Abstract: A protection circuit which may be used, for example, in an audio amplifier to protect the output drive transistor against conditions of excessive power dissipation. The circuit includes apparatus for monitoring the product of output current and output voltage across the protected transistor and applying a feedback signal to reduce the power dissipation if a predetermined limit is exceeded. Specifically, a representation of the product of the output voltage and output current is obtained by providing a current proportional to each and passing such current through a respective semiconductor junction to produce a logarithmically related voltage. The logarithm of the power product is obtained by summing the logarithmic voltages developed across each respective semiconductor junction.

Abstract: In an impedance-measuring device for impedance protection, the phase positions of a plurality of alternating-current quantities are compared with the aid of a phase comparator. From the output signal thereof it is clear whether the impedance in a fault loop with a voltage U and a current I lies inside or outside an impedance zone, which is defined by means of a model impedance, Z.sub.k =R+jX. The comparator is supplied with input quantities corresponding to IX, U.sub.k, I and preferably also U.sub.p, where U.sub.k =U-IZ.sub.k, whereas U.sub.p relates to a voltage which is phase-shifted -90.degree. with respect to U. Quantities corresponding to IX, U.sub.p and I are each supplied to one input of a second logic component. This second logic component also has an input which is connected, via a delay element, to the output of a first logic component, the two inputs of which are supplied with quantities corresponding to I and U.sub.k, respectively.

Abstract: A high voltage generator of a television display is responsive to an alternating voltage, such as a retrace pulse voltage, for developing an ultor voltage at an ultor terminal. A protection circuit for the high voltage generator includes a comparator that develops a television display disabling signal when activated. A circuit that develops a sense voltage representative of the ultor voltage is coupled to an input terminal of the comparator so as to develop the disabling signal when the ultor voltage exceeds a predetermined level. To provide an overload disabling capability, an ultor beam current sensing circuit is coupled to the input terminal of an operational amplifier. The output terminal of the amplifier is coupled to a bias voltage source and to an input terminal of the comparator.

Abstract: The invention relates to a memory circuit in a relay protection device with a phase-locked loop, a monitoring circuit and an updating circuit. When a fault detector, a phase-change detector and/or an amplitude-change detector monitoring an a.c. network to which the protection device is connected supply an output signal indicative of a fault in the network, no updating of a storing member in the loop takes place.

Abstract: A protection circuit for an output transistor includes a transistor having two discrete emitter regions and which is responsive to both the voltage across the protected transistor and its drive current to provide both short circuit and overcurrent protection for the output transistor.

Abstract: A load indicator for A.C. motors has an analog multiplying circuit for producing a signal proportional to the product of the current of the A.C. motor and the voltage thereof. From this signal a signal is substracted which is proportional to the absolute value of the motor current. The average value of the differential signal is a measure of the load of the motor which is substantially independent of variations in the motor voltage, provided the proportionality constants are chosen in a suitable manner.

Abstract: A thermal protection circuit for the die of a transistor having a heat sink in which a signal proportional to the dissipative input current and a signal proportional to the dissipative applied voltage of the transistor are multiplied to produce a signal representative of the applied power to the transistor. This representative applied power signal is transformed into a simulated differential in temperature between the die of the transistor and its heat sink. Simultaneously, the temperature of the heat sink is determined and this temperature is added to the simulated differential in temperature between the die of the transistor and the heat sink to determine a sensed die temperature. A control responsive to this sensed die temperature reduces the applied power to the transistor.

Abstract: This invention relates to a loudspeaker protection device which disconnects the drive unit, or units, of the loudspeaker from an amplifier when the voltage across, or the current through, the drive unit, or one of the drive units, exceeds a predetermined level. The protection device includes a bistable device comprising a complementary pair of transistors arranged to be changed from the reset state to the set state when the voltage on an input terminal exceeds a predetermined level. The transistors are arranged to be both non-conductive when the device is in the reset state and both conductive when the device is in the set state. When the transistors are conductive, the collector current of one of them flows through the coil of an electromagnetic relay having normally closed contacts in the output circuit of the amplifier.

Abstract: Protective relay apparatus for electric power systems which logically relates the outputs of two algorithms to provide the fastest possible trip for the conditions of the post-fault voltage and current waveforms.

Abstract: An output from an OCL type power output circuit is applied to a loudspeaker load through a switching means such as a relay. A first detector circuit and a second detector circuit detect a first operating status (e.g., output d.c. level) and a second operating status (e.g., output current level of an output transistor) of the OCL type power output circuit, respectively. The detection output signals of the first detector circuit and the second detector circuit are respectively applied to a first detecting transistor and a second detecting transistor. In the normal operation status of the OCL type power output circuit, the first detecting transistor and the second detecting transistor are respectively biased into "on" states by the first detector circuit and the second detector circuit so as to permit predetermined currents to flow. When the first and second detecting transistors are in their "on" states they control a driving transistor into an "on" state.

Abstract: A system for electronically metering an A.C. electrical power system to derive performance parameters such as real and reactive power useful in revenue metering and fault protection applications. Voltage and current sensors associated with the power system provide isolated output signals proportional to the voltage and current in the system. From these signals finite-duration impulse-response filters periodically determine Walsh function correlation coefficients by integrating the voltage and current signals at least once during each period of the power system and periodically sampling and holding the integrated signal in sequence with the integration.

Abstract: A low pass filter is connected to a junction of a direct-coupled amplifier. The amplifier has a single-ended push-pull output stage consisting of two output transistors and series-connected two resistors. The output transistors are connected to a positive and negative d-c power sources, respectively. The series-connected two resistors are interposed between the two output transistors and defines an intermediate point therebetween at which substantially zero d-c voltage prevails when the amplifier is functioning normally. The junction of the amplifier, to which the low pass filter is connected, is between one of the output transistors and the series-connected resistors. The low pass filter is supplied with the voltage at the junction and applies its output to following isolating means. The means responds to the output of the low pass filter for isolating the intermediate point from a load device connected thereto.

Abstract: A rectifier unit for supplying power to a D.C. load including a transformer having a primary, a secondary and a saturable core, the secondary defining an output section and a control section. A ferroresonance control circuit simulates saturation of the transformer core and includes an electronic switch for controlling the degree of simulated core saturation and thereby regulating the rectifier unit output. Rectifier failure alarm circuitry produces a failure alarm in response to a number of rectifier unit malfunctions. The rectifier failure alarm circuitry is coupled to the ferroresonance control circuitry and comprises a rectifier alarm element operable between the first condition wherein a rectifier failure alarm is produced and a second condition. The failure alarm element is operated from its first condition when the electronic switch minimizes the rectifier system output.

Abstract: The method and the system are for detecting a current I and a voltage V of the electric power system and judging that there is fault if:.vertline.V-I.epsilon..sup.j.phi. .vertline.V.vertline./.vertline.I.vertline..vertline.<k.sub.ois fulfilled, where k.sub.o represents a constant and I.epsilon..sup.j.phi. an electrical quantity obtained by shifting the current I by a predetermined angle .phi.. In a modified form, the expression.vertline.V-I.epsilon..sup.j.phi. X.vertline.<k.sub.ois used, where X equals to .vertline.V.vertline./.vertline.I.vertline. or Z (a predetermined line impedance) whichever is smaller.

Abstract: A high power D.C. supply regulated for constant output power to be dissipated in varying loads such as encountered in cathode sputtering systems. A.C. input power is rectified to produce the desired D.C. The output D.C. voltage and load current are measured and a voltage signal proportional to their product is compared with a D.C. input control signal. The comparator "error" output signal controls a pass element that varies a D.C. current through saturable reactors in the A.C. input power lines to regulate the D.C. power into the load. The supply includes a limiting feature that is adjustable to a desired threshold level for limiting D.C. output power, voltage, and/or current so that the limiter will take control from the comparator to hold the supply output at a safe level.

Abstract: In an overcurrent protecting apparatus for interrupting overcurrent in accordance with a coordination tripping curve characteristic, there are provided a microcomputer, a current/voltage converter for converting an overcurrent into a first voltage, D/A converting means for converting each output successively delivered from the microcomputer into a second voltage, and comparator means for comparing the first voltage with the second voltage. The delivering of the outputs from the microcomputer to the D/A converting means continues until an output is delivered from the comparator means to a first input of the microcomputer. Another comparator is also provided for delivering its output to a second input of the microcomputer when the first voltage is extremely high.

Abstract: A circuit employing parallel power transistors intended to share the load current, includes a separate current sensing resistor for each transistor and independently operating protection circuits controlled by the voltage drop across the associated sensing resistor to limit the current in each power transistor to a safe level. The protection circuits each include zener diodes and resistors connected to vary the current limit in accordance with the voltage across the power transistors.

