Showing papers on "Three-phase published in 1982"

Harmonic Power Flow Studies Part I - Formulation and Solution

Abstract: The conventional Newton-Raphson power flow study has been reformulated to permit the inclusion of nonlinear loads. These loads give rise to harmonic signals which propagate throughout the power system. The reformulation is based on the reduction to zero of the mismatch active power and reactive voltamperes, the imbalance current at harmonic frequencies, and the mismatch apparent Voltamperes. Conclusions on the existence of positive, negative, and zero sequence signals are made for harmonic frequencies. The harmonic power flow study formulation is illustrated for a three phase full wave bridge rectifier. A companion paper presents a discussion of the actual computer implementation and several practical examples.

Matrix Representation of Three-Phase N-Winding Transformers for Steady-State and Transient Studies

Abstract: Detailed transformer representations are needed in the analysis of electromagnetic transients and in the analysis of unbalanced steady-state conditions. This paper describes the derivation of mdels for three- phase and single-phase N-winding transformers in the form of branch impedance or admittance matrices, which can be calculated from available test data of positive and zero sequence short-circuit and excitation tests. The models can be used for many types of studies as long as the frequencies are low enough so that capacitances in the transformer can be ignored. The inclusion of saturation effects is briefly discussed.

Power line communications bypass around delta-wye transformer

Abstract: Circuits for bi-directionally bypassing a delta-wye transformer with a balanced phase-to-neutral power line communication signal, using passive components. The circuits include a set of three capacitors connected in a wye configuration, each having one side connected to one of the three-phase power lines on the delta side of the transformer. The circuit further includes a network connected from the node of the wye configuration of capacitors to neutral, the network including an inductive reactor with one side connected to neutral and the other connected to the node of the wye windings of the transformer. Component values are selected so that the circuit is resonant from the three phase lines on the delta side of the transformer to neutral. Further, the voltage transformation ratio of the communication signal from the delta side to the wye side is made the same as the corresponding power voltage ratio of the transformer.

Device for parallel supply into an AC or three-phase network

Abstract: In order to synchronise a final control element (an invertor (2) supplied, for example, from a solar generator (1) or an externally driven synchronous machine) to a network (11) to be supplied, both the magnitudes (¦Uw¦, ¦Un¦) and the directions of the corresponding voltage vectors are determined by means of coordinate converters (21, 31) and vector analysers (22, 32) from the final control element output voltage (Uw) and the network voltage (Un). The difference (¦Un¦-¦Uw¦) of the magnitudes is supplied via a magnitude controller (30) to the amplitude control input (3) of the final control element. A vector rotator (25) forms the angle between the vectors, which angle can be controlled to zero by a phase controller (33) acting on the frequency control input (4) of the final control element (2). In order to keep the final control element in synchronism with the network after closing the synchronising switch (14), and to control the exchange of real power and reactive power at the fundamental frequency between the mains and the final control element, the real component and the reactive component are determined from the measured current value (Iw) by means of a coordinate converter (41) and a vector rotator (42) and are each supplied to a controller (43, 44). The output signal of the real current controller is also connected to the phase controller input, and the output signal of the reactive power controller (43) is additionally connected to the magnitude controller input. This results in a universal apparatus which facilitates both network synchronisation and maintenance of a network-synchronous parallel operation of the final control element, while also facilitating the transition to an externally synchronised supply into a passive consumer network (isolated operation).

An AC to DC converter with high quality input waveforms

Abstract: An ac to dc converter which draws sinusoidal and in phase current waveforms from the ac power source is described. Harmonic and power factor measurements obtained from an FET converter operating at 45 kHz for a single phase and a three phase connection are presented. A stability analysis and design methodology is given.

Brushless three phase direct current motor control circuit

Abstract: A driver circuit is coupled to the stator windings of a brushless three phase DC motor which is responsive to the open circuit back EMF voltage induced in the next stator winding to be energized as a permanent magnet rotor of the motor is caused to be rotated for producing phase current drive to the stator winding in synchronous with the operation of the motor. The driver circuit includes an increment drive circuit for supplying periodic switching command signals in succession to a switching circuit to produce phase current drive in each stator. The increment drive circuit increments a switch command signal to cause phase current through the next phase stator winding in reference to the magnitude of the EMF voltage induced across said phase stator winding falling below a reference level. A feature of the invention is that the frequency of the periodic switch command signals is varied during starting of the motor dependent on the magnitude of starting potential supplied to the driver circuit to prevent the motor from "locking" which would otherwise inhibit start thereof.

