Abstract: An electrical apparatus for visually indicating phase sequence, phase asymmetry and presence of three phases of an AC network comprising two transistors connected by their emitters to a first voltage terminal of the three phase network, the bases of the transistors being connected through diodes to a first voltage terminal and through crosscoupled phase shifting means to two other terminals of the three phase network. The collectors of the transistors are connected through resistors, light emitting diodes and diodes to two other voltage terminals and the emitters of the two transistors are connected through two other light emitting diodes to the first voltage terminal.

Abstract: This specification discloses inventions of a rotation detecting device for a rotary shaft and of a rotation controlling apparatus using this rotation detecting device. The rotation detecting device according to the invention comprises a signal generator for generating two signals vary their amplitude in accordance with the rotation angle of the rotary shaft and have a predetermined phase difference therebetween, part for correcting the respective center voltages output from the signal generator, part for correcting a deviation from the phase deviation between the two signals, and part for correcting the rotating amounts of the rotary shaft on the basis of the corrected two signal. The rotating amounts are represented in terms of rotating angles. A rotating torque can be obtained by calculating a difference between the rotating angles measured at two points apart from each other on the rotary shaft. The rotary shaft can be controlled in accordance with the rotating angle or the rotating torque.

Abstract: A zero phase voltage measuring device for measuring a zero phase voltage of the three phase power system having an earth-fault includes an optic voltage sensor provided at any one of three power lines for detecting a current ground-to-line voltage thereat, a line-to-line voltage sensor provided between any two of the three power lines for detecting a current line-to-line voltage therebetween. A phase shifter and a multiplier are provided for calculating an ideal ground-to-line voltage at the power lines when no earth-fault is observed by changing the phase and multiplying the magnitude of the current line-to-line voltage. A subtracter is further provided to obtain a zero phase voltage signal by subtracting the ideal ground-to-line voltage from the current ground-to-line voltage.

Abstract: A polyphase reversal detection and correction system which operates over a wide range of line frequencies and produces an automatic phase correction for maintaining proper phase sequence to a rotating device. The system includes a circuit arrangement for developing peak integrated signals by comparing the relation of various input phases, and developing an integrated reference phase signal. The input phase signals and the reference phase signals are compared to determine and correct the input phase sequence.

Abstract: Apparatus for determining when two periodic signals are within preselected limits of being in phase, includes square wave generators which convert the periodic signals to pulse trains, and an AND gate which combines the pulse trains to generate a rectangular wave signal having a logic one value when the two pulse trains overlap. A monostable one-shot multivibrator generates clock pulses in response to the leading edge of the rectangular wave signal. A flip-flop latches its output to the logic level of the rectangular wave signal on the trailing edge of the clock pulses. The clock pulses are of a duration representative of the selected phase angle limit, so that the output of the flip-flop is a phase angle acceptance window having a logic 1 value when the difference in phase between the periodic signals is within the selected limits.

Abstract: A method and apparatus are described for determining the charcteristics of an alternating current electrical service at a remote panel as compared with a main panel from which the remote service is connected. The method involves the steps of selecting a line at the main panel and designating it as the reference. The phase relationship of other lines at the main service panel are determined relative to this reference by a process of deriving the period of the signal on the reference line, and from this point the phase relationship of the other line signals are determined. A counter is loaded with a value representative of the derived period of the reference signal, and finally, the characteristics of the individual service line signals at a remote location are determined by a step of comparing each with the characteristics derived for the main service panel.

Abstract: A voltage rotation indicator for testing the phase sequence of live multi-phase electrical power is mounted within a housing. The housing is provided with structure for removably mounting the indicator on a meter box or can during voltage rotation testing. Contact plungers extend from the housing and contact meter jaw test points in the meter box during testing. Field personnel are thus not required to insert their hands into the meter box to attach test clips to the live circuit.

Abstract: A device for monitoring the unbalance of the electric power demanded on the conductive lines of an alternating current network of a three-phase internal installation. The device applies to all networks or three-phase installations which serve single-phase type devices in terms of variable number and power.

