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: A method for interrupting current is provided wherein substantially all current is conveyed through a first current carrying path in a circuit interrupter. A movable element is displaced for interruption of the current, and current is directed through both the first current carrying path and a second current carrying path in parallel with the first path The second current carrying path includes at least one variable or controllable resistance element. Both current carrying paths conduct current during interruption, with resistance of the paths driving the current to a null level. Current through the first current carrying path may be terminated prior to current through the second path. The variable resistance element draws current into the second current carrying path once an arc in the first path reaches a resistance sufficient to transition a portion of the current to both paths.

Abstract: An electromechanical relay including a mechanical displacement electrical contact and a transistor parallel-connected with the electrical contact. The contact is closed for a voltage V corresponding to the forward direction of the transistor and a powering-on of the transistor that starts before the closure of the contact and ends after the closure. The contact is opened for a voltage V corresponding to the forward direction of the transistor and a powering-on of the transistor that starts before the closure of the contact and ends after the closure. Such an electromechanical relay may find particular application to electromechanical switches, hybrid relays.

Abstract: A technique for reducing arc retrogression in a circuit interrupter includes providing a source material in a parallel current carrying path in the interrupter. The source material and parallel current carrying path support no current during normal operation. Upon interruption of a primary current carrying path, current flows through the source material, causing surface ablation of material which enhances the dielectric of the arc plasma, permitting more rapid entry of the arc into a dissipating structure such as a splitter plate stack. The source material transitions to a higher resistance level by heating to limit current flow during interruption.

Abstract: A solid state arc suppression circuitry is defined for placement in parallel extending over the mechanical contacts of a conventional coil and contact mechanical relay mechanism for the purpose of eliminating arcing between the relay contacts which usually occurs immediately prior to closing thereof or immediately after opening thereof. This arc suppression circuitry includes a first circuitry section positioned in parallel with respect to the coil energizing circuit which is activated simultaneously with activating the coil and which is operable through an optical coupling device to activate a second solid state circuit which is positioned extending in parallel with respect to the relay contact to eliminate the transient arching currents thereover during opening and closing of the contacts. The sensing circuit preferably includes a light emitting diode photocoupled to an optotriac for linking operation of the first and second solid state circuits with respect to one another.

Abstract: A technique is provided for forcing greater voltage investment in an arc developed during interruption of a current carrying path. A source element is provided in a secondary current carrying path parallel to a primary path through the device. Upon interruption of the primary current carrying path, an arc is forced to migrate towards a dissipating structure under the influence of an electromagnetic field. The source material then begins to carry current and undergoes surface ablation, releasing gas which is directed towards the migrating arc. The arc is thus caused to expand further, increasing voltage investment and resulting in more rapid extinction and reduction in let-through energy.

Abstract: A circuit breaker includes an opening and closing mechanism section with an opening and closing lever, and an alarm-outputting plate operating in response to a tripping operation. A case for the circuit breaker has a plurality of switch housing sections formed on a top side thereof, in which are installed an auxiliary switch for detecting an ON/OFF state of a main circuit contact and/or an alarm switch for detecting a tripping operation. The opening and closing lever and the alarm-outputting plate have outputting projecting pieces, respectively, laterally spaced apart from each other corresponding to the respective housing sections, for transmitting mechanical output signals to the switches. When the auxiliary and alarm switches are installed, the auxiliary switch is linked to the outputting projecting piece of the opening and closing lever, while the alarm switch is linked to the outputting projecting piece of the alarm-outputting plate.

Abstract: The current-limiting switch (S) has an arc-resistant contact arrangement (K1), which is intended to carry the rated current (IN), of a first switching point (S1), and two commutation paths (P1 and P2) connected in parallel with the first switching point (S1). The first commutation path (P1) contains, in series, a contact arrangement (KT) of a second switching point (ST) and an electronic power switching apparatus (T). The second commutation path (P2) contains, in series, a switching apparatus (SA) and a current-limiting element (RB). The contact arrangements (K1 and KT) are designed to be coaxially symmetrical and are arranged in a pressure-resistant housing (G). Both switching points have electrodynamic drives which open and close very quickly. Thanks to the extremely space-saving, coaxial arrangement of the contact arrangements, undesirable stray inductances can be avoided. This allows the current-limiting switch to be switched on and off very quickly.