Twelve pulse load commutated inverter drive system

Abstract: A control system for powering an AC load such as a polyphase synchronous motor having at least two sets of three phase (3φ) windings. Each three phase winding set is powered by an independently operable six pulse load commutated inverter drive including a source side converter and a load side converter coupled together by means of a DC link and wherein the source side converter and the load side converter are operated in accordance with respective current and load angle regulators which respond to torque command signals generated by speed regulators. The two motor drives operate concurrently in separate control channels which are substantially independent of one another with the exception that in one embodiment, which is the preferred embodiment, the speed regulator and the motor terminal overvoltage regulator are cross-coupled to effect a balanced torque command and motor terminal voltage from each channel while still providing for continued motor operation by one of the motor drive channels in the event that the other becomes inoperative for any reason. In a second embodiment, one of two redundant speed regulators is adapted to provide a common torque command to both channels with the other speed regulator taking over in the event of the failure of said one speed regulator.

Microprocessor-Based Design of a Firing Circuit for Three-Phase Full-Wave Thyristor Dual Converter

Abstract: A firing scheme based on a microprocessor to control an antiparallel-connected three-phase thyristor dual converter is presented. Using table-look-up algorithm to speed up the response, it gives a full range control of the firing angle between 0° and 180° for both positive and negative current control. The maximum time delay required to correct the firing angle is one-sixth period of the ac power source. The firing angle between 120° and 180° is used for the regeneration braking to achieve the required dynamic performance in four quadrants. Built with all digital circuits with no further adjustment, this system is more reliable and has lower cost.

Control system for controlling an scr network to regulate three-phase a-c power flow

Abstract: The power delivered from a three-phase A-C power source and through a network of SCR's (connected, for example, to form a full wave rectifier bridge or to provide an A-C switch) to a load circuit is adjusted by controlling the conduction angles of the SCR's. The control is achieved by developing, from only one of the three alternating phase voltages provided by the A-C power supply, a reference square wave signal of the same frequency and whose amplitude excursions are precisely synchronized or keyed to the zero voltage crossings of the selected phase voltage, even though that phase voltage may include undesired harmonics, noise, transients or other distortion components. Since the influence of the undesired signal components has now been eliminated and since the reference square wave signal also has a fixed phase relationship with the other two phase voltages, logic circuitry may be controlled by the reference square wave signal, and by a d-c control voltage representing a desired power flow to the load circuit, to produce gating signals for triggering the SCR's into conduction at the angles required to translate the desired power to the load circuit. With this arrangement, control of all three phases is made immune to undesired signal components in any of the phase voltages.

Three-phase winding in a mixed star-delta circuit for an electrical machine

Abstract: In a fractional-pitch three-phase winding in a mixed star-delta circuit for stators or slipring rotors of an electrical machine, in order to reduce the harmonic components and the copper losses, the inner winding sections are connected by means of equalising conductors in a delta circuit to which in each case two parallel, outer winding sections are connected, in the form of a star, which are offset by 30 DEG electrical with respect to the delta sections and are connected to the terminals. The spatial splitting of the winding sections is carried out in this case such that a twelve-zone winding arrangement is produced within each pole pair.

Three phase square wave welding power supply

Abstract: In a three phase welding power supply, the three phase power is connected to a welding arc by a power control circuit having three conducting paths for straight polarity current and three conducting paths for reverse polarity current. The power control circuit comprises a three phase bridge rectifier circuit having eight bridge arms each including a silicon controlled rectifier with the bridge circuit being connected between the three phase power source and the welding arc which is in turn connected to the three phase power supply neutral. An inductor is connected across the direct current terminals of the bridge circuit so that arc current flows in one direction through the inductor regardless of the polarity of the arc current. The conducting paths are selectively activated at non-zero voltage points to conduct repetitive sequences of independent numbers of straight polarity half cycles of arc current followed by independent numbers of reverse polarity half cycles of arc current to the welding arc. Pulses are generated in synchronism with each of the three power phases and counted to determine the activation sequences of the conducting paths. By controlling the generation of the pulses and the counts of the pulses at which the paths are activated, a variety of sequences are generated.

Circuit for generating a rotating field for a three phase synchronous motor serving as a flywheel starter for a vehicle internal combustion engine

Abstract: In combination with a brushless, three phase synchronous motor forming part of a flywheel starter of an internal combustion engine and having a stator with field windings and a winding-free toothed rotor having a pole pitch angle, a circuit for generating a rotating field for the windings is disclosed. The circuit includes a sensor positioned near the rotor for generating signals indicative of the pole pitch time of the rotor. A divider circuit is provided for generating a current flow signal for each field winding in response to the sensor signals. A delay network is coupled to the divider circuit and determines a time delay between the start of the pole pitch time and the start of the current flow signals.

Circuit arrangement for monitoring a balanced (symmetrical) three-phase alternating current

Abstract: In order to protect loads and to ensure the operation of connected apparatuses, it is necessary to monitor a three-phase alternating current for the rotation direction of the phases being incorrect and for failure of phases. A circuit arrangement is specified for this purpose which, in addition, also emits digital signals at the output, which signals can be evaluated by digital circuits. A zero-crossing detector is arranged in each phase of the three-phase system and consists of an optocoupler (which is located in the bridge arm of a rectifier circuit) and of a pulse-former stage which emits the digital zero-crossing signal (ZVD). The zero-crossing signals (ZVD) are supplied to a three-phase (rotating-field) monitoring circuit which confirms whether a zero-crossing signal from the third phase has occurred between two zero-crossing signals which are associated with successive phases. If this is the case, then there is a defect in the rotation direction of the phases. The zero-crossing signals (ZVD) are furthermore supplied to a phase-failure monitoring circuit which emits a defect signal if zero-crossing signals allocated to two different phases occur simultaneously. The circuit arrangement can be used for both star-connected circuits and for delta-connected circuits.

Microprocessor-implemented digital filters for the calculation of symmetrical components

Abstract: Symmetrical components of voltages and currents of three-phase power systems are used for protection purposes and power-system automatic control. Until now, passive and active analogue filters have been used for determining the symmetrical components from the phase quantities. A disadvantage of analogue filters can be the fact that it is difficult to suppress harmonic components that may be present in the phase quantities. It will be demonstrated that very suitable digital filters can be implemented with a microprocessor which are able to suppress the second- and third-harmonic components as well as the DC components that are present in the measured signals. Tue input of these digital filters consists of three phase quantities and the output consists of three numbers representing the amplitude of the zero-, positive- and negative-sequence quantities.

Three-phase circuits with voltage control by integral-cycle single-phase mode triggering of thyristors

Abstract: Several configurations of balanced three-phase series RL loads are investigated to consider the feasibility of using thyristor control with integral-cycle triggering. The four-wire star-connected load, with pairs of thyristors in the supply lines and the delta-connection with pairs of thyristors in the load legs, are found to be suitable. Both connections result in similar load voltage and current waveforms. The branch-delta connection is considered to be preferable because the supply lines do not contain DC components of current.

Network coupling for exchanging electrical energy between a three-phase network at a higher frequency and a single-phase network at a lower frequency

Abstract: The object exists for a device for exchanging electrical energy between a three-phase network at a higher frequency and a single-phase network or a single-phase load at a lower frequency to make it possible to exchange energy at high power without any disturbing feedback. This object is achieved by a three-phase direct converter (7, 8, 9) which is connected to the supply network as a star circuit and whose phase voltages (U1, U2, U3) are formed by the series connection of two reversing converters (71, 72; 81, 82; 91, 92), the first phase output of the direct converter (1) being connected directly to a connection on the primary side of the single-phase transformer (10), the second phase output (2) being connected via an inductor coil (5) and the third phase output (3) being connected via a circulating current inductor coil (61) and a series-connected capacitor (62) to said connection on the primary side of the single-phase transformer (10), and the star point of the direct converter being connected to the other connection on the primary side of this transformer, which is coupled on the secondary side to the single-phase network or to the single-phase load (12). The field of application is especially the supply of a railway network.

Three-phase alternator with dual armature winding.

Abstract: Three-phase alternator with dual armature winding. In this alternator, the armature winding consists of two three-phase windings 2, 3, coupled as a star. Each three-phase winding 2, 3 is connected, by three connections 4a, 4b, 4c; 8a, 8b, 8c, to the inputs of a rectifier bridge 5, 9 with six diodes, the positive and negative outputs of the two bridges 5, 9 being interconnected so as to produce a coupling in parallel. The central points 16, 17 of the two three-phase windings 2, 3 are connected to a bridge of additional diodes 19, 20, which is mounted in parallel with the two main bridges 5, 9, and permits the harmonics of the phase currents to be rectified. Application to low power alternators, in particular for motor vehicles.

Power factor regulating method for connection of a capacitor to a line and apparatus embodying the method

Abstract: Power factor regulating method and an apparatus embodying the method in which each of three condensers, which are to be connected to each phase of a three phase distribution line, is preliminarily charged with approximately peak line voltage while a load connected to a distribution line is opened in order to lessen impulse waves that are brought about at the time of connection of the condenser to the appropriate phase of the power line. The present method needs no conventional discharging coil.

Surface processing method by ion bombarding

Abstract: PURPOSE:To eliminate any remarkable scratch due to abnormal discharge in case of a surface processing of a substrate by ion bombardment by a method wherein a pulse voltage is impressed on the substrate. CONSTITUTION:An electron beam generating source 2 and a substrate 3 are opposingly arranged and a probe 4 is arranged between them while a filament 5 is provided on the side opposing to the probe 4 within a bell jar 1. A power supply circuit 11 which is provided to be used on AC or DC by switching (a), is provided to impress negative voltage to the substrate 3 under the earth voltage. The power supply circuit 11 can transferably output negative DC voltage with three phase all wave rectified form and negative pulse voltage rectified single phase half wave mode out of three phases only. In case of ion bombardment, the pulse voltage is impressed on the substrate 3 while in case of ion plating, DC voltage is impressed on the same.

Resistance welding machine

Abstract: PURPOSE:To increase capacity without receiving restriction in switching elements and electric power sources by connecting the primary side of welding transformers to a three phase AC power source and interposing a switching element between at least one of the transformers and the three-phase AC power source. CONSTITUTION:If bidirectional thyristors 29, 30 are made nonconductive, and saturable reactors 24, 26 are put in a satd. state by control means, the voltages of the same polarity are applied respectively to a primary winding 18 from an electric power source 20 and to a primary winding 22 from an electric power source 28. The voltages of the same polarity are also induced in secondary windings 6, 8. Since these windings 6, 8 are connected in series, the induced voltage are added, and welding current flows between welding electrodes 10, 12, whereby objects 14, 16 to be welded are welded. Hence, the resistance welding machine of good rising characteristics of welding current and large capacity is produced inexpensively without receiving restriction in the capacity of the reactors 24, 26.

Three-phase power transmission line phase-to-ground fault responder

Abstract: A three-phase power transmission line phase-to-ground fault responder wherein voltage coils of respective responder relays are energized by respective phase-related voltages and wherein current coils of such relays are serially connected across the composite voltage source comprising the three serially composite voltage source comprising the respective phase-related voltages applied in series. In one embodiment the phase-related voltages are proportional to the transmission line phase voltage itself whereas in a second embodiment, less sensitive to location of fault in relation to the instrument takeoff voltage location, the phase-related voltage is the vector sum of voltages of the other two phases.

A novel continuously variable single to three phase load matching circuit

Abstract: This paper describes a continuously variable single to three phase load matching circuit. The phase balancer is realized using two thyristor controlled inductors together with a fixed capacitor bank. It is designed to balance a variable single phase load on the three phase supply network. The paper provides a simple analysis of the phase balancer and a novel method of realizing disjoint closed loop control of the two thyristor-pair firing angles is described. The implementation of the closed loop control using a M6809 microprocessor is briefly outlined and experimental results obtained with a laboratory scale prototype are included.

Three=phase electric arc furnace - with rectangular hearth and six electrodes or multiple of six in specified circuitry

Abstract: A three-phase electric arc furnace for smelting or redn purposes, esp in the prodn of ferro- or silicon alloys has a rectangular hearth with six electrodes or a multiple of six which are arranged in two rows, with each pair at the corners of an imaginary square with the adjacent pair The electrode spacing is chosen to produce a coherent active bath surface across the entire hearth area All electrodes are connected to a number of three-phase systems which equals one-third of their total number The heavy current bus bars are connected in series with the transformer sec windings via the electrodes such that the latter are the corners of a delta circuit This furnace has a capacity much greater than can be reached with conventional furnaces and it has a higher electrothermal efficiency The bath is loaded uniformly and the electrical system is symmetrical The electrodes operate independently of each other and the furnace has lower operating costs

Three phase autotransformer

Abstract: PURPOSE:To contrive compