Abstract: A system of protection for an electric power generating system having a poly-phase generator switchably coupled through a generator control breaker to a load distribution bus, wherein the generator output voltage is controlled by a generator control unit which utilizes isolated voltage and current sense signals having a magnitude proportional to the output voltage and current for each phase of the poly-phase generator, the isolated voltage and current sense signals being generated by isolated voltage and current sensors, comprises a first circuit for monitoring the magnitude of each of the isolated voltage sense signals and generating a first output control signal if the magnitude of any isolated voltage sense signal is below a first predetermined threshold.

Abstract: A method and a device, after a fault has occurred in a power network, for measuring and recreating the phase currents I.sub.B prior to the occurrence of the fault by determining continuously, starting from sampled measured values of the phase currents up to the time of the fault for each phase, the amplitude I and the phase angle .phi. of the phase currents based on two consecutive sampled measured values, whereupon a comparison is made between the last determined value I.sub.k obtained and the rated current I.sub.n of the power network. If I.sub.k is greater than I.sub.n, it is considered that a fault has occurred and the phase currents prior to the fault are indicated as I.sub.B =I.sub.k-1 .multidot.sin (.phi..sub.k-1 +.omega.(t-t.sub.k-1)).

Abstract: A circuit is provided for detecting a short circuit in a remote low-side driven load wherein a single conductor is used to both transmit a control signal from a microprocessor controller through a local driver to the remote driver of the load and also to transmit fault signals from the remotely driven load back to the control means. A control signal is transmitted from the microprocessor controller through a local driver circuit to a remote driver circuit on a single conductor. A short circuit at the remote load causes a fault signal to be latched for later detection by the microprocessor and a short circuit at the local driver is immediately detected.

Abstract: An overcurrent protection circuit for a power transistor for generating a main current in response to a gate drive voltage generated by a gate circuit. The overcurrent protection circuit includes a current detection circuit for detecting the main current flowing in the power transistor to generate a detection voltage corresponding to the main current, and a level detection circuit connected to receive the detection voltage for generating a control current corresponding to a difference between the detection voltage and a prescribed value when the detection voltage exceeds the prescribed value. The overcurrent protection circuit further includes a current control circuit connected to receive the control current for limiting the main current by regulating the gate drive voltage based on the control current, and a drive instruction control circuit connected to receive the control current for making the main current zero by controlling the gate drive voltage to an OFF condition based on the control current.

Abstract: The relay includes an input module capable of receiving 70 volt and 5 amp signals, respectively, from conventional instrument transformers, which are responsive to power line signals at their primaries. Output signals from the input module have specified, standardized levels suitable for electronic processing circuits, i.e. 1.4 volts and 0.1 volt. The output signals from the input module are applied through an accessible connector to a separate processing module which uses those signals in a conventional manner to determine possible faults on the power line. Low-level testing is accomplished by testing the outputs of the input module and by applying test signals simulating the standardized outputs of the input module to the processing module.

Abstract: A device for measuring energy delivered by a motor to a load is adapted to be connected to the motor which is coupled to the load and connected to a power source through first and second power supply lines. The device includes a line voltage sensing circuit for sensing the voltage across the power supply lines, a line current sensing circuit for sensing the current flowing through the motor and a pulse width modulator which modulates the sensed voltage to produce a pulse width modulated first electrical signal. The device also includes a first switch, responsive to the pulse width modulated first electrical signal which modulates an output of the line current sensing circuit to produce a power waveform and an integrator which integrates the power waveform to produce an output signal indicative of the energy delivered by the motor to the load.

Abstract: A sub-cycle digital distance relay which uses only the first N/2 samples after a fault to calculate the distance to the fault using a Full Cycle Fourier Algorithm which operates on N samples, where N is the number of samples taken in a cycle of the power signal. The DC offset in the first N/2 samples taken after detection of the fault is cancelled using the N/2+1 sample taken after detection of the fault. The resulting DC adjusted N/2 samples are then multiplied by -1 in order to take advantage of the symmetry of the sine wave of the power signal in estimating the remaining N/2 samples of the first cycle of the power signal after detection of the fault. By so calculating N/2 artificial samples from the first N/2 actual samples taken after the fault, the digital distance relay of the invention can estimate the distance to the fault and thus provide a reliable trip signal in less than one cycle of the power signal.

