Abstract: A load protecting circuit includes a triac connected in series with the load to provide an open circuit when a voltage drop or current surge is applied to the load. The triac is gated through a transistorized gating circuit which includes a zero-crossing detector so that the gate of the triac is turned on or off only during zero-crossing points of the AC line voltage. The gating circuit is responsive to a voltage drop detector comprising a photo-optical isolator which turns off as the voltage drop in the input line drops below a predetermined value and, thus, turns off the gating current to the triac. The current surge protector comprises a transistor of reverse polarity from the transistors contained in the gating circuit so that a gate current derived from the current surge and applied to the transistor turns off the activating current for the gating circuit. The device also includes a varistor for protection against spike voltage impulses and a radio frequency suppression line.

Abstract: An automatic electronic reset current cut-off protection circuit for electrostatic precipitator air cleaner power supplies of the type utilizing a ferroresonant transformer having a primary winding, a secondary winding for producing relatively high voltage and a tertiary winding for producing a relatively low voltage. The circuit operates to inhibit power supply operation in the event of an overload in the ionizer or collector cell by sensing a voltage derived from the high voltage and comparing the sense voltage with a fixed reference. When the sense voltage falls below a predetermined value, current through the transformer primary is inhibited for a predetermined time. Current flow is automatically reinstated and the circuit will cyclically cause the power supply to shut down until the fault has cleared. The reference voltage is derived from the tertiary winding voltage resulting in increased sensitivity of the circuit to short duration overload conditions.

Abstract: Electrical apparatus to monitor electrical three-phase power includes circuitry to protect three-phase equipment from excessive variations in line voltage, phase to phase unbalance, and reverse phase sequencing; to protect personnel against automatic restart of equipment at return of line power; and protect power sources against overload at return of line power, after power interruptions.

Abstract: There is disclosed apparatus for detecting phase unbalance in a 3-phase electric power system and initiating protective shutdown for motors or other loads in the system which includes a 3-phase rectifier, a peak voltage measuring circuit, a comparison circuit for comparing each phase maximum with a predetermined proportion of the peak voltage and generating a pulse whenever a phase maximum exceeds the predetermined proportion of the peak voltage, a missing-pulse detection circuit receiving the pulses, a fault circuit producing a fault signal in response to a signal from the missing-pulse circuit, a delay circuit responsive to the fault circuit and a visual indicator and relay for indicating a persistent phase unbalance fault and initiating protective action.

Abstract: This concerns an undervoltage relay device for a circuit breaker system with a time delay feature. Two lines of the electrical system to be protected are monitored by a transformer. The output of which is rectified and provided to a capacitive element which, among other things, filters the signal. The capacitive element may comprise a single capacitor or combination of capacitors. The combination chosen is the function of the amount of time delay desired. If the voltage across the monitor lines drops below a predetermined value, the voltage level across the capacitive element begins to drop accordingly. This decreasing voltage signal is provided by way of a voltage divider to one input terminal of a comparator. The other input terminal of which is maintained at a reference voltage. When the signal voltage drops below the reference voltage, the comparator shift state thus causing an undervoltage relay coil to be deenergized.

Abstract: A computer power/temperature protector is provided. A control and disconnect circuit is responsive to a power interruption to disconnect power from a computer to which the protector unit is connected in-line, and thereafter responsive to a reset signal to connect power to the computer. A power interruption is obtained automatically when a voltage failure occurs on the power cable to the computer. A thermostatic switch also automatically interrupts power when the ambient temperature of the room in which the computer or other load is located exceeds an adjustable pre-set level. A power emergency disconnect switch is provided for manually interrupting power. Furthermore, the present invention provides at least one varistor for shunting transient voltages. The varistors are automatically connected to the power lines of the cable when the apparatus is manually reset to supply power to the computer.

Abstract: A device for protection against power failures, having a programmable current source with two levels, which are controlled by a threshold detector, the current from the source being large at high voltages and reduced at low voltages.

