal current carrying path is established by a movable spanner extending between stationary contacts during normal operation. The transient current carrying path includes at least one variable resistance element which transitions from a lower resistance to a higher resistance during interruption. The transient current carrying path forms an open circuit in parallel with the normal current carrying path during normal operation. Upon interruption, the transient current carrying path is favored for the fault current, completely interrupting the normal current carrying path. The variable resistance elements increase their resistivity during this phase of operation to aid in providing high levels of back-EMF for complete interruption of fault current through the device and limitation of let-through energy.

Abstract: An overcurrent protection system containing (1) a current sensing means; (2) a first switch coupled to the current sensing means; (3) a voltage sensing means; (4) a PTC device; and (5) a second switch coupled to the voltage sensing means. In one type of system, the second switch is connected in series with a parallel combination of the first switch and the PTC device; and the voltage sensing means is connected in parallel with a series combination of (i) the second switch and (ii) the parallel combination of the first switch and the PTC device. In another type of system, the first switch, the PTC device and the voltage sensing means are connected in parallel with each other; and the second switch (i) is a switch which latches in the open position and (ii) is connected in series with the parallel combination of the first switch, the PTC device and the voltage sensing means.

Abstract: A medium to high voltage load circuit interrupter and method for breaking the flow of electric current in a line having a load and a source. A main switch is connected in series with the line. A metal resistor having a positive temperature coefficient of resistivity (PTC element) is connected in series to the arcing switch, wherein the metal resistor and arcing switch are connected in parallel with the main switch. The main switch moves from the closed position to the open position prior to the arcing switch moving from the closed position to the open position. The circuit interrupter further includes an arc chute having a channel and electrically coupled to the arcing switch wherein the arcing switch is positioned within the channel when the arcing switch is in a closed position. In one embodiment, the PTC element is positioned on an insulator positioned between a ground and the main switch and an arcing switch. In another embodiment, the PTC element is positioned within a channel in the arc chute.

Abstract: A polymer high voltage current limiter comprising, per phase, a fast circuit-breaker pole, a semi-fast protection circuit-breaker pole, and a set of polymer-based elements having very low resistivity, filled with carbon black, and connected in series and in parallel, wherein each element comprises a carbon-filled polymer matrix of elongate shape and including in its interior two parallel metal conductors.

Abstract: An electronic switch circuit for controlling a main circuit including a power source and a load, the electronic switch circuit including (a) an electromagnetic relay device including an electromagnet and at least two contacts, the electromagnetic relay device being connectable in series to the power source and the load of the main circuit; (b) a controlled semiconductor device being a part of the electronic switch circuit; (c) a semiconductor command circuit being connected to the semiconductor device, the semiconductor command circuit serving for controlling the operation of the controlled semiconductor device; (d) a relay command circuit being connected to the electromagnet of the electromagnetic relay device and to the semiconductor command circuit, the relay command circuit serving for controlling the relay device and the semiconductor command circuit; (e) an overload sensor serving for determining a current load flowing through the main circuit and for reporting the relay command circuit of a current ove

Abstract: A current control interface arrangement includes a card circuit and a connector means. The connector means is adapted to generate, from the supply voltage terminals, an enable signal which is directly correlated to the moment of insertion or extraction of the load from the power supply. The card circuit includes an active device to be coupled between a power supply terminal and a load, an enable controlled switch for delivering the correct voltage to the control terminal of the active device for turning on, respectively turning off this device and a time constant means for controlling the rate at which the active device is further rendered conductive. A very simple power supply sequencing apparatus including the current control interface arrangement allows for coupling a plurality of supply voltages to a card in descending order starting from the highest supply voltage to the lowest supply voltage.

Abstract: A Positive Temperature Coefficient Resistivity (PTC) element has a resistivity that increases as the temperature increases. Circuit breakers having PTC elements can achieve better overload and short circuit protection than existing products. Breakers with PTC elements can also be combined with ground fault detection circuits to activate the circuit breaker under ground fault conditions that are less severe than the overcurrent conditions that would normally activate the circuit breaker. A shunt trip assembly incorporating a PTC resistor reduces the required power rating of the clearing switch.