Abstract: In an electric circuit supplying AC line current rent to a load (30, 31) from an AC source (26) of given frequency providing repetitive cycles, arc detection is provided by sensing cycle to cycle changes in the AC line current. The AC line current is sampled with a harmonic notch filter (72) at a plurality of n phases .THETA..sub.1 through .THETA..sub.n during each of a plurality of m cycles of the AC source (26), to provide a plurality of currents I.sub.n,m, where n is the phase and m is the cycle. The differences (I.sub.n,m)-(I.sub.n,m-x), where x is a designated number of cycles, provide a plurality of current difference signals. The absolute values of these current difference signals ID are accumulated in a synchronous summer (94) over the m cycles. An arc indicative signal is generated in response to given conditions and given combinations of conditions (116) of the cumulative absolute current difference signals ID.

Abstract: A method and apparatus provides for a measurement technique which approximates the true rms value of a current waveform. The technique involves converting the current waveform to a voltage by rectification and determining the peak value and the average value of the resultant voltage. A summing circuit combines the two values at a predetermined ratio to create a DC voltage that is approximately equal to the rms value of the input currents. The DC voltage output is suitable for a wide range of applications. A combination of the approximation circuit with a time integrating circuit and a level detecting circuit produces a low cost solid state overload relay in a preferred embodiment of the invention. Other uses include metering and use as a current feedback control signal for controlling PWM inverters and the like.

Abstract: A high-power power supply produces a controllable, constant high voltage output under varying and arcing loads. The power supply includes a voltage regulator, an inductor, an inverter for producing a high frequency square wave current of alternating polarity, an improved inverter voltage clamping circuit, a step up transformer, an output rectifier for producing a dc voltage at the output of each module, and a current sensor for sensing output current. The power supply also provides dynamic response to varying loads by controlling the voltage regulator duty cycle and circuitry is provided for sensing incipient arc currents at the output of the power supply to simultaneously decouple the power supply circuitry from the arcing load. The power supply includes a plurality of discrete switching type dc--dc converter modules.

Abstract: A method and a device for phase selection for single-pole tripping of high-impedance ground faults in direct grounded power networks. Starting from the ratio of the negative-sequence voltage to the zero-sequence current (U2/I0) and the ratio of the negative-sequence voltage to the positive-sequence voltage (U2/U1), two criteria with different conditions are formed, each of which indicating a faulted phase, and if both criteria indicate the same phase as faulted, single-pole tripping can take place.

Abstract: A method for measuring capacitance in a power conversion system by measuring the time rate of discharge of the capacitance means and computing the value of capacitance corresponding to the measured discharge rate and a method for verifying that a filter in the power conversion system is effective for suppressing preselected frequencies corresponding to signalling frequencies used in a transit system. In this latter form, the system periodically initiates a self-test function in which the preselected frequency is injected into the system for verifying that the system will detect signals at the preselected frequency.

Abstract: A circuit breaker for protecting a motor-driven system from overcurrents and undervoltages includes both current and voltage sensors and derives a precise estimate of electromagnetic torque output from sensed currents and voltages. A contactor similarly includes torque estimating capability.

Abstract: A low voltage electric power monitoring and circuit breaker system includes two processors. The first processor activates the circuit breaker when an overcurrent condition is detected and the second processor monitors the current sensed by the first processor and logs overcurrent values which arm the breaker as well as overcurrent values existing at the time the breaker is tripped.

Abstract: An arrangement for ensuring that a proper control level for a controlled unit is maintained when a supply voltage is removed from a control unit of a control system includes a switching circuit coupled between the control unit and the controlled unit. The controlled unit couples the control signal generated by the control unit to the controlled unit when the supply voltage is present and is responsive to the absence of the supply voltage for decoupling the output of the controlling unit from the input of the controlled unit. In this manner, a current path established by a protection circuit within the control unit when the supply voltage is removed is decoupled from the controlled unit and does not adversely affect the operation of the controlled unit.