Abstract: In a preferred embodiment, designed for gas-efficient automobiles having low power alternators having insufficient power and utilizing a battery of insufficient voltage to operate both the automobile necessary circuitry and heater as to heat the automobile space within a satisfactory short time interval of a few minutes, a circuitry of conventional type but additionally including in series with a low voltage relay, another voltage relay switch which when energized turns on current to an electromagnetic relay normally open switch to close the switch to thereby connect a second battery positive terminal to the output terminal of the alternator for thereby recharging the second battery, and the normally open switch normally connecting the positive terminal of the second battery to a large supplemental heater when the normally open switch is in an open state, whereby when the regular low capacity battery is at low voltage the supplemental heater quickly heats the automobile space, and at elevated voltage the conv

Abstract: A high voltage monitor and display for electrostatic precipitators producing a digital output code representing the magnitude of the high voltage associated with the ionizer and collecting cells which is applied to a series of display elements arranged in a spaced linear relationship such that the number of adjacent display elements illuminated corresponds to the magnitude of the high voltage to provide a visible indication of ionizer cell and collector cell performance. A predetermined minimum cell voltage is established digitally, and the high voltage power supply inhibited when the high voltage falls below the predetermined value. Alarm means are also provided for indicating when the collector cell or ionizer cell voltage is below the predetermined operating minimum.

Abstract: A voltage monitoring and indicating circuit for producing an output pulse at an output terminal in response to the loss of a positive dc input voltage at an input terminal. A capacitor is charged during the presence of an input voltage at the input terminal, and a transistor coupled to the capacitor and to the output terminal operates in a non-conducting state so that no voltage pulse is produced by the transistor at the output terminal. In the event of a subsequent loss of the input voltage, the capacitor discharges into the transistor and causes the transistor to operate in a conducting state and a discharge path to be provided through the transistor for the capacitor. As the discharge takes place, an exponentially-decaying pulse is produced by the transistor at the output terminal.

Abstract: A power source device for electronic counting systems comprising an a.c. power source, a first d.c. power circuit connected to the a.c. power source for supplying an object detecting device with a d.c. power, a second d.c. power circuit connected to the a.c. power source for supplying a counter with a d.c. power, the rate of discharge of the first d.c. power circuit being less than that of the second d.c. power circuit so as to prevent the counter from receiving signal from the detecting device during power failure of the a.c. power source.

Abstract: A circuit is described for protecting a semiconductor junction device such as a transistor against damage from high voltage transients that can be produced by kinescope arcing in a television receiver. The protected device is coupled to a circuit point at which the transients can appear. The protection circuit comprises a normally nonconductive protection transistor with a collector coupled to a source of operating potential, a base coupled to a source of threshold conduction bias reference voltage, and an emitter connected to the circuit point at which high voltage transients are likely to appear. The base bias of the protection transistor is determinable independent of the bias of the protected device, and the protection circuit is connected to the protected device with substantially zero voltage offset between the circuit point and the protected device.

Abstract: A power supply sequencing apparatus utilizing a pair of MOS-FET devices to simultaneously apply or remove the positive and negative power supply sources to an electronic unit.

Abstract: An electronic tuning type receiver comprises a digital-to-analog conversion section having a memory adapted to store a digital input value obtained by counting pulses generated by a manual operation. In one embodiment an up-down counter is also employed. A digital-to-analog conversion process section generates a pulse signal having a number of pulses per unit time corresponding to an output of the memory or counter and a tuning section receives as a tuning signal, an analog output signal of the digital-to-analog conversion section. The receiver further comprises an electric source "off" state detecting circuit which, in one embodiment only when both of the outputs of the digital-to-analog conversion process section and an electric source thereof are brought to be in "off" state, operates to suspend the operations of relevant sections of the receiver. In another embodiment the up-down counter and pulse oscillator are suspended when the power is switched off.

Abstract: A protection circuit is provided in which the output voltage is sensed and the output device is shut-off for protection when the output voltage falls below a predetermined trip voltage. The monolithic integrated circuit includes a voltage shifting circuit for transferring the output voltage to a biasing circuit which biases a switching circuit which turns the line driver off, when an overload or short circuit causes a voltage drop below a predetermined trip voltage. The protection circuit is disabled during start-up or signal rise time by splitting the input signal into two separate paths in which the signals have different delays. The shorter delay allowing the input signal to rise and to appear on the output line before the longer delay input signal rises enabling the protection circuit.