Abstract: A circuit protection system employing arrangements of PTC devices and mechanical switches. The PTC device is not involved in the circuit until a fault is sensed. A current sensing relay senses an overcurrent and directs the current to the PTC device. As the voltage across the PTC device increases, a parallel arrangement of voltage sensing relays completes the operation of the protection system, and disconnects the load until the protection system is reset. The protection system may be reset manually or remotely.

Abstract: An electrical switch arrangement, comprising a first mechanical switch, a second mechanical switch and a PTC device, with (a) the PTC device and second switch connected in parallel and the parallel combination connected in series with the first switch, or (b) the PTC device and first switch connected in series and the series combination connected in parallel with the second switch. The arrangement can interrupt a current and voltage higher than the rated currents and voltages of each of the switches and the PTC devices. The parallel switch can be rated to interrupt the rated interrupt current of the electrical switch arrangement at a voltage below the rated voltage of the electrical switch arrangement, and the series switch can be rated to interrupt a current below the rated interrupt current of the electrical switch arrangement at the rated voltage of the electrical switch arrangement.

Abstract: A circuit for preventing ionization of air between contact points of a DC breaker switch when the breaker switch is opened includes a capacitor connected through a diode to form a shunt between the contact points when the switch is breaker switch is opened. A second switch is operated following shunting of residual voltage on the contact points so as to discharge the capacitor.

Abstract: A circuit embodied within an adapter card for hot-plugging with a card slot in a card slot coupled to a processor based system utilizes a biasing circuit for ensuring that the input voltage to the load of the adapter card is of a sufficient magnitude. The circuit also includes a FET/feedback circuit for opening and closing the circuit provided between the input voltage to the adapter card and the load. This FET/feedback circuit operates as a constant current source to charge the input capacitance of the load and converts to a switched mode when the load capacitance is fully charged. The biasing circuit controls the FET/feedback circuit so that it remains open during hot-plugging of the adapter card into the card slot to alleviate pin arching. A monitor/timer circuit prevents the FET/feedback circuit from operating in the constant-current mode for no longer than a predetermined amount of time.

Abstract: A commutation type DC breaker having a commutation circuit electrically connected in parallel to a main contact. The main contact is connected between a DC power supply and a load. The commutation circuit is a series circuit of a commutation capacitor, a reactor and a commutation switch, with an energy absorption device electrically connected in parallel to the main contact. A switch or a breaker for preventing the flow of commutation current from the commutation circuit to the load in a non-load opening mode is connected between an electrical connection point (P), of the main contact and the commutation circuit, and the load and is opened substantially simultaneously with the opening of the main contact, or before the closure of the commutation switch. In this manner, the safety on the load in the non-load opening mode is enhanced.

Abstract: In a multicircuit control apparatus (10) including a mechanical main contact (125) and plural semiconductor switching devices such as triacs (13a, --, 13d) each connected in series to the main contact, the main contact is closed by a control circuit 15 prior turning-on of any of the semiconductor switching devices and is also opened by the control circuit 15 after completion of turning-off of all the semiconductor devices.

Abstract: An apparatus and method for handling the connection/disconnection transition period of a printed circuit board to an actively empowered backplane which eliminates damaging surge currents and glitches by the use of temporarily functioning field effect transistor circuits which gradiently handle the current loads during the transition period. A set of specifically sized and predetermined lengths of connecting pins on the backplane insures that a programmed sequence of power connection and/or disconnection will occur which permits a group of field effect transistors to gradiently carry the changing current loads that occur during the insertion of the printed circuit board into the backplane. Likewise, during extraction of the printed circuit board from the backplane, the group of FETs (Field Effect Transistors) will carry and buffer the changing current loads from de-stabilizing the power supply source unit.