Abstract: An apparatus for protecting an electrical power system supplying electrical power to an electrical load comprises a transformer for sensing an operating condition of the electrical power system and for producing an analog signal representative of the operating condition, and a microcomputer for periodically sampling the analog signal and for converting the analog signal into a series of digital signals. The microcomputer includes circuitry for deriving a digital value representative of a square root of the series of digital signals and circuitry for processing the digital value over time to determine a processed value which is a function of both the sensed operating condition and time. A circuit breaker is responsive to the microcomputer for disconnecting the power system from the load in the event that the processed value is not within preset limits.

Abstract: Method and apparatus are provided responsive to the circuit parameters at one or more locations of an electrical power transmission and/or distribution network for detecting protective device operation. The detection of the protective device operation is utilized to locate faults and also to ascertain the status of protective devices. This information is useful in automated power systems for desirable isolation and sectionalizing of faults for optimum restoration of the network. A fault detection unit of the present invention is responsive to sensed circuit parameters and provides at least first and second outputs indicative of protective device operations that open the circuit. The first output is provided upon the occurrence of an overcurrent followed by the loss of a circuit parameter, such as voltage, for a specified time duration. In a preferred arrangement, the timing for a specified time duration is started when the overcurrent ends.

Abstract: A lighting circuit for a vehicular discharge lamp having a DC voltage booster circuit for boosting an input voltage from a DC voltage input terminal, comprises a current detector, a voltage detector, an abnormality judging circuit, and a power cutoff relay circuit. The current detector acquires a detection signal concerning an output current of the DC voltage booster circuit. The voltage detector acquires a detection signal concerning an output voltage of the DC voltage booster circuit. The abnormality judging circuit compares the levels of the detection signals from the current detector and the voltage detector with each other to determine whether or not the lighting circuit is in an abnormal status. The power cutoff circuit inhibits power supply to the discharge lamp upon reception of a signal from the abnormality judging circuit representing an abnormality in the lighting circuit.

Abstract: A digital protective relay apparatus for protecting a power system comprises an accident determination section for determining an accident in the power system, which receives a voltage and a current of the power system from the power system to determine an accident in the power system using the voltage and the current, outputs a determination signal indicating the presence/absence of an accident in accordance with a result of the accident determination, and outputs a first trip signal upon detecting an accident in the power system in accordance with the accident determination, a protection sequence section for receiving the determination signal from the accident determination section to determine necessity of a trip output by performing predetermined sequence processing using the determination signal, and outputting a second trip signal upon obtaining a determination result indicating that a trip command is to be output, and a trip generator for generating, when both of the first and second trip signals are o

Abstract: The problem of noise and undesirable oscillations on a DC bus (46) are minimized using a transient suppressor (50) in connection with a 270 volt DC power system (10). The power system (10) includes an excited generator (17) developing AC power rectified to power the DC bus (46) for connection to loads (36). The transient suppressor (50) comprises a resistor (52) and a switch (54) connecting the resistor (52) across the DC bus (46). A control (60) senses bus voltage and load current and controls the switch (54) in response thereto. Indeed, the switch (54) is controlled in one of two modes of operation. The first mode comprises voltage control in which the switch (54) is turned on with a single pulse to reduce over voltage conditions, without introducing EMI noise. The second mode comprises pulse width modulating the switch (54) under low current conditions to reduce low frequency oscillations on the DC bus (46).

Abstract: A circuit breaker bandwidth limits a sensed rate of change of current, di/dt, in the neutral conductor of a protected electrical system and fullwave rectifies the bandwidth limited di/dt signal for comparison with an instantaneous trip reference signal. The bandwidth is selected to provide a selected relative sensitivity of the instantaneous trip to sinusoidal currents associated with overcurrent faults and step currents associated with sputtering arc faults. The rectified bandwidth limited di/dt signal is also filtered and delayed for comparison with a delayed trip reference signal. The time constant for the filter is selected to provide a selected relative sensitivity of the delayed trip to overcurrent faults and sputtering arc faults. A low mu sensing coil used to generate the di/dt signal can also serve as the neutral current sensing coil of a dormant oscillator ground fault protection system.