Abstract: Hybrid power relay used for opening or closing electrical circuits, including an electrical contact having a mechanical movement, a semiconductor component in parallel with the electrical contact, and a control unit which in response to a logic input level causes the electrical contact to close (open) and the semiconductor component to be turned on. The control unit generates a contact-make signal for closing the contact, and a control signal that turn on the semiconductor component for a predetermined period of time. The control signal prevents the semiconductor component from being turned on after the predetermined period if the electrical contact fails to close so that the semiconductor component is undamaged.

Abstract: A method for interrupting current is provided wherein substantially all current is conveyed through a normal current carrying path in a circuit interrupter. A movable element is displaced for interruption of the current, and a balance is struck between the normal current carrying path and a parallel alternative or transient current carrying path. The transient current carrying path includes at least one variable or controllable resistance element. The transient current carrying path presents a substantially open circuit during normal operation. The variable resistance elements have a lower resistance during initial phases of circuit interruption, favoring transition of all current from the normal current carrying path to the transient path. Thereafter, the variable resistance elements increase in resistivity, producing additional back-EMF to drive the fault current to a zero level and to limit let-through energy.

Abstract: A switching device including a movable contact member. The movable contact member produces an isolating distance and includes an integral semiconductor switching element.

Abstract: A fault current interrupter is provided by the parallel combination of a polymer current limiter 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 polymer current limiter is selected to have a relatively low resistance at quiescent operating currents and a substantially higher resistance at short circuit overcurrents. This allows the current to transfer away from the contacts through the polymer current limiter until the voltage across the voltage dependent resistor causes the voltage dependent resistor to become conductive and thereby transfer the current away from the polymer current limiter.

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: Two molded case electrical switches such as circuit breakers, network protectors, disconnect switches and transfer switches, are secured together side-by-side by joining blocks having tongues extending along their sidewalls which engage undercutting grooves undercutting the irregular surfaces of the confronting sidewalls of the switch molded casings with an interference fit. Separate joining blocks for the front and rear sections of the molded casing are driven into place and retained by bolts engaging flanges on the molded casing. The poles are paralleled by external conductors in any desired configuration so that the standard switches can be used without customization.

Abstract: A protective relay of the type consisting of a relay contacts controlled by means of a relay coil further includes a pair of triacs controlled by an optical switch. The high speed response is attributed to the configuration of the triacs while high ampere rating is provided by the contacts.

Abstract: The device includes two breaking areas formed at each side of a contact bridge carrying main contacts that can be separated from fixed contacts located in the breaking areas and fixed to main conductors. The main conductors each have shaped extensions in the break areas that are configured to cooperate with shaped extensions associated with arc collection parts positioned nearby. The shaping of the extensions and the spacing therebetween encourage a particular direction of arc migration relative to arcs created when the moveable contacts carried by the contact bridge are separated from the fixed contacts. Further, arc migration control is provided in the form of magnetic fields provided in each breaking area. Each arc collection part is connected through a shunt conductor and a single direction of current flow establishing component to make a direct electrical connection to the main conductor associated with the other area.

Abstract: The present invention teaches a variety of filter circuits for protecting against transient electrical pulses such as those caused by electrostatic discharge (ESD) events. One aspect of the present invention teaches an integrated circuit package having primary circuitry, an ESD protection device, a filter circuit, and a conductive lead arranged to couple a point external to the integrated circuit package to a point internal to the integrated circuit package. The ESD device, coupled in series between the conductive lead and a ground reference, can limit the voltage magnitude of a transient electrical pulse occurring upon the conductive lead. The filter circuit is operable such that the voltage magnitude of an electrical signal generated at the filter circuit output is less than the voltage magnitude of the certain transient electrical pulse itself. One preferred filter circuit has two resistors R.sub.1 and R.sub.2, two capacitors C.sub.1 and C.sub.2, and two transistors Q.sub.1 and Q.sub.2.