Abstract: To avoid arcing when the breaker is opened, load current is diverted from a circuit breaker, before it opens, to a pulse forming circuit containing a precharged capacitor and a switch. Load current normally flows from a source of electric power to a load through a network comprising the breaker and a series connected controlled impedance. The pulse forming circuit is connected across the network. When load current is to be interrupted, the switch is closed to discharge a current pulse through the network, and the impedance of the controlled impedance is increased. These actions divert load current from the network to the pulse forming circuit. The breaker is then opened. The voltage across the capacitor first linearly increases from the precharge voltage to zero and then tends to increase in magnitude with an opposite polarity, i.e. that of the source of electric power.

Abstract: An electrical power system protection device includes a circuit breaker and a switch connected in series to a power line. The protection device also has a current limiting element connected in parallel to the circuit breaker. When the level of electrical current flowing in the power line, detected by a current detector, has exceeded a predetermined first set level, a first over-current detector delivers immediately a trip command to the circuit breaker. As a consequence, fault current is commutated to the current limiting element so that any drop of voltage in the power line upstream of the circuit breaker is greatly suppressed. When a state in which a predetermined second set level is exceeded by the detected current level is continued beyond a predetermined period, a second over-current detector delivers an off command to the switch, thus protecting the upstream portion of the power line against the fault in this power line.

Abstract: A device for protecting a principal static relay including semi-conductors from overloads which includes an auxiliary static relay which is connected in series with a conventional parallel protection circuit and whose closure is controlled at the same time as the opening of the principal static relay.

Abstract: An arrangement for forced triggering a spark gap at a voltage below self-ignition voltage, which spark gap is divided into at least two sub spark gaps arranged in series, whereby voltage division components are connected in parallel with the sub spark gaps for effecting voltage division between the sub spark gaps. In order to obtain a forced triggering arrangement which is simple and reliable in operation, an element which is controlled to adopt a high-impedance or low-impedance state is arranged in series with the voltage division components, whereby the element, when adopting the high-impedance state, changes the voltage division between all the spark gaps so that one of the two series connected spark gaps arranged in parallel therewith is ignited.

Abstract: A vacuum circuit breaker particularly suitable for use in an electric motor vehicle. The circuit breaker includes a vacuum interrupter to which a voltage is applied, the series combination of a capacitor and a switch which are connected in parallel with the vacuum interrupter, a provision for charging the capacitor with a voltage opposite the voltage applied to the vacuum interrupter, and a resistance connected in parallel with the vacuum interrupter. The vacuum interrupter, the resistance, and the series combination of the capacitor and switch form oscillation circuit having an oscillation frequency at least 2 KHz and an inductance of at least 1 .mu.H, with a commutating current of at least 5000 A for consuming energy stored in the circuit.

Abstract: A power sequencer for connecting a system to an electrical power supply without powering down the system and without damage to the system or the power supply. A plurality of sequentially engageable contacts are coupled to the power supply for receiving power signals. The contacts are spatially positioned to toggle in a predetermined sequence during engagement. A controller is coupled to the contacts, for supplying a terminal signal to the load in response to the predetermined sequence of toggling of the contacts and in response to the power signals. The controller has a control circuit for generating a control signal which varies in response to the sequence, and a regulator, coupled to the control circuit, for regulating the terminal signal in response to the control signal.

Abstract: A hybrid relay comprising a mechanical relay provided with mechanical contact unit adapted to be actuated by an electromagnet, an electronic relay consisting of a semiconductor device, and a drive switch for supplying a drive current to the electromagnet, wherein the mechanical contact unit comprises: a first contact mechanism for controlling a load current of the hybrid relay; and a second contact mechanism for controlling a control current for a control gate of the semiconductor device; a contact point gap of the first contact mechanism being larger than that of the second contact mechanism. Thus, it is ensured that the first contact mechanism is engaged after the second contact mechanism and is disengaged before the second contact mechanism. Preferably, the mechanical contact unit further comprises a third contact mechanism, for controlling the leak current of the semiconductor device, which may be provided with a delay mechanism for delaying the returning action thereof.

