Abstract: A control circuit for reversibly driving a motor from a small d-c voltage. A switched a-c voltage source is selectively applied to the primary windings of either of two voltage step down transformers. The a-c voltage of each secondary winding is rectified and applied to the motor through a series resistor. The rectified voltage from one transformer drives the motor in one direction and the rectified voltage from the other transformer drives the motor in the reverse direction.

Abstract: A reactive current compensator for improving the power factor of a multiphase alternating current electric power circuit comprises a bank of fixed capacitors connected to multiphase line terminals in star circuit relation and two multiphase banks of fixed inductors connected to said terminals in parallel circuit relation, one inductor bank being star-connected and the other being ring connected, together with switching means responsive to a characteristic of power circuit current for controlling the magnitude of current in each phase of both inductor banks.

Abstract: A current differential fault detection circuit. This circuit is used with a plurality of main current transformers respectively coupled to a plurality of separate conductors through which current flows into and out of a sectionalized portion of an a-c electric power system. The secondary windings of the main current transformers are connected in parallel with one another. A normally non-conducting solid state a-c switch is connected in series with the primary winding of an auxiliary transformer and the series combination is connected in parallel with the secondary windings of the main current transformers. Circuit means is provided for sensing the voltage across the secondary windings of the main current transformers. When the secondary winding voltage exceeds a predetermined level the a-c switch is triggered into conduction thereby allowing the fault current to flow through the primary winding of the auxiliary transformer.

Abstract: A circuit responsive to selected symmetrical components of current in a three phase alternating current system. The component values of the circuit can be selected so that the circuit output is proportional only to the negative sequence components of current, only to the positive sequence components, or to both the positive and negative sequence components of current. The positive sequence response is 180.degree. out of phase with the negative sequence response and the amount of positive sequence response can be adjusted without affecting the magnitude or phase of the negative sequence response.

Abstract: A liquid-metal circuit protector comprises two liquid-metal current limiting devices electrically connected in parallel with each other. Each current limiting device comprises a pair of spaced terminals and a passageway extending between said terminals and containing liquid metal. The passageways are hydraulically connected in series in a hydraulic circuit loop. Pumping means operated by current through the protector forces liquid metal around the loop via each of the passageways, and heat exchange means external to the passageways cools the liquid metal during its flow through the loop.

Abstract: A signal amplitude monitor and relay driver circuit. The input signal is applied to a plurality of diodes connected in series with a set of normally closed relay contacts and a first resistor. A second resistor is connected in parallel with the series connected diodes through a set of normally open contacts of the relay. A third resistor is connected in parallel with the combination of the first resistor and normally closed contacts. A transistor circuit is connected with its emitter-base circuit responsive to the signal developed across the first resistor. The transistor output drives an amplifier which energizes the relay coil. When the normally closed contacts are closed the input signal must exceed a first predetermined level before the transistor circuit becomes conductive causing the amplifier to energize the relay coil.

Abstract: Discloses a method of detecting a leak in any one of the vacuum-type circuit interrupters of a high voltage vacuum circuit breaker comprising a plurality of normally series-connected interrupters located within a tank of the circuit breaker containing pressurized gas. Through small openings in the wall of the tank, a first set of conductive rods are inserted to make electrical connection with predetermined terminals of the interrupters. Through other small openings in the tank wall, a second set of conductive rods, insulated from the tank wall, are inserted to make electrical connection with predetermined other terminals of the inrterrupters. These predetermined terminals are such that the interrupters are connected electrically in parallel between the first and second sets of rods.

Abstract: This method of making a ceramic insulator with a stress-grading coating comprises applying to a ceramic body a coating material comprising particles of silicon carbide and a binder comprising a high-silica glass or high-silica glass-forming material, said glass or glass-forming material having a fusion temperature in the range of 1850.degree. F to 2350.degree. F. The coated ceramic body is fired in an argon atmosphere at a temperature in the range of 1850.degree. F to 2350.degree. F to form on the ceramic body a glaze coating that has non-linear resistivity properties.

Abstract: This high voltage circuit breaker comprises a vacuum type interrupter and a fluid-blast type interrupter electrically connected in series and arranged to be opened substantially simultaneously so that concurrent arcing occurs in the two interrupters until about the time a natural current zero is reached. The vacuum interrupter is relied upon to withstand the usual recovery voltage during the initial period after arcing and the fluid-blast interrupter to withstand the recovery voltage after this initial period. Immediately after the circuit has been interrupted by this coaction of the two interrupters, the vacuum interrupter is closed while the fluid blast interrupter remains open, thus relieving the vacuum interrupter of continuing voltage appearing across the circuit breaker.

Abstract: A circuit for monitoring the inductance of an inductive load controlled by phase-operated thyristor devices or similar devices. One embodiment of the invention comprises a first current sensitive device to produce a signal proportional to the current flowing through the load, a voltage sensitive device to produce a signal proportional to the voltage across the load, an inductor driven by the voltage signal and a second current sensitive device for producing a signal proportional to the current flowing through the inductor. The first current signal is then rectified and fed to a voltage divider consisting of five series connected resistors. The second current signal is also rectified and fed to the same voltage divider. A comparator is connected to the aforementioned voltage divider and senses any voltage change on the voltage divider due to a change in the ratio of the second current signal to the first current signal (or the inverse ratio) and thus in effect, senses any change in the impedance of the load.