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 circuit for the protected alternating current power supply of an electrical load, the circuit including, in series, a protective circuit breaker and a bi-directional electronic switch in parallel to which a shunt contactor is connected. An electrical component is connected in series and upstream from the shunt contactor. The electrical component is intended to establish a continuous voltage (V) at the terminals of the electronic switch and its impedance is chosen in such a way that the electronic switch to which command pulses are sent periodically, is made a conductor, when an overload current appears in the circuit and when the contactor is closed.

Abstract: A current interrupter circuit includes a primary current path and a secondary current path in parallel with one another and provided between input and output terminals. At least one solid state switch, preferably a power MOSFET, are interposed along the secondary current path. At least one electromagnetic relay has relay contacts for engaging and disengaging the primary path from a power source and from the secondary path. A sequencing circuit provides a first control signal to turn on or maintain on the solid state switches prior to sending a second control signal to open/close the relay contacts, and further provides a third control signal to turn off the solid state switches shortly after the relay contacts are opened, whereby arcing of the contacts is prevented.

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 current limiting system for a circuit limits current flow through the system. The current limiting system comprises at least one main switch comprising first and second main switch contacts and a contactor connecting the first and second main switch contacts; at least one current limiting device and at least one solid-state switch, which are mechanically unconnected to the main switch, and the at least one current limiting device and least one solid-state switch are arranged in series on a series side of the circuit; the at least one main switch is on a main switch side of the circuit arranged in parallel with the series side; a control that senses a predetermined condition of the circuit, and operably connected with the at least one solid state switch to open and it. Under normal operating conditions, most current flows through the at least one main switch side. When the predetermined condition causes the main switch to open, and the resistance increases in a main switch side.

Abstract: A device/method for actively interrupting fault current in an ac or dc power system before the fault current is capable of growing to peak magnitude or steady state condition, respectively, is presented. In an ac implementation, a commutating capacitance of desired polarity from one of two commutating circuits is coupled across a circuit interrupter comprising a pair of separable contacts. The circuit interrupter operates to open circuit the power system upon reaching zero current therethrough. The commutating capacitance of appropriate polarity actively drives the fault current to zero before the fault current reach peak magnitude, thereby allowing the circuit interrupter to open circuit the power system before the fault current's natural current zero. In dc implementation, the commutating capacitance is connected to dissipate a fault current while the system is in transient state, thereby protecting the power system from full steady state fault current condition.

Abstract: An overcurrent protection system which will give a rapid response to overcurrents which cause a reduction in the voltage across the load, e.g. a partial or complete short across the load, and which will preserve the trip endurance of a PTC device used in the protection system. The new system maintains the trip endurance of the PTC device by removing the source voltage from the PTC, while still keeping the circuit protection arrangement in a fault state, thereby continuing to protect the load.

Abstract: A hybrid power switching device for eliminating mechanical relay arcing. The device reduces mechanical relay contact damage due to arcing and substantially reduces power dissipation by placing a solid state relay in parallel with a mechanical relay. The solid state relay is preferably a semiconductor triac optically coupled to a light emitting diode. The device takes advantage of the inherent lag time (operating time) when a mechanical relay contact switch closes. The device uses only analog components and controls the triac by means of a Schmitt trigger pulse stretcher. The advantages to the present Schmitt trigger include discrete turn off and a narrow hysteresis. A low level control voltage signal operates the mechanical relay and the Schmitt trigger, or optionally a high level control voltage signal in conjunction with a signal inverter.