Abstract: A switching mode power supply provides a D.C. output voltage having a value related to the duty cycle of the supply's controlled oscillator produced signal. The inventive shutdown circuit inhibits operation of the supply if the duty cycle increases to a value indicative of failure of the supply to produce a minimum desired output voltage. Operation of the supply is inhibited for a predetermined shutdown interval following which a restart cycle deactivates the shutdown circuit for a period to allow the supply to attempt to establish its desired output.

Abstract: An electronic sensing circuit monitoring the voltage on each of two alternating current power lines indicates when a load may be transferred from one of the power lines to the other without generating undesirable transient voltages or currents in the load.

Abstract: A system is disclosed for switching a load between two ac sources wherein no degree of synchronization therebetween is required and wherein the switching is accomplished with the use of two electro-mechanical relays each having a three pole, double throw contact arrangement. Furthermore, this load switching is accomplished without the production of any interpower currents between the two sources.

Abstract: A battery monitoring circuit in a programmable controller generates a logic signal when it senses a low output voltage from a memory back-up battery. A controller processor is programmed to set a fault status bit and store it in a memory with input/output status data. The fault status bit is output to an I/O interface rack together with input/output status data during an I/O scan routine. The fault status bit generates a logic signal to a fault indicating device on the I/O interface rack to signal an under-energized memory battery in the controller processor.

Abstract: A power line disturbance (PLD) detector circuit includes a digital counter which is driven by pulses provided by a clock in an associated data processing system. The PLD detector circuit includes a comparator amplifier for comparing primary AC power to a DC reference voltage on a cycle-by-cycle basis. The amplifier generates a reset pulse once during each AC cycle as long as the AC voltage exceeds the DC reference voltage. When a decoder circuit detects a count outside the range of counts attained by the digital counter between normally occurring reset pulses, the decoder circuit responds by generating a PLD signal. The PLD signal is provided both to the associated data processing system and to a Power On Reset circuit. The Power On Reset circuit is initialized by the PLD signal, permitting the circuit to respond consistently upon subsequent restoration of power.

Abstract: A switchgear assembly which includes a vacuum interrupter, a current transformer, and a capacitive voltage sensor, all embedded within a cast epoxy housing mounted to a solidly grounded support structure. The voltage sensor includes a first capacitor, which is formed by an interrupter conductor stud, a plate, and the cast epoxy disposed therebetween, and a second capacitor, which is connected between the plate and a metal tube extending outside the housing. The tube is connected to ground through a conductive coating, applied to the housing, having an impedance which is very low in comparison to the impedance of the first capacitor.

Abstract: A three phase undervoltage monitor separately converts the voltage on each phase to a D.C. voltage, compares each of the separate D.C. voltages with a reference voltage, and operates an output signal whenever one or more of the voltages drops below the reference voltage.

Abstract: An output circuit for a programmable sequence controller wherein a load drive element control circuit is responsive to a command signal stored in a memory circuit for controlling a load drive element connected between a load and a first electric supply. Between a power input terminal of the load drive element control circuit and a second electric supply, there is connected in series a switching element, which is switched on in response to a signal applied from a supply voltage detecting circuit only when the voltage level of the second electric supply is not lower than a level sufficient for normal and reliable operation of the load drive element control circuit.

Abstract: An electric control system is provided for a motor vehicle which automatically disconnects electric loads from the battery of the vehicle when the vehicle is not in use, and in the event that the driver leaves the vehicle without turning off the headlights, radio, or other accessories. The control system is connected to the battery of the vehicle, as well as to the generator and to the ignition switch. The system senses excess current from the battery under conditions when the generator is not functioning and when the ignition is turned off. However, a particular current threshold is established, so the system will not respond to normal current drain, such as from electric clocks, and the like. Also, a predetermined time delay is built into the system, so that the headlights, and other accessories will not be turned off the moment the driver stops his vehicle and turns off the ignition.

Abstract: Disclosed herein is a protection circuit for a power amplifier. The protection circuit comprises a current detecting section for detecting a level of a load current of the power amplifier, a voltage detecting section for detecting a level of a load voltage across a load, an AND-gate circuit responsive to outputs of the current detecting section and the voltage detecting section for detecting a short-circuit of the load, and a control section responsive to an output of the AND-gate circuit for disconnecting the load from the amplifier.