Abstract: The invention finds application primarily in three phase power systems having A, B and C voltage phases. The invention includes a first voltage measurement device coupled between the A phase input and the B phase input, having a first measured voltage output. The invention further includes a second voltage measurement device coupled between the A phase input and the C phase input, having a second measured voltage output. The invention also includes a comparator having a first input connected to the first output of the first voltage measurement device and a second input connected to the second output of the second voltage measurement device, for generating a signal when the first measured voltage is equal to and opposite in polarity from the second measured voltage. This signal indicates that a zero crossover event has occurred with the A phase.

Abstract: The present invention discloses electrical testing apparatus to test an AC multiphase supply outlet. The apparatus is located within a flame proof enclosure and provides a visual indication of phase energization, direction of phase rotation, and supply voltage.

Abstract: This invention relates to a voltage sensor for sensing a voltage on an electrically charged object such as a distribution line or the like, the sensor being disposed with an insulation space to the object. The voltage sensor includes an amplifier circuit for outputting a signal having a waveform similar to that of a displacement current inflowing from the electrically charged object via the insulation space, and a filter circuit for extracting a signal having predetermined frequencies from the output of the amplifier circuit and outputting an alternating current waveform similar to the potential of the electrically charged object.

Abstract: The invention interfaces a two-wire 60 Hz circuit to two circuits, each unidirectional, sending and receiving, and carrying frequency modulated audio tones containing the amplitude and phase of the 60 Hz voltage impressed on the 60 Hz circuit. The invention is used to interface differential relays used by electric utilities to detect power transmission line faults to a four-wire voice band communication line.

Abstract: A current-comparator technique for obtaining an instrument for accurate high voltage power measurements at very low power factors is described. The quadrature component of the load current is automatically balanced in the current comparator against a quadrature current obtained from a slave supply, thereby reducing the stringent high accuracy requirement of the instrument when used for measuring power at a very low power factors. The current-comparator-based instrument according to the present invention has an estimated accuracy with respect to its readings of better than 3 percent at 0.001 power factor, 1 percent at 0.005 power factor and 0.5 percent at 0.01 power factor and higher. It features an internal high-voltage active-divider and displays to indicate source voltage, current, power factor and reactance of the load, in addition to the power.

Abstract: A negative sequence occurring in a polyphase power system control including a continuous wave frequency transducer causes a second harmonic to be generated which for a 60 Hz system comprises a 120 Hz signal. In a preferred embodiment of the invention, the continuous wave frequency transducer includes an active 120 Hz notch filter having one stage which provides a component of the 120 Hz second harmonic. This signal is coupled to a second harmonic detector implemented by a semiconductor diode connected to the output of an operational amplifier. The detector diode is coupled to one input of a comparator circuit whose other input is coupled to a selectable DC reference signal. The comparator operates to generate a fault indicating signal indicative of a negative sequence when the output from the second harmonic detector exceeds the reference.

Abstract: The direction of rotation of a three-phase voltage is determined by simultaneous reading of counters triggered by the respective phase zero crossings. Such determination is used in an AC motor drive to dispense of using a tachometer.

Abstract: A current sensor for use in a three phase ac system for producing a signal indicative of the average value of the sum of the squares of the ac current and of the phase imbalance between the three phases using two current transducers and an associated method.

Abstract: A circuit for providing a multiphase digitally synthesized sinusoidal output signal representative of a predetermined symmetrical component set of a multiphase source signal and having a predetermined relationship therewith is taught. The circuit comprises a phase comparator, a phase shifter and a synthesizer. The phase comparator produces an output representative of the phase error in the predetermined phase relationship between the source signal and the output signal. The phase shifter has a variable frequency output for shifting the phase of the synthesized output signal in response to the phase error output signal of the phase comparator. The synthesizer digitally synthesizes at a predetermined amplitude the multiphase sinusoidal output signal. The synthesizer is responsive to the phase shifting output of the phase shifter so as to decrease the phase error between the source signal and output signal.