Abstract: An objective of this invention is to provide a DC circuit breaking device having functions for transmitting direct currents to an electric power system and interrupting direct currents to the electric power system under abnormal conditions such as grounding and short-circuits, where the DC circuit breaking device can minimize the capacity of a condenser for the commuting circuit while rapidly changing the arc voltage to cause arc currents to be quickly extended and vibrated in order to interrupt direct currents in a short arc time. This DC circuit breaking device includes a main DC circuit breaker for interrupting the transmission of direct currents to an electric power system and a DC circuit breaker that is connected in series to the main DC circuit breaker and which is smaller than the main DC circuit breaker.

Abstract: A solid state power switching circuit for alternating current loads, in which operating power for the circuit is diverted from the switched current during power stealing intervals self-synchronized with the alternating current waveform. During periods in which current to the load is commanded, a load current switch is maintained in a low impedance state except for the duration of a short power stealing interval each half-cycle of the supplied alternating current. Self-synchronization is achieved with a current detector which senses whether or not the magnitude of the current diverted during each power stealing interval exceeds a current threshold, and pulse generator logic which shifts the power stealing intervals in time relative to the alternating current waveform in response to the previously sensed current magnitude.

Abstract: Overcurrent protection arrangements including a relay comprising two coils wound on a common magnetic core and a PTC device coupled in parallel with the relay contacts. The arrangement comprises a circuit interruption element which has a normal state which permits the flow of a normal circuit current, I.sub.NORMAL, to pass through the system, and a fault state which permits the flow of at most a reduced current, I.sub.REDUCED, substantially less than I.sub.NORMAL. A first control element is coupled in series between the power supply and the load, and is functionally linked to the circuit interruption element so that when the current through the first control element increases from I.sub.NORMAL to a relatively high current, I.sub.FAULT, the first control element can convert the circuit interruption element into the fault state.

Abstract: A plurality of solid-state switches are provided in parallel with a main circuit switch. A main circuit current is detected by a first current detecting device. A current flowing in each of the plurality of solid-state switches is detected by a second current detecting device. Based on the detected currents of the first and second current detecting devices, the main circuit switch is commanded to open and each solid-state switch is commanded to close by a control circuit, when a fault is detected by a fault detecting circuit. At this point of the process when the main circuit switch is opened, when a commutation anomaly is detected by a commutation detecting circuit, the conducting status of each solid-state switch is maintained. When the commutation achieves a normal status, each solid-state switch is interrupted and circuit breaking, at the point the capability of each solid-state switch is exceeded, is prevented.

Abstract: A hybrid or combination solid state/electromechanical relay circuit combines the advantageous features of solid state and electromechanical relays but avoids their disadvantageous features. An electromechanical relay includes a coil and a pair of contacts which close in response to energization of the relay coil; this pair of contacts being coupled between the load and the ac source. The relay coil is coupled through a switch to a source of dc coil voltage and is also connected to ground. A triac has its first and second main electrodes coupled in parallel to the pair of contacts of the electromechanical relay between the ac source and the load. A capacitor has one lead connected to the first lead of the relay coil and a second lead connected to the gate of the triac. On application of power to the coil, the capacitor charges through the triac, mining it on prior to the coil voltage of the relay reaching its design pick-up voltage. Then during switch dormancy, the coil-energized relay contacts carry the load.

Abstract: A small-sized arrangement for a DC circuit breaker with a reactor and a capacitor connected in series is provided which includes a DC circuit breaker, a parallel impedance means with a suitably determined inductance and a suitable capacitance less in value than the inductance, and an energy-absorbing element. The parallel impedance means has a parallel reactor of a carefully selected inductance and a parallel capacitor of a smaller capacitance value. Determining the inductance and capacitance values of the parallel reactors and parallel capacitors employed in the parallel impedance means to satisfy a certain condition defined by specific formulas can cause the DC circuit breaker to take full advantage of the inherent performance thereof while allowing the interruption time to remain minimized, thereby achieving enhanced interruption performance. Since the capacitance of the parallel capacitor is rendered relatively smaller, the device can be small in size and low in cost.