Abstract: Voltage/current characteristics control circuit particularly for protecting power transistors, which comprises at least one power transistor; the emitter terminal of a first transistor is directly connected to the output of the power transistor; the emitter terminal of a second transistor is connected to the first terminal of the power transistor by means of a first resistor. The collector terminal and the base terminal of the first transistor are connected to a current source. The base terminal of the first transistor is connected to the base terminal of the second transistor, and the circuit furthermore comprises a protection circuitry. The circuitry is connected to the collector terminal of the second transistor through a differential stage which comprises a third transistor and a fourth transistor; the third transistor and fourth transistor have a respective second resistor and third resistor arranged in series.

Abstract: An electronic automatic energizing damping device for connection to a source of electrical energy to protect and safeguard continuously all the devices, instruments, equipment and systems, connected to the source. The device comprises a control stage and a power stage. The control stage monitors the operating conditions of both the A.C. line and the load energized by it via the power stage, in order to detect irregularities in any of the programmed parameters of the voltage or the current, and supplies control signals that regulate the power stage. The power stage supplies the energy of the network to the load, according to the commands of the control stage. The control stage features a voltage sensor circuit, a current sensing circuit, a comparison circuit to receive the output of the voltage sensor circuit and an energy relay control circuit. The power stage comprises a surge breaker and suppressor, and an optical interface circuit.

Abstract: A circuit limits the output drive current from an interface drive circuit comprising drive transistors. The circuit makes dual use of an external series supply resistor as a current sensing element. The increased voltage drop across the external resistor due to excessive current draw through the drive transistors is coupled to a control transistor, which reduces base drive current to the drive transistors in response to the increased voltage drop.

Abstract: A solid state circuit interruption arrangement in a distributed power network provides fast and reliable circuit interruption. A common power source provides power to a plurality of loads via respective current paths. A main circuit breaker and a plurality of solid state circuit breakers are arranged to interrupt the current paths in response to command signals sent from a central controller. Current sensors and voltage sensors are coupled to the current paths for monitoring purposes. An automatic controller responds to any of the current sensors detecting a fault condition by automatically generating a command signal, which forces the associated solid state breaker to interrupt the associated current path. Thereafter, the controller automatically generates a signal to the main circuit breaker to interrupt the power provided from the common power source in the event that the associated current path is not interrupted by the solid state breaker.

Abstract: An overcurrent protection device is provided for one or more phases of a circuit that generates a control signal dependent upon an adjustable trip level setting after a fault has occurred. The device includes a blocking level detector that blocks the generation of the control signal is the current in any of the phases exceeds either a first predetermined blocking level or the adjustable trip level setting. In a preferred arrangement, before control-signal generation, the device also requires that the current in at least one phase is below a predetermined load level.

Abstract: A method and system of transformer protection in which parallel admittance currents indicative of the apparent excitation state of a transformer to be protected are evaluated from the transformer terminal voltages and currents sampled at a proper interval, and discrimination between an internal defect and excitation inrush is made in response to a magnitude of the parallel admittance current, and a breaker opening command is issued in response to a judgement of internal defect. The method and system enables high-accuracy and high-sensitivity fault detection through a simple computation.

Abstract: A connection control device for controlling the connection of a small generator unit, which is installed at the consumer's location, to an electric power system. The connection control device detects variations in frequency components which result from interruptions in the distribution of electric power to the consumer from the electric power system. When a significant variation in a frequency component is present, the connection control device disconnects the consumer from the electric power system in order to prevent injury to line workers.

Abstract: A semiconductor device drive circuit is provided for turning on and off a semiconductor device that comprises a main static induction transistor and a sense static induction transistor. The drive circuit comprisees a first current source having one terminal connected to a power supply and its other terminal connected to said main static induction transistor, a second current source having one terminal connected to the power supply and its other terminal connected to said sense static induction transistor, a third current source having terminal connected to the power supply and its other terminal connected to the first current source, and a fourth current source having one terminal connected to the power supply and its other terminal connected to the second current source.

Abstract: A distance relay for protection of power transmission lines, having a plurality of mho elements, each with a predetermined mho impedance characteristic. The relay has the capability of calculating a polarized reference voltage which remains constant through fluctuations in measured transmission line voltage. The difference voltage between the measured line voltage and the product of the measured line current and the mho element characteristic impedance is then compared against the polarized reference voltage in a product-type phase comparator to determine under-impedance conditions. If an under-impedance condition is present, the mho element produces a set output and a calculated "torque" value. The set outputs, if any, are then compared against a look-up table for fault type determination. If more than one set output is present, the magnitudes of the respective torque values are compared for fault type determination.