Abstract: A circuit for triggering a silicon controlled rectifier (SCR) when the voltage across the SCR has a predetermined polarity and exceeds a predetermined magnitude. The anode of a zener diode is connected to the SCR cathode and a resistor is connected between the SCR anode and the zener diode cathode. The voltage at the zener diode cathode acts as a bias for the trigger signal. A silicon unilateral switch responds to the biased trigger signal to trigger the SCR into the conductive state when the biased trigger signal level exceeds the switching voltage of the silicon unilateral switch.

Abstract: An integral shunt capacitor bank connected between high voltage AC terminals and comprising a plurality of serially-connected groups of paralleled capacitors is provided with a dual level overvoltage detection circuit between the paralleling buses defining each capacitor group. Each dual level detection circuit includes a voltage measuring impedance providing a low variable voltage proportional to the voltage to be measured and a pair of voltage responsive circuits across the measuring impedance. The voltage responsive circuits comprising each such pair are responsive to different overvoltage levels and include oppositely poled blocking rectifiers.

Abstract: This electric circuit breaker comprises a plurality of vacuum-type circuit interrupters electrically connected in parallel with each other and means for opening the interrupters substantially simultaneously during circuit interruption. Each interrupter comprises an evacuated envelope and a pair of relatively-movable contacts located within the envelope to provide an inter-contact gap across which arcing can occur during circuit interruption. The stationary contacts of the two interrupters are respectively mounted on stationary contact rods that have their outer ends closely adjacent each other. A communicating passageway extends between the two inter-contact gaps through the stationary contacts and the stationary contact rods for conveying arcing products from any inter-contact gap that is then arcing to any that is not then arcing, thereby promoting concurrent arcing at said gaps during high-current interruptions.

Abstract: This electric circuit breaker comprises a plurality of vacuum-type circuit interrupters electrically connected in parallel with each other and means for opening the interrupters substantially simultaneously during circuit interruption. Each interrupter comprises an evacuated envelope and a pair of relatively-movable contacts located within said envelope that are separable to provide an inter-contact gap across which arcing usually occurs during circuit interruption. The envelope comprises a tubular metal wall portion surrounding the inter-contact gap and a radially-extending opening within this tubular metal wall portion. The metal wall portions of the two interrupters are located in closely adjacent side-by-side relationship, and a short metal tube provides a passage between said openings for conveying arcing products from any inter-contact gap that is then arcing to any that is not then arcing, thereby promoting concurrent arcing at said gaps during high current interruptions.

Abstract: This vacuum-type circuit interrupter comprises a plurality of pairs of separable contacts located within an evacuated envelope and electrically connected in parallel. The movable contact of each pair is mounted on a long, slender contact rod through which current is conducted to and from the associated contact pair. The contact rods, which are also electrically in parallel, are located in side-by-side physical relationship, and each is surrounded by a tube of highly conductive metal such as copper. The tubes are fixed to the interrupter envelope and are located in adjacent side-by-side relationship, thus defining flux-controlling shields around the contact rods in which eddy currents are induced to reduce the magnetic flux penetrating into the interior of each tube from any adjacent contact rod. Means is provided for producing substantially simultaneous contact-separating motion of the contact rods.

Abstract: In an alternating current electric power system subject to rapid load voltage regulation as a result of variations in reactive load current, reactive load current compensation is provided by fixed capacitors and inductors in parallel with the load, the inductors being in series with static switches which are phase controlled to continuously maintain the net reactive compensating current substantially equal and opposite to the reactive component of load current. Compensation control determines firing time of the static switches in accordance with the magnitude of reactive load current and regulating means additionally controls firing time to maintain line current and voltage at a selected line location substantially in phase coincidence.

Abstract: A solid state protective device is disclosed which monitors an electric quantity such as current or its negative phase sequence component in a protected circuit and which responds to abnormal increases in the value of that quantity by activating a circuit breaker or warning device after a period of time which is a non-linear inverse function of the magnitude of the circuit quantity being monitored. The device includes a non-linear function generator, using novel arrangements of operational amplifiers, to approximate the non-linear operating characteristics which are desired and in one form includes an automatic range changing feature to increase the operating range of the device.

Abstract: Reactive current compensating apparatus for a multiphase electric power circuit comprises separately variable reactive impedance elements coupled to the power circuit in multiphase relation through phase shifting means such as a tertiary transformer winding. When phase voltage supplied to the compensating impedance leads or lags the line-to-neutral voltage of the power circuit the compensating effect in respect to negative phase sequence line current components is enhanced as compared to direct conductive connection of compensating impedance to the power circuit.

Abstract: A semiconductor valve type converter for supplying single phase load current at power frequency from an N phase polyphase power system without unbalance of polyphase current or voltage comprises a transformer having KN secondary phase voltages displaced by 180/KN electrical degress (where K is an integer) and a bridge type thyristor network for connecting each secondary phase voltage source alternately to positive and negative network buses. The network buses are connected through a centertapped reactor with the single phase load connected between the reactor tap and the secondary phase voltage sources. A commutating circuit effectively connected across the last thyristor to fire during each positive and negative half cycle of single phase output voltage may be provided if necessary to effect the network reversal of single phase current at each half cycle of power frequency.

Abstract: A cable splice for joining together two or more sections of high voltage cable employs for its primary insulation a rigid, closed-cell foam having a thick integral skin bordering all the external surfaces of the foam and located in regions of the splice where electrical stresses are the highest. The skin has an average density greater than 40 pounds per cubic foot in its outer one-sixteenth inch.