Abstract: Disclosed herein is a direct current motor control circuit adapted for connection to first and second supply terminals of DC power source and to a DC motor connected between the positive and negative terminals of a DC power source, the control circuit including a solenoid including a solenoid coil having one end connected to the first supply terminal and having an opposite end, and having a pair of solenoid contacts connected in series relation with the DC motor between the positive and negative terminals and which close to energize the DC motor when current flows through the solenoid coil.

Abstract: Apparatus for undervoltage control of a circuit breaker includes a holding coil, a switching transistor connected in series with the holding coil, and a rectifier providing pulsating DC voltage. A level detector responsive to the output voltage of the rectifier produces an actuating signal for the switching transistor when the rectifier output voltage rises above a predetermined value. A switching regulator is provided which is connected to the level detector and the switching transistor for modulating the actuating signal when the voltage to the rectifier input rises above a predetermined value. The switching transistor is thus rendered periodically non-conducting to regulate the average voltage appearing across the holding coil.

Abstract: A regulation circuit for providing timing gate signals to the dc power section of a power supply, the regulation circuit utilizing phase angle conduction of a programmable unijunction transistor. The conduction angle is determined by the occurrence of the cycles of the ac source voltage unless earlier conduction is determined by the sensed dc voltage. Early conduction occurs when the control voltage to the PUT is allowed to build up beyond a predetermined level when the sensed dc voltage is low. When the sensed dc voltage is high, an electronic switch closes to discharge a storage element to prevent control voltage build up and, hence, early conduction. When there is an ac source voltage outage, a diode connected to the control voltage output conducts to keep the control voltage to zero and hence closing of the electronic switch to prevent undue regulation of the power section output at such times and to permit storage capacitors therein to maintain a dc output until source voltage is reestablished.

Abstract: A phase unbalance detecting system that includes also low-voltage detection and wrong-phase-sequence detection. The system can be packaged in a small volume because it is a solid state type that uses a minimum of electronics and does not require transformers for obtaining signals from the several phases of the plural-phase power line but only one transformer for the D.C. power supply circuit for the detection system. The system incorporates means for allowing it to be used at 50 or 60 Hz without separate adjustment, for making it insensitive to noise and harmonics of the power line, and for providing a good estimate of the negative sequence voltage caused by a phase unbalance. It provides external terminals whereby it can be adapted for use at different power line voltages.

Abstract: DC control voltage derived from the system voltage activates a first relay to apply the control voltage across a dropping resistor and an undervoltage release (UVR) solenoid, thereby holding the UVR solenoid in while the system voltage remains above a minimum level. An energy storage RC network holds the UVR solenoid in for momentary drops in system voltage. In the event of a protracted system undervoltage condition, the first relay drops out to drop out the UVR solenoid and trip a system circuit breaker. When nominal system voltage is restored, the control voltage activates the first relay and, via an RC charging circuit, temporarily actuates a second relay to switch out the dropping resistor, thereby temporarily applying full control voltage across the UVR solenoid to reset it.

Abstract: A low voltage protection circuit for an air conditioner compressor which employs a series of diodes to control the application of an a.c. source potential to the resistive heater element of a conventional thermally responsive switch. The diode circuit maintains the heater element directly across the source potential at all times when the thermally responsive switch is open, but only during alternate half-cycles of the source potential when the thermally responsive switch is closed to thereby protect the compressor against potentially damaging low voltage conditions while reducing the power consumed by the heater element during periods of normal source voltage level.

Abstract: A crossed-field switch device is connected in parallel to a load device which may arc. The characteristics of the crossed-field switch device are that it will not conduct when a high voltage is applied, but when the load device arcs, the crossed-field switch device conducts, taking current from the arc so that the arc quenches. The crossed-field switch device thus is a crowbar which is automatically conductive when the applied voltage decreases due to a line or load short.

Abstract: The collector-emitter voltages (V.sub.ce) of each one of the two transistors of a single-pole-double-throw transistorized switch are independently sensed by a sensing circuit for producing a fault signal, whenever the V.sub.ce of each transistor concurrently approaches or exceeds the magnitudes of first and second DC reference voltages, respectively, by predetermined differentials. Control logic is responsive to the fault signal for removing the base drive from the conducting one of the transistors. An RC network is included in the sensing circuit, for delaying the production of the fault signal, both to avoid false triggering of the control logic, and to provide time for sequentially turning off one transistor and turning on the other transistor.

Abstract: An automatic current overload protection circuit for electrostatic precipitator power supplies of the type utilizing a ferroresonant transformer. A low voltage tertiary winding in association with the transformer provides an output voltage to a sensing circuit for inhibiting current flow into the primary of the transformer when the tertiary voltage falls below a predetermined threshold. Another output voltage developed in association with the high voltage secondary winding of the transformer is also utilized to independently inhibit current flow into the primary of the transformer when the secondary voltage falls below a predetermined threshold. A time delay may be provided to permit operation of the overload protection circuit only in the event of a sustained overload current condition.

Abstract: An electrical device is connected to the magnetic starter of an electrical motor to protect the motor windings from a loss of power on one or more input lines of a three phase power source. The device includes two transformers each being connected across two input lines and having one input line in common with each other. The transformer secondaries are each connected in a relay circuit so that a voltage on the secondary of each transformer above a predetermined value will actuate the relay in its respective circuit. The contacts of both relays are connected in series with each other and with the magnetic starter of the electrical motor so as to actuate the magnetic starter when both relays are closed. When the voltage on any of the three input lines drops substantially below a normal operating level, one or both of these relays will open, immediately turning off the magnetic starter and shutting down the motor to prevent damage to the motor windings.

Abstract: An electronic circuit for inhibiting overconduction of power transistors utilized in a switching mode and driven by a square wave signal of selected frequency. A reference voltage is utilized to compare the conduction of the transistors. The signal produced as a result of the comparison is utilized to control the base drive to that transistor through a logic circuit. Timing means is provided to delay the turn on or tuen off of the drive signal responsive to the comparison signal.

Abstract: A battery backup system provides DC power to a data processing system in the event of an AC power failure. A preferred embodiment supplies DC power from a plurality of series-connected batteries at a voltage level sufficient to operate a data processor. After a time delay, the batteries are connected in parallel to provide DC power at a lower voltage level sufficient to maintain information stored in a memory.

Abstract: Control circuit system wherein low level signals are delivered through small (miniature) gauge control conductors to remote control circuit breakers to control connection of load devices to load bus through use of solid state circuitry. Such control may be used between the flight station of an aircraft and the various load centers remote therefrom, in an automobile or in an industrial or utility system. The circuitry is also responsive to faults in the load circuits, and current limiting warning lights (CLWL's) located in the power supply of the control conductors may limit current and indicate the status of faults in the control and/or remote power circuits. A large number of CLWL's for the different circuits may be arranged in a matrix at a control station and means with corresponding load identifying indicia are provided to facilitate changes and correlation of lighted CLWL's with respect to the controlled load switching device.

Abstract: A device for cutting out non-essential loads in a generator and battery-fed electric plant includes a voltage detecting unit connected across the terminals of the battery. The detecting unit may be a relay. Whenever the voltage at the terminals falls below a predetermined level, the detecting unit effects the disconnection of the non-essential load or loads from the terminals of the battery and generator, while allowing the essential load or loads. The detecting unit preferably includes a differential amplifier having one of its inputs connected to a voltage divider connected in parallel with the battery and its second input coupled to a source of reference potential.

Abstract: A thermoelectric generator is equipped with a protective device which upon overload conditions disconnects a primary load, such as a rechargeable battery, in order to protect the secondary load, i.e., the burner, fuel pump and other ancillary items necessary to operate the thermoelectric generator. The protective device includes a voltage selectable breakdown diode, a transistor switch, a relay whose coil is connected to the transistor switch and preferably an anti-clatter circuit.

Abstract: A protective circuit for protecting a main d.c. circuit of the kind comprising a d.c. power source, a d.c. load, a contactor and a chopper. In the protective circuit, a resistor is connected in parallel with the series-connected contactor and load to permit continuous application of power supply voltage across the chopper. A circuit is connected to the connection point of the load and chopper to provide a signal synchronous with on-off of the chopper, and the output signal of this circuit and a signal corresponding to a chopper-on signal are applied to a logic circuit which provides the logical sum of these inputs for the detection of commutation failure of the chopper. The output of the logic circuit turns on a thyristor for deenergizing the contactor thereby disconnecting the load from the power source.

Abstract: Control apparatus is provided for a contactor which has a coil and at least one pair of contacts movable from an open position to a closed position in response to energizing the coil. The control apparatus includes apparatus for temporarily and permanently energizing the coil and switching apparatus for controllably energizing the coil.

Abstract: A circuit for protecting electrical apparatus from undervoltage of a source voltage by providing disconnection of the apparatus from the same. The circuit includes a relay controlled by a transistorized portion of the circuit responsive to conduction of a gas-discharge tube having specific breakdown and extinguishing voltage characteristics. The tube senses a voltage of that portion of the circuit having selectively adjustable A.C. and D.C. components proportionate to the source voltage, wherein a plurality of source voltage differentials can be selectively chosen at which connection and disconnection of the apparatus will be effected. The relay is also coupled to a capacitor to provide a time delay to prevent relay operation upon momentary voltage fluctuations.

Abstract: A memory circuit with protection circuit having particular application to MOS-IC memories is disclosed. The protection circuit prevents the memory from being damaged by an undesirable turn-on or turn-off sequence of main and substrate voltage supplies or by an abnormal substrate voltage.

Abstract: A power supply interruption detecting circuit which prevents an error in a write signal or sending and receiving signals of a data processing unit in the case of interruption of a commercial power supply or a power supply voltage drop resulting from an accident of other units connected to the same power supply. An abrupt drop of the power supply input voltage is detected by comparing the voltage of a CR circuit of a small time constant with the voltage of a CR circuit of a relatively large time constant. A slow input voltage drop is detected by comparing the voltage of the CR circuit of small time constant with a constant reference voltage. The power supply interruption is rapidly detected in substantially a constant short time regardless of input voltage variations and the write signal or the sending and receiving signals are each clamped at predetermined logic voltage, by which sending and writing of an error signal can be effectively prevented.

Abstract: A voltage-sensing solid-state electronic device for protection against the danger of fire originating in electric circuits, wiring and apparatus caused by defects or malfunction in said wiring or apparatus. Especially applicable for installation and use in aircraft.

Abstract: A combination electrical plug and cord and power cut-off unit with a male electrical plug rigidly secured to a housing from which the cord extends, the housing serving as a hard grip for insertion and removal of the plug, the housing containing an electrical relay holding circuit including an externally accessible momentary contact switch wherein a power failure in the supply line will effect a disconnect of the relay requiring a manual actuation of the switch to restore power to the cord leading to a machine or other electrical accessory.

Abstract: A solid state starter for a chiller compressor motor mounts directly on the compressor motor and comprises a bank of SCR's which are controllably switched to conduct current to the motor for starting and running. Electronic control modules are provided including a trigger module for triggering the SCR's, a current module (including current overload protection) for controlling the trigger module so that motor current is controllably delivered to the motor, and a voltage safety module for protecting against electrical faults. The SCR's are cooled by liquid refrigerant.

Abstract: In a phase monitoring arrangement for a three phase network which supplies a controlled d.c. motor through a controlled converter, a power line dependent discriminator along with R-C circuits forms a smoothed, rectified monitoring voltage which depends on the phase sequence and is sensitive thereto and to phase failure along with a supplementary monitoring voltage dependent only on phase failure, the rectified monitoring voltage and supplementary monitoring voltage being supplied to an evaluating circuit comprising differential comparing amplifiers at which the monitoring voltages are compared with constant reference voltages independent of faults and the output thereof used to control switching means and a current regulator so that in the event of incorrect phase sequence or of a phase failure, the switching means feed a blocking signal which suppresses firing pulses to the controlled converter and the current regulator feeds a control signal to control the converter to its operating limit.

Abstract: In a circuit breaker undervoltage release device, a spring powered trip slide is held in a latched position by a latch lever while the plunger of a solenoid is magnetically held in a seated position against the bias of a calibrated return spring. In the event of an undervoltage condition, the spring retracts the plunger, causing the latch lever to release the trip slide, which then moves to trip the breaker. Opening movement of the breaker mechanism first actuates a reset lever to load a reset spring and then returns the slide to its latched position. As the latch lever regains latching control of the slide, the reset spring discharges to snap the plunger to its seated position.