Abstract: An electrical power fault protection relay operates when the calculated impedance of the section of the system it protects shows a sudden change. The instantaneous voltage and current is measured. A calculation device then calculates the Fourier transform of a window of the actual voltage and current over a time interval and of the modified current that would flow if the voltage on each side of the time interval was zero. The actual impedance is calculated from the ratio of the Fourier transforms of the actual voltage and the modified current.

Abstract: A first resistor and a second resistor are connected in series across the collector and emitter of a transistor that is to be protected thereby to detect a voltage across the collector and emitter thereof, as well as to detect a collector current or an emitter current thereof, and a third resistor is connected to be collector or the emitter of the transistor that is to be protected. A detector transistor is driven by a voltage produced across the second and third transistors. A fourth resistor is connected between the collector and the base of the detector transistor, one end of the fourth resistor connected to the base of the detector transistor being connected to a constant-current circuit, and the other end of the fourth resistor connected to the collector of the detector transistor being connected to the base of a control transistor. The emitter of the control transistor is connected to the collector or the emitter of the transistor that is to be protected via the third resistor.

Abstract: Protective relay apparatus for developing signals responsive to subsynchronous current oscillations in a three-phase electrical power system, and for analyzing the signals to determine when corrective action is necessary. The positive sequence component of a subsynchronous current oscillation is developed via a summing arrangement, which eliminates the need for sequence filters. The positive sequence component of a subsynchronous current oscillation is processed to determine if it is an electrical transient which would shock the mechanical system of a turbine generator, or machine, to be protected, into mechanical resonance. It is also processed to determine if it is due to a growing mechanical oscillation of a turbine generator, such as might be initiated by a change in a parameter related to the turbine generator.

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: A direct current, high-speed circuit breaker which is connected in series at the direct current side of one of a plurality of inverters connected in parallel in a high voltage transmission system, and which is caused to open when the magnitude of the direct current to the one inverter exceeds a threshold value, is further controlled to open in response to the occurrence of a commutation failure only when such failure occurs simultaneously with reduction of the commutation voltage of the one inverter below a rated value by more than a first predetermined magnitude such that proper operation of the one inverter is no longer assured, and the threshold value of the direct current is increased from a normal value to a selected higher value in response to a reduction of the commutation voltage below the rated value by more than a second predetermined magnitude which is less than the first predetermined magnitude.

Abstract: A method of, and apparatus for, monitoring the run-up to speed of asynchronous motors which are turned-off within a permissible blocking or cutoff time of the motor when the speed run-up is improper, wherein after turning-on the motor there is determined a first value of an electrical magnitude which is dependent upon the phase angle between the motor current and the motor voltage after expiration of a first time-delay following turning-on of the motor, and there is then determined a second value of said electrical magnitude after expiration of a second time-delay following the turning-on of the motor. Both the first and second values are compared with one another, and the motor is turned-off when, following such comparison, there is present a magnitude indicative of improper run-up to speed of the motor.

Abstract: In a glow-discharge workpiece-treating system's control system, the existence of a direct short-circuit between workpiece and glow-discharge treatment chamber is ascertained. This is done by comparing a voltage-indicating signal and a current-indicating signal against respective threshold levels, and generating a short-circuit signal when the voltage-indicating signal falls below its threshold level and the current-indicating signal exceeds its threshold level. Preferably, the threshold level for the voltage-indicating signal, although lower than the arc-discharge voltage of the system, is higher than the glow-discharge voltage of the system.

Abstract: A resistor, a DC source and a current converter are connected in series between one terminal of the field winding and the ground. When a ground fault occurs on the field winding, it is detected by the output of a voltage detector connected across the resistor or the output of the current converter, and an alarm device is operated. At the same time, another resistor is connected between the other terminal of the field winding and the current converter through a switch, and the magnitude of the ground fault is calculated by the outputs of the voltage detector and of the current converter before and after closure of the switch. When the magnitude of the ground fault is large the generator is disconnected.

Abstract: A dynamo-electric machine is provided with a protective circuit arrangement whereby the machine is caused to be switched off if a short circuit current flowing in the machine exceeds a predetermined level.False operation of the protective circuit is avoided by incorporating a discriminating circuit which is able to distinguish the phase angle between the current and the voltage. This causes the protective circuit to trip for an over load current where the phase angle difference is small and the power factor near unity, which occurs with resistive fault situations; and not to trip where the phase angle difference is high, and thus there is a low power factor indicating a reactive condition, which occurs on start-up of the machine. A machine is able to run more safely as a result.

Abstract: A protective relaying system including a protected AC transmission line and detection means for detecting a change in propagation mode of a traveling wave propagating along the transmission line. The transmission line has a pair of line ends and a surge propagation time .tau., and the detection means is effective for comparing a value of the traveling wave as it passes one of the line ends at a time t-.tau. and a value of the traveling wave as it passes the other of the line ends at a time t after the surge propagation time has elapsed for detecting a change in wave value resulting from a change in wave propagation mode.

Abstract: An energy limiting foldback circuit for use with power supply having a power control device in its output. The energy limiting foldback circuit contains a voltage sensing device for sensing the potential drop between the input and the output of the power control device. The foldback circuit also includes a current sensing device for sensing the current through the power control device. A conduction control circuit is included which is responsive to the outputs of the voltage sensing device and the current sensing device. The conduction control circuit acts to control the operating conduction through the power control device. The energy limiting circuit can also include a pulsing circuit operative in the event of output fault to periodically pulse the power control device into a momentary conduction state.

Abstract: An arrangement for supervising an electrical line for short circuits in which current and voltage signals are derived from the line current and line voltage at a predetermined measuring point. The current and voltage signals are relatively weighted by multiplying at least one of these signals by a weighting factor which is at least approximately free of phase rotation. At least one auxiliary signal is formed corresponding to the sum or difference in each case of a pair of relatively weighted current and voltage signals. An amplitude comparison is carried out between the auxiliary signal and a reference signal. The weighting factor is related to the current signal and the voltage signal, and is a quantity at least approximately corresponding to the characteristic line resistance or its reciprocal value.

Abstract: A commutation sensor circuit for a DC-to-DC silicon controlled rectifier (SCR) chopper circuit to protect against commutation failure by determining the commutation capability of the chopper. This determination is made by testing two conditions, first, the applied voltage is measured and used to predict the commutation voltage available after a main SCR has been gated on and a commutating capacitor charged, and second, the available commutation voltage is measured after the main SCR has been gated on and the commutating capacitor charged. The first test allows the chopper to turn on if the predicted voltage when compared to the current flowing is sufficient to commutate the chopper. The second test initiates a commutation if the current flowing in the chopper reaches the maximum commutating ability of the chopper.

Abstract: A trolley wire for conveying direct current power to an electrically powered vehicle in an underground mine is connected in series with a shunt to a power source. The current drawn by the trolley wire passes through a circuit breaker and the shunt. The shunt generates a voltage input signal proportional to the current drawn by the trolley wire. A solid state comparator device receives the input signal and compares it to a reference signal having a magnitude representing the maximum level of current permitted to flow through the conductor. If the reference signal exceeds the input signal, the comparator device supplies an output signal that oscillates between a positive and a negative voltage to a trip circuit. The output signal actuates the operating coil of the circuit breaker so that the circuit breaker contacts remain closed to permit current to flow through the shunt to the trolley wire.

Abstract: Apparatus for detecting the presence of subsynchronous current components in an electrical generating or transmission system is disclosed. Input signals, representative respectively of line voltage and current, are conditioned and initially filtered to suppress high frequency noise. The input voltage signal is further limited and filtered to produce a constant amplitude, sinusoid reference. The input signals are then multiplied to yield the subsynchronous current signal components, if any, which undergo further filtration by a bandpass filter circuit. In addition, the detection apparatus is provided with circuit means for insuring protection against overvoltage and current surge conditions.

Abstract: Apparatus for protecting a power system or a portion thereof against the effects of subsynchronous current oscillations is disclosed. A signal representative of or proportional to the subsynchronous current is developed via synchronous modulation and bandpass filter techniques. This signal is fully rectified to produce a waveform from which information can be garnered from both the positive and negative half-cycles.A peak holding and peak status circuit then compares successive peaks of the rectified signal, which circuit is adapted to recognize only those peaks having increasing amplitude. The output of the peak holding and peak status circuit is utilized by three comparator circuits which individually employ differing reference voltage levels for overall evaluation purposes.

Abstract: In a protective arrangement for protecting a brushless synchronous machine against overvoltage at a field winding which is connected to a rotating excitation rectifier which is fed from an exciter machine, in which the field winding is short circuited by means of a solid state switching element when overvoltages occur, a voltage comparison means is provided to which are fed as respective first and second inputs, a first input voltage proportional to the primary voltage of the exciter machine and a second input voltage proportional to the primary current of the exciter machine with the proportionality constant chosen such that for normal operation of the synchronous machine the absolute value of the second input voltage is lower than the first input voltage and for operation when the field winding is short circuited, the absolute value of the second input voltage is greater than the first input voltage.

Abstract: This protective relay circuit responds to interphase faults on a three-phase power line by causing a circuit breaker connected in the power line to be tripped three-pole in response to interphase faults, but does not respond to a single line to ground fault, allowing a single pole to be tripped for this latter type of fault.

Abstract: An out-of-step relay for an alternating potential electric power transmission line is disclosed wherein the decision to trip is determined by the rate of change of the phase relationship of the voltages at the remote and local ends of the transmission line as well as by the magnitude of the phase difference of the remote and local voltages. More particularly, there is described a pair of AND networks which provide two timing signals proportional to the phase difference of the voltages and a pair of timing devices; one of said devices timing the difference in the time of the two timing signals to establish the rate of change of the phase relationship and the other of said devices timing the sum of the two timing signals to establish a signal which is representative of the magnitude of the phase relationship.

Abstract: A protective device limiting the current flow through a power transistor 11 in a final stage of an integrated circuit comprises, as part of that circuit, a normally nonconductive shunt transistor 31 which is turned on by a monitoring transistor 22 whenever the collector current I and the collector-emitter voltage V.sub.CE of the power transistor reach values beyond a protective curve 52 plotted on a current/voltage diagram. The base-emitter circuit of the monitoring transistor 22 is connected across an output resistor R.sub.2, in series with the power transistor 11, via a diode 21 of logarithmic conduction characteristic, that diode being also connected across the power transistor in series with a voltage-sensing network. This network includes a voltage divider R.sub.3, R.sub.5 in series with a Zener diode 33, the voltage divider being connected in parallel with a switching transistor 35 whose base is tied to a tap of the divider.

Abstract: A protection device for a thyristor inverter circuit of an induction heating cooking oven wherein commutation failure of a thyristor is detected by determining that the conduction period of the thyristor is outside a predetermined period or that a voltage applied to the thyristor is outside of a predetermined magnitude. The protection device deactuates the inverter to prevent breakdown of the thyristor and reduces the number of operations of the circuit breaker which is a final protection device. Additionally provided are linked switch actuator apparatus for placing a switch for actuating a thyristor control circuit in a state in which it is always actuated in advance of the actuation of a switch for a heating coil in order to prevent occurrance of a transient high voltage due to the switching of an inductive load in the inverter circuit, and an overheating protection circuit for detecting an abnormal temperature rise of the heating coil and an abnormal load condition to deactuate the inverter.

Abstract: A protective relay arrangement for an A.C. power system wherein the occurrence of a fault is detected by monitoring the phase or amplitude relation between at least one pair of signals which, when a fault occurs in the system, are functions of a current and/or voltage which would have occurred in the power system if the or each emf source in the system had a value equal to the pre-fault voltage at the point in the system where the fault has occurred.

Abstract: A protective relay circuit. An electrical system signal quantity is monitored and applied to a filter and to a bipolar threshold device in parallel with the filter. The bipolar threshold device has a zero output signal level as long as the magnitude of the monitored signal is less than some predetermined value. When the monitored signal exceeds the predetermined value, the output of the bipolar threshold device will be substantially equal to the monitored signal level minus the predetermined value. The output of the filter and the output of the bipolar threshold device are combined in a summing amplifier to provide a signal for controlling the trip coil of a circuit breaker. When the circuit is used in an overcurrent or overvoltage protective relay, the combined signal is rectified and applied to a level detector which provides the signal for controlling the trip coil of the circuit breaker.

Abstract: In capacitor equipment which includes a series-connection, connected to an alternating voltage network, of two anti-parallel connected thyristors, one capacitor and one reactor, a control device is connected to the control electrode of the thyristors and arranged to ignite the thyristors alternately at times in the vicinity of the peak value of the alternating voltage. A sensing member is provided for sensing an operating magnitude in the series connection and a level-sensing member is connected to the sensing member and to the control device. The level-sensing member influences the control device to produce ignition of both thyristors of the instantaneous value of the operating magnitude falls outside a pre-determined interval.