Abstract: An arcing fault detector is set up to identify arcing faults and to distinguish them from other disturbances in a circuit. A plurality of electrical conditions are monitored and the conditions are tested against predetermined parameters for establishing a series of logical conditions relating to the presence of an arcing fault. A logic circuit combines the logical conditions for deciding on the presence of an arcing fault. An output signal of the logic circuit is used to activate a relay for interrupting the supply of electrical power to the circuit.

Abstract: An inverse time delay circuit includes an integrator for receiving a signal representative of a voltage or current in an external circuit and a reference signal. The integrator produces a control signal representative of the integral of the difference between the signals. A comparator compares the control signal to a second reference signal to produce an output which changes logic states when the magnitude of the control signals exceeds the magnitude of the second reference signal. A circuit is provided to control the magnitudes of one or both of the reference signals thereby providing control of the instantaneous and/or ultimate trip levels of the circuit.

Abstract: In an electric power converter comprising at least one pair of serially-connected, alternately conducting controllable electric valves spanning a pair of d-c conductors, the conducting state of each valve is detected by comparing the actual magnitude of valve current with a predetermined low threshold level and by comparing the difference between the juncture potential of the two valves and a reference potential of one of the d-c conductors with the potential diffence between both d-c conductors. If both comparisons indicate the valve is in a conducting state and if this state is indicted concurrently for both valves, logic means is operative to indicate that a "shoot through" fault has occurred. In this abnormal event, whatever turn on and turn off signals for the two valves were extant at the time such operation of the logic means commenced will be prevented from changing while both valves are conducting.

Abstract: An apparatus capable of acting as a current-limited voltage source or a voltage-limited current source is disclosed. The output of the apparatus is provided by a differential amplifier. The current and voltage outputs are compared to positive and negative current and voltage limits. Depending on whether the apparatus is in the voltage mode or the current mode, the inverting input of the differential amplifier is clamped to the appropriate voltage or current comparison signal, respectively, to provide an error signal to the differential amplifier. This clamping is current limited so that if the output current limits are exceeded while in the voltage source mode, a clamp to one of the current comparison signals occurs and dominates the voltage clamp. Similarly, if the output voltage limits are exceeded while in the current source mode, a clamp to one of the voltage comparison signals occurs and dominates the current clamp.

Abstract: An apparatus for preventing damage to the output stage of a driver circuit for use in an overdrive/functional tester, while the output stage is providing logic high or logic low signals, is shown to include a first sensor for sensing the current in the output stage, a second sensor for sensing the voltage in the output stage, a multiplier for multiplying the sensed current with the sensed voltage to determine the power dissipated in the output stage, a filter to account for thermal/time characteristics in the determined power dissipated and a comparator for comparing the filtered power with a power reference value and for generating an indication signal reflective of such comparison.

Abstract: A method of locating a phase-to-ground fault in a radial distribution system with a tapped load. The method includes determining the positive-sequence impedance from the residual current, the residual current compensation factor and the phase-to-ground voltage of the faulted line. The positive-sequence impedance is then used to determine the distance to the fault.

Abstract: In a load controlling apparatus used in, for instance, an automobile, equipped with a mulfunction diagnostic circuit, there are employed:a power source V;a load 1 operated by power supplied from the power source V;a drive 3 for controlling supply of the power to the load 1;a control 4 for supplying a control signal "a" to the drive 3;a first and second detector 2, b for detecting the current flowing condition "b" to the load 1 based upon the control signal "a" derived from the control 4, and also the voltage condition "C" applied to the load 1;a judging device 11 to 18 for judging an extraordinary condition of the load 1 and the drive 3 based upon the signals from the first and second detector 2, b, and the control signal "a"; and,a display outputting a signal "d" representative of the respective extraordinary condition of the load 1 and the drive 3 based upon the judgement result obtained from the judging device 11 to 18.