Abstract: To protect electrical three-phase machines from damage on the appearance of an unbalanced load between the phases, so-called negative sequence current protection is used. Conventional measurement of the negative sequence current takes place in filters which contain frequency dependent LC components. Frequency variations in a three-phase supply, because of an unbalanced frequency response for harmonics in the three phase filters, may lead to an erroneous indication of negative sequence current. The invention provides a novel method for determining both the positive sequence and the negative sequence currents to a three-phase load. For grounded systems the zero-sequence current is eliminated. Measuring each phase current (I.sub.R, I.sub.S, I.sub.T) and the phase sequence, the positive sequence and/or negative sequence current are/is determined as the solution of an equation derived in advance from the electrical relationships between the phase currents.

Abstract: A phase detector for monitoring the presence, sequence and polarity of each phase line for a three-phase power input and indicating when a phase is missing or out of sequence.

Abstract: A protective relay for detecting power arcing faults on a three-phase electrical power spot network. A phase-to-phase power arc on a spot network produces harmonics on the phase-to-phase voltages, and the phase currents; a phase-to-ground arc produces harmonics on the phase-to-neutral voltages. The protective relay of the present invention monitors one or more of the three phase-to-phase voltages, the three phase-to-neutral voltages, or the three phase currents and indicates a fault based on the harmonic content of those signals.

Abstract: A waveform crossing detector circuit for a pair of waveforms of a three-phase AC supply applied to respective input terminals (7,8,9). The circuit includes a pair of opto-couplers (1,3; 2,4) for isolating an output terminal (21) from the supply. In order to obtain an accurate indication of the instants of crossing the light-emitting diodes (1,2) of the couplers are driven by respective transistors (5,6) which act as the actual crossing detectors. The collector circuits of these transistors are driven from the third phase, the potential of which is at a maximum when the relevant instants occur. Two further such arrangements may be connected to the taps (22,23,24) of an input potential divider in a cyclical manner and the output signals of the three resulting arrangements combined by means of logic gates to produce pulses which occur once every 60.degree. of the input waveform.

Abstract: A three-phase symmetrical component active band-pass filter includes three 120.degree. phase shift circuits which are connected in a closed loop fashion such that each phase shift circuit receives an input signal from one phase of an associated power system and a second signal from the output of one of the other phase shift circuits. A voltage tunable filter is formed by using multipliers to couple some fraction of the output of each phase shift circuit to a summing point at the input of another phase shift circuit. Phase comparators and an integrator can be added to achieve a self-tracking tuning arrangement.

Abstract: A method of detecting symmetrical components of a three-phase supply-line voltage comprises the steps of converting three-phase voltage to alternating single-phase voltage with the aid of at least two function generators (2), (3), with at least one of said function generators being an active-reactive circuit, which conversion of a three-phase voltage is effected by altering said supply-line voltage in amplitude and phase in said active-reactive circuits, and subsequently summing up output voltages of the function generators (2), (3), to produce symmetrical components of said three-phase voltage, forming a control signal proportional to a disturbance influencing the output voltages of the active-reactive circuits (4) and compensating said disturbance influence by control action, wherein according to the invention said control signal is formed from the difference in voltage drop between elements (5), (6) in each active-reactive circuit, and compensating said disturbance influence is done by summing up said cont

Abstract: Disclosed is a phase sequence network. The network is compensated for frequency variations in the signal applied to the sequence network so as to develop a desired sequence component output that is accurate over a limited but adequate range of frequencies.

Abstract: An electronic phase-sequence indicator for indicating the cyclic sequence order for three-phase electric systems using a single-phase indicator-detector having an ammeter circuit and a voltmeter circuit interconnected to the three-phase system with resistors and capacitors, or alternatively with inductances and capacitors. The voltmeter moving element is placed between the pole pieces of a ferromagnetic circuit and is composed of a small freely rotatable frame, upon which the voltmeter small coil is wound and which is composed of many turns of a very thin copper wire. Upon the axle of the small frame two spiral springs are mounted having the functions of determining the counteracting torque and of conveying the voltmeter current to the small coil.