Abstract: An overcurrent protection system which will give a rapid response to overcurrents which cause a reduction in the voltage across the load, e.g. a partial or complete short across the load, and is particularly suitable for protecting circuits against relatively small overcurrents, comprising: a circuit interruption element which, in the operating circuit, is connected in series between the electrical power supply and the electrical load, and which has (1) a closed state which permits the flow of a normal current, I.sub.NORMAL, through the circuit interruption element, and (2) an open state which permits the flow of at most a reduced current, substantially less than I.sub.NORMAL, through the circuit interruption element; a control element which, in the operating circuit, is connected in parallel with the load, and which has (1)(i) an on state, when the voltage across the control element is a normal voltage, V.sub.

Abstract: An IGBT semiconductor device is connected across switching contacts which are to be protected from arcing. When the contacts are in a normally open configuration, the gate portion of the IGBT is connected to the emitter portion through the contacts, while when the contacts are in a closed configuration, the collector portion of the IGBT is connected to the emitter portion through the contacts. A capacitor is connected in parallel with the gate-collector junction. The combination of the stray collector gate capacitance and the additional capacitor is sufficient to maintain the IGBT device in conduction as the contacts are moving from their closed configuration to their open configuration, thereby preventing arcing across the contacts.

Abstract: A circuit breaker for a distribution system includes a non-self-extinction type semiconductor switch, a current limiting element connected in series to the semiconductor switch for suppressing a fault current. The semiconductor switch and the current limiting element constitute a series circuit. A mechanical type high-speed switch is connected in parallel to the series circuit of the semiconductor switch and the current limiting element. Upon occurrence of a fault in the distribution system, an electric current flowing through the distribution system is commutated to the series circuit from the mechanical type high-speed switch.

Abstract: Substation for the distribution of electrical energy, and protected against arcing faults, characterized by the fact that Hall-effect sensors and additional optical fiber conductors are provided as sensors, whereby the Hall-effect sensors are logically AND linked with the optical fiber conductors.

Abstract: In a relay switching panel, a switching circuit operates to selectively connect and disconnect resistive, capacitive and inductive loads to an AC power source with substantially no arcing. The switching circuit comprises a pair of relays, preferably connected in parallel, with one of such relays having a triac, connected in series therewith. With the relays open, an air gap isolates the power source and the load. In closing the relays in sequence, one relay provides a conductive path from the power source to the triac. After a suitable delay to allow the relay contacts to stabilize in the closed position, the triac is triggered to provide a conductive path from the power source to the load, and a large current surge flows to the load. After the current surge has subsided, the second relay is closed to provide a direct conductive path between the power source and the load. Next the first relay and the triac are removed from the circuit to ensure full conduction through the second relay.

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 load current detection circuit restrains the generation of noise spikes with a minimum of circuitry when changing between current detection sensitivity ranges by providing a plurality of sensitivity resistors between the output of a voltage source, such as a negative feedback voltage amplifier, and a load. Sensitivity range changing is performed via switches that increase or decrease the number of sensitivity resistors between the voltage source and the load. When a current detection sensitivity change is commanded, a voltage difference across the sensitivity resistors is measured, and a control processor generates a control voltage for changing voltage difference gradually until the voltage difference is zero without changing the voltage across the load. The sensitivity range switching then occurs when no current flows through the sensitivity resistors so that no noise spikes are produced.

Abstract: Placed in electrical circuit in shunt of the electrodes that supply current to a protected device and optically coupled to the location in the protected device where an electric arc is most likely to occur, a photosensitive device, responsive to illumination created by such an electric arc, switches to a conductive state, thereby short circuiting the electrodes feeding current to the arc and the arc is quickly extinguished.

Abstract: A high voltage, high current DC switch is shown having a single pole, double throw relay and a solid state power switch such as an IGBT or MOSFET transistor. Voltage is switched by means of the solid state switch while steady state current is conducted through the relay load contact. Several different protector devices are used in the event of circuit malfunction including a combination of thermal and current fuses and resettable thermostats.

Abstract: Semiconductor switching elements (inverse-parallel connected thyristors) of each main circuit element unit are connected in parallel to a main contact of an electromagnetic contactor. An operation input voltage signal applied to an electromagnetic coil of the electromagnetic contactor is detected by an input-voltage detecting circuit of a control section. When the electromagnetic contactor is closed and opened, a one-shot-pulse generating unit outputs a one-shot pulse based on an output of the input-voltage detecting circuit and a signal indicating an opening/closing state of an auxiliary normally-closed contact of the electromagnetic contactor. The semiconductor switching elements are made on only for a short time by a firing circuit based on the one-shot pulse, to turn on and off a load current.

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: A self-contained current limiter unit allows lower short-circuit-rated circuit breakers to be utilized within industrial applications. The unit is electrically-connected in series with the circuit breakers and the protected load to limit the short circuit current to a fixed predetermined value while the circuit breaker trip unit responds to interrupt the circuit current. A single unit can be arranged in electrical series connection with a plurality of lower short-circuit-rated circuit breakers to allow a substantial savings in component and equipment costs.

Abstract: A solid state relay having circuitry incorporated therein which senses line conditions and load conditions and activates an alarm when a fault is detected.

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 electrical switching circuit comprising an electromagnetic relay and a bye directively controlled contactless switch. The electrical switching circuit being able to make and break a capacitive, inductive or pure resistive electrical loads without forming arcs and without substantial heat loss. A control voltage as applied through a phase detecting opticoel coupler to a bye directively controlled contactless switch, such as a triac. The same control voltage is also connected to a time delay circuit wherein the time delay circuit after being charged energizes an electromagnetic relay connecting the load circuit. Upon disconnecting the load the sequence of operation is reversed. The electromagnetic relay is deenergized while the time delay circuit retains the opticoel coupler connection which in turn retains the energization of the contactless switch until the phase of the load energy source to be precisely at the zero voltage crossing at which time the contactless switch is also deenergized.

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 electrical circuit interrupter for connection between two conductors has a first fixed contact electrically directly connected to one of the conductors, a second fixed contact adjacent the first fixed contact, a movable contact electrically directly connected to the other of the conductors, and a positive-temperature-coefficient resistor connected between the first and second fixed contacts. The movable contact is displaceable between a first closed position engaging only the first fixed contact, a second position engaging only the second contact, and an open position engaging neither of the fixed contacts, so that in the first position current can flow between the conductors without passing through the resistor, in the second position current flows through the resistor and current flow is limited thereby, and in the open position current cannot flow between the conductors.

Abstract: Arrangement for arcless interruption of a-c load current in response to a current interruption command. Separable contact means serially connected with controlled impedance means, and parallel connected diversion means are intermediate the a-c source and the load. The controlled impedance comprises field effect transistors (FETs). Since FETs usually have only a single inherent junction, at least a pair of the FETs are oppositely poled so that load current can be cut off notwithstanding the direction of current flow when interruption is commanded. The pair of FETs may be connected back to back. An alternative embodiment has two branch circuits each comprising a FET and a separable contact means. Upon interruption load current is sequentially transferred from one to the other branch circuit and then to the diversion means.

Abstract: A circuit for the protection the contacts of a switch device such as a reed switch when used in a control circuit. The protection circuit isolates the switch contacts from the load it is controlling by establishing parallel electrical current paths between two inputs. Two such parallel paths provide for a symmetrical bi-directional current flow within the protection circuit. Each parallel path contains a controlled switching device which conducts the current in the respective parallel path when the input polarity is in a given direction. The controlled switching device may be controlled from a polarity sensing in the primary branch which contains the switch device. A single parallel path between inputs can be used to provide polarized DC operation. Diodes in the primary path containing the switch device provide for polarity sensing for control of the controlled switch devices in the parallel paths.