Abstract: The invention relates to an arrangement in an on-load change-over switch of an on-load tap changer for uninterrupted switch-over of the regulating winding of a transformer. On-load change-over switching is usually accomplished using mechanical switching elements. Burning of contact and contamination of oil are disadvantageous. Furthermore, there are known constructions which use a combination of mechanical switching elements and thyristors for on-load change-over switching. The disadvantage of such arrangements is mainly the too great constructional expenditure for the control elements which are liable to breakdown.

Abstract: A shunt device and a method are described for protecting electrical equipment when a fuse blows. The shunt device establishes a by-pass across the fuse for permitting a limited amount of current to begin to flow at a lower voltage than the fuse blowing voltage and before the fuse blows, thereby serving as a transitory relief valve for a portion of the current while minimizing or even substantially eliminating the inductive spike when the fuse blows. The shunt device is made of at least one pyrolyzed polyacrylonitrile (PPP) fiber having a selected switching voltage so that the PPP fiber switches to a low resistance state while the fuse is blowing. When the fuse and PPP characteristics are properly matched, the rate of change of the current with time is lowered, thus selectively decreasing the size of the voltage transients which occur after the fuse blows.

Abstract: A voltage regulator using electronic control of two static switch circuits to permit tap changing without arcing at the switched electrical contacts, without interrupting the load current, and without inducing sizable circulating currents. As a mechanical drive connects a new tap to the auxiliary winding, current through the new winding is blocked by an auxiliary static switch. The drive next opens the main switch delivering current to the load. The opening of the main switch immediately allows the main static switch circuit to "turn on" to prevent arcing and load interruption until the next current zero. The main static switch control senses no current passing through the main switch and ceases gating, and therefore conduction, of the main static switch. Since neither the main static switch nor the auxiliary static switch is conducting current from the auxiliary winding, the load voltage begins dropping and the voltage across the auxiliary static switch begins rising.

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 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: A printed circuit board connection system provides multiple voltage level interconnection to each individual printed circuit board of a multiple board system via a common circuit board connector mounted on a backplane. Power supply and logic signals at each required voltage level are supplied to electrically isolated regions of the backplane, and are then connected via edge connectors to process control circuits on the respective printed circuit boards. A circuit board extraction handle includes an automatic disabling switch actuator to facilitate circuit board maintenance while power is on.

Abstract: Electrical equipment protection apparatus is provided comprising a plurality of varistor devices connected mutually in parallel, each of which exhibits a non-linear characteristic with an inherent differential in such characteristics, in combination with current sharing elements comprising a plurality of positive temperature coefficient resistors respectively associated with each of the non-linear resistors to ensure substantially equal current sharing among the plurality of varistors.

Abstract: A voltage snubber connected to the output terminals of a transistorized, push-pull inverter for supplying bidirectional current to an inductive load comprises a snubber capacitor and relatively large valued resistor connected in series with each other across the output terminals of the inverter and a switching circuit for bypassing the resistor during turn-off periods of the inverter transistors. The value of the snubber resistor is high enough to provide slow recharging of the snubber capacitor during turn-on periods of the inverter transistors to reduce transistor power dissipation. When the resistor is bypassed by the switching circuit during the inverter transistor turn-off periods, the snubber is gated on to suppress high voltage surges generated by the inductive load. The snubber switching circuit is responsive to current sensors or logic commands connected in circuit with the inverter to detect turn-off transistors of the inverter transistors.

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 circuit card is disclosed of the type for connection to a system by means of connector pins on the card. The circuit card includes a soft power switch for reducing the power transient effects of inserting the card by gradually coupling the circuit load on the card to the system power supply voltage. Connector pins of various extensions are used to initiate events in the coupling of the circuit load to the power supply voltage. The card further includes logic which causes the circuit load to be gradually decoupled from the power supply upon removal of the card from the system.

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: 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: 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: 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.