Abstract: An unbalanced current detector for a three phase electrical system of the type including a current transformer (4, 6, 8) for each phase (.phi.A, .phi.B, .phi.C) and a burden resistor (16) which receives a rectified output of the current transformer is disclosed. The harmonic content of a rectified ripple voltage developed across the burden resistor (16) is applied to a filter (20) for extracting desired frequencies and rejecting other frequencies, and the filter output is applied to a level detecting and amplifying circuit (54) the output of which is applied to an indicator (77) to indicate an unbalanced current condition.

Abstract: Negative sequence filters employing one to three operational amplifiers and a single reactive element generate the negative sequence voltage of a three phase AC power system by generating two line-to-line voltages, phase shifting one of them to bring them into phase and summing the resultant signals. The phase shifting circuit includes a potentiometer, one end of which serves as the input to the circuit and the other end of which is connected to the inverting input of an operational amplifier. A capacitor is connected between the tap point of the potentiometer and ground and the values of the components are selected so that the tap point of the potentiometer can be positioned to compensate for variations in the capacitive reactance of the capacitor without affecting the magnitude of the phase shifted signal.

Abstract: Sequence network circuits are provided for use in three-phase protective relaying applications. In one embodiment, the circuit includes input circuit means for receiving input signals, one of which comprises a reference input signal, and signal processing means for processing such input signals. The signal processing means includes an operational amplifier and a single capacitor. A plurality of resistors couple the input signals to the operational amplifier. The value of the resistors and the capacitor are selected such that the output signal of the operational amplifier is representative of the quadrature voltage, relative to the reference input signal, and shifted 90.degree. lagging with respect to its normal phase position. Other embodiments are disclosed.

Abstract: A portable phase angle meter instrument for use on electric utility power distribution systems.A portable phase angle meter instrument is interconnected between two distribution conductors to generate a voltage signal and current signal substantially in phase with the voltage across the conductors and the current in one of the conductors respectively. A potential probe with a conductive hook for interconnection to a first conductor, houses a first capacitor. A current probe assembly housing a second capacitor, has a head for interconnection to a reference conductor. The head has a Hall sensor or a transformer sensor for generating a current signal substantially in phase with the reference conductor current, and a plate for making electrical contact with the reference conductor. The capacitors are interconnected in series between the plate and the hook via a high voltage cable.

Abstract: A circuit arrangement for monitoring the phase sequence of a rotary field includes a voltage comparator which is provided and which receives one half-waves from two phases and the other half-wave of a third phase is fed, inverted, to its first input in order to form a measuring voltage and a non-inverted half-wave is fed to a second input as a reference voltage. The voltage comparator is adjusted so that it emits an error signal which characterizes an erroneous phase sequence when the reference voltage exceeds the measuring voltage.

Abstract: An improved solid state power factor monitoring device is disclosed. The device is isolated from the operator and requires no grounding lead or other direct connection to ground for monitoring power factor in high voltage alternating current carrying power lines. A zero crossing switch is used in combination with sensors and amplifiers to actuate a counter to determine the phase relation between current and voltage in the conductor as a representation of power factor.

Abstract: A three-phase electrical transformer utilizes a conductor independent of the transformer windings for sensing zero sequence current upon the occurrence of a ground fault. A current transformer coupled with the independent conductor provides polarization to protective relay devices. One embodiment utilizes the transformer internal tank shield in combination with the current transformer for providing zero sequence current.

Abstract: A method of monitoring open phase, phase reversal and voltage unbalance conditions in a polyphase source includes shifting the phase of signals which are proportional to the line voltages in a three-phase A.C. power source by 180.degree., +60.degree., and -60.degree., respectively, and summing the phase-shifted signals to generate a signal which is proportional to the negative-sequence component of the three-phase line voltage. This signal is rectified and compared with a reference signal. If a net negative-sequence signal is generated over a sufficient time period a positive output signal decreases until it crosses a switching threshold to disconnect a load from the source. The output signal will not rise again to the switching threshold, thereby allowing reconnection of the load, until the negative-sequence signal subsides and is less than the reference signal. A circuit is disclosed with three operational amplifiers and two passive filters to carry out the invented method.