Abstract: The output terminals (15, 16) of an analog sensor (14) are monitored by a microprocessor (17). The microprocessor is DC coupled to a main analog ground terminal (16) of the sensor, while also separately being connected to a main power ground terminal (13) at which ground reference potential is provided to the microprocessor. A resistor (38), a semiconductor switch (36) and a printed circuit board metalization trace (35) provide a normal low resistance connection between the main analog sensor ground terminals (20) and the main power ground terminal (13). Current sensing circuitry (33) limits the current passed through the low resistance connection and thereby prevents excessive current from damaging printed circuit board metalization paths (34, 35) connecting the sensor analog ground terminal (16) to the main power ground terminal (13).

Abstract: A load condition detecting a control system for supplying a load current to a load from a power source wherein, when said load exhibits a short circuit condition, a driving signal controlling the application of high current to the load is immediately pulled down, shutting-off the flow of high current to the load. Thus, even before a short circuit condition is detected by any logic means, the high current is disconnected from the load, preventing any possible damage to the load or other circuitry. The system also detects an open circuit load condition. Upon detection of either an open or a short circuit load condition, the system then blocks the driving signal from being applied to the driving circuitry until the system is reset.

Abstract: Semiconductor device protection circuit (10) provides increased power dissipation (current) limits for FET (11) when lower FET temperatures exist. The FET drain to source voltage (V.sub.DS) is monitored to provide a current sense signal (54). When the current sense signal exceeds a predetermined reference limit signal (V.sub.REF,55), a control circuit (23, 32) reduces current (power dissipation) in the FET. Circuitry (24) provides the reference limit signal (V.sub.REF) with a predetermined temperature variation as a function of the sensed temperature of the FET whereby for low device temperatures higher power dissipation (current) limits for the FET are provided. An additional control circuit (21, 30) provides short circuit overcurrent protection by reducing current in the FET when sensed FET current exceeds a predetermined limit. A delay circuit (39) inhibits operation of at least the control circuit (20, 32) until a predetermined time (t.sub.1) after the FET is turned on.

Abstract: The DIN Standard VDE 160/01.86 involves specific requirements as far as the dielectric strength of electronic devices is concerned which are intended for operation at high-voltage networks. A guard circuit for the protection of capacitive loads is described. In this system, a current detector means is provided to detect the current flowing into the load and to emit a first blocking signal at least when the amount of the detected current exceeds a preset maximum value. A voltage detector means is provided to detect the voltage in the supply network and to emit a second blocking signal when the amount of the detected voltage exceeds a preset maximum value. A controllable switching means is provided which is so designed and in such controlled communication with the current and voltage detector means that the load will be isolated from the supply network as soon as at least one of the two blocking signals is applied.

Abstract: A high voltage electrode device including a plurality of individual electrodes having end portions projecting beyond an insulating surface and arranged to form at least one group or electrically connected electrodes and apparatus for energizing and deenergizing each group of electrodes. The energizing and deenergizing apparatus includes a high voltage source associated with a respective group and having a control input for turning off the high voltage source wherein the high voltage source provides an output to the group via a current measuring device providing an output indicative of the current measured. A voltage measuring device is connected to the associated group and provides an output indicative of the voltage measured, and quotient forming unit responsive to the outputs of the current measuring device and the voltage measuring device forming a quotient thereof and providing an output when the quotient formed has a predetermined relation to a reference value.

Abstract: In a monitoring system for a bridge output stage which is connected in series with a controllable source of current, to the terminals of a source of operating voltage, the voltage over the bridge output stage and the voltage drop over a current-measurement resistor are fed to a subtraction circuit. The subtraction circuit is connected, via an analog-to-digital converter, to an input of a microcomputer, and a program is provided by which it is tested whether the voltage at the input of the microcomputer lies within a predetermined range. The operating voltage and the voltage over the controllable source of current are preferably fed to a further subtraction circuit the output of which is connected to an output of the subtraction circuit.

Abstract: A water pump protector unit which includes electrical circuitry through which an electric motor is energized. The pump protector unit is primarily adapted for operation of a capacitor-start induction-run electric motor which operates a water pump. The electrical circuitry includes components for energization and deenergization of the start winding of a capacitor-start induction-run electric motor. The electrical circuitry senses the phase angle between the voltage and the current applied to the electric motor. When the phase angle indicates that the electric motor is operating without a load, the circuitry deenergizes the electric motor. Thus, the water pump is protected against damage which may occur when the water pump is operated without pumping water. Preferably, all of the components of the water pump protector unit are housed within a single cabinet.