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: An electronic circuit breaker (low voltage) device having three lead wires connected to the line side of the device, and four lead wires connected to two lamps, each of which is connected by two of the last said wires, the device being fitted into a small case and serving to test the voltage of electrical circuits.

Abstract: Apparatus for detecting the direction of motion from a reference signal, R, and a quadrature signal, Q, derived from the output signals X+0 and X+90 of a position transducer, wherein the polarity of the reference signal alternates with every fixed increment of motion of a transducer and the quadrature signal which maintains phase difference of +90.degree. or -90.degree. with respect to the reference signal depending on the direction of motion, is comprised of: digital means for producing a narrow pulse, P, at each low-to-high transition of the quadrature signal and a narrow pulse, N, at each high-to-low transition of the quadrature signal; means for determining the direction of motion from these narrow pulses and the reference signal once during each half cycle of the reference signal, and means for storing this direction information until a subsequent determination is made in order to provide a continuous signal indicating the direction of motion.

Abstract: A method and apparatus are disclosed for accurately determining negative sequence current in a three-phase turbine-driven generator, the currents indicative of power oscillations and of torques harmful to turbine buckets. A signal conditioner and phase-shifter network are described which provide precise amplitude and phase angle adjustments and null balancing features which permit accurate determination of the magnitude of negative sequence current even though this current is a very small quantity determined as the difference between two large signals.

Abstract: A local power source, such as a battery, is connected to a tone generator oscillator circuit which includes an audio reproducer. The tone generator includes a voltage sensing element such as a dark-resistance photoconductor, a resistor, or a Zener diode, at which the voltage is sensed when connected in a phase sequence circuit network or other network to be tested. The output tone, whether present or not, is indicative of a predetermined phase sequence of connection of test terminals. A transfer switch can connect the oscillator directly or through dropping resistors or non-linear resistances such as a Zener diode to the test terimals so that the test terminals can also be used to test for external resistance, short circuits, or polarity of applied voltages in the network which, depending on their polarity, may introduce external voltages, thus modifying the tone of oscillation of the tone generator.

Abstract: Sequence analyzers or wave filters having resistance and capacitance elements only, for providing output signals having a magnitude proportional to the magnitude of the positive or negative sequence symmetrical component of a three-phase power source. By eliminating the need for inductors or transformers substantial reductions in size, weight and cost are realized. Four, five and eight element embodiments are disclosed, the latter providing an output referenced to the power system neutral.

Abstract: For measuring and indicating phase voltage, phase sequence and other electrical values in a three-phase power system, and electrical values in single-phase and DC systems, a unitary instrument or apparatus includes a meter movement and three phase-resistors of equal value which are connected to a common juncture defining a neutral point, with a first phase-resistor connected in series with the meter. The three phases of the external circuit to be tested are connected respectively to the three phase-resistors through a three-pole three-position selector switch for selecting the three different phase to "phase-resistor" relationships. A switch connected between a third phase-resistor and the common juncture performs the alternative functions of opening or closing this circuit.

Abstract: A temporary or portable electrical distribution system includes a distribution box supplied with power by a flexible cable. Field repairs carelessly made or other causes may result in wires being transposed or open. To eliminate hazards and to ensure proper operation of equipment, sensing means including simple circuitry in the distribution box prevents operation of a master box switch except upon the verification of proper wiring.

Abstract: Circuitry is utilized to interconnect loads to the power distribution system and only conducts current when voltage conditions from the system are appropriate. Therefore, the load is deenergized whenever reversed connections are made to the power distribution system, or whenever an open circuit exists in any line thereof. Latching means can be included in the circuitry to continually energize the load when an open circuit develops in either nongrounded or hot line of the power distribution system after the load has been initially energized therefrom. Furthermore, the effect of the latching means is externally controlled through a switching means so that remote circuit conditions can be synchronized therewith. When an indicating means is incorporated as the load, the circuitry functions as a detector and when the circuitry is utilized with a circuit breaker to deenergize the load, ground fault protection can be incorporated therewith.