Abstract: A system and method is disclosed for detecting an abnormality in a network for distributing or transmitting electric power at a predetermined fundamental frequency. The system produces a signal representing the fundamental frequency and another signal representing a harmonic current occurring in the network. The phasor relation between the fundamental voltage and harmonic current representing signal are compared. The system produces a signal indicating the occurrence of a high impedance fault in response to a predetermined change in the compared phasor relationship. Embodiments are disclosed utilizing expression of signals within the network in polar coordinates, as well as embodiments utilizing signals expressed in rectangular coordinates. Such embodiments include circuitry for detecting zero crossing phenomena, as well as circuitry for producing representation of signal products.

Abstract: A monitor for an electric motor, the monitor capable of connection to a supply of electrical energy for the motor, has a microcomputer for measuring the power factor of a voltage applied to the motor and a current flowing to the motor, for storing a desired value of power factor, for comparing a measured value of power factor with the desired value of power factor, and for disconnecting the motor from the supply of electrical energy if the measured value of the power factor differs from the desired value of power factor by an amount that exceeds a predetermined amount. Further, the monitor has means for operating the motor while driving a desired load; means for commanding the microcomputer to measure a power factor of the voltage applied to the motor and the current flowing to the motor while the motor is driving the desired load; and, means for storing the measured value of the power factor, measured while the motor is driving the desired load, as the desired power factor.

Abstract: A method and apparatus for controlling power to a preciptator 27. After each spark the power to the precipitator is reduced to zero, increased along a fast ramp 15 for a fixed period of time and then increased along a slow ramp 17 until a spark occurs. The fast and slow ramp data is computed and stored (memory 48) and then retrieved after each spark. The data retrieved is the data corresponding to the firing angle at the last spark. Apparatus is provided (selector 51 and memory 52) for dividing (frequency divider 45) the retrieved slow ramp data by a number to select the number of sparks per minute. Also the AC current and the AC voltage in the power to the precipitator are detected and the RMS values are obtained (32 and 34) and compared 35 and if the difference is above a predetermined value the power is disconnected (relay 36 and contacts 23 and 24).

Abstract: The present invention comprises a longitudinal differential protective relay for protection and supervision of power line zones in a distribution system. The protective relays are located at each end of the zones that are desired to be monitored. One of the protective relays operates as a master for the other slave protective relays. A TRIP function indicating a line fault in any protected zone is performed by transmitting locally processed measured signals to the central protective relay which determines if and when any measure is to be taken. Each local protective relay comprises a measuring device, a filter and an A/D converter for phase currents and voltages. The digital signals are used to generate a truncated Fourier model of the measured signals in a parameter estimator which cooperates with a frequency estimator and a sampling regulator which, via a synchronization unit, ensures that sampling is performed simultaneously in all protective relays included in the protective system.

Abstract: An underload protection system for an electric motor connected to first and second power supply lines, the lines being connectable to an AC power supply. The system comprises a line voltage sensing circuit connected to the first line and having a line voltage signal impressed therein, and an amplitude adjustment circuit connected to the voltage sensing circuit for adjusting the line voltage signal to produce an amplitude adjusted voltage signal. A line current sensing circuit is connected to the second line and has a line current signal impressed thereon, and a phase adjustment circuit is connected to the current sensing circuit for adjusting the phase of the current signal to produce a phase adjusted current signal.

Abstract: Most power supply regulators either cause the output voltage to drop-off gradually, or caused output oscillation upon reaching or exceeding the limit current. Current limit feedback to an error amplifier within a switching regulator is used to control the output voltage, prevent oscillation, insure that current limiting does not occur until a well-defined threshold is achieved and then steeply limit the current. The circuit uses feedback to the switching regulator to maintain the output voltage within desired limits. The output current flows through the current limit resistor R.sub.c thus providing a voltage proportional to the current at the base-emitter junction of Q.sub.1 via CR.sub.1 and R.sub.2. During normal operation, the forward biased CR.sub.1 voltage maintains a reverse bias on the B-E junction of Q.sub.1. When the voltage across R.sub.c exceeds the forward bias on CR.sub.1, Q.sub.1 turns on, hence turning on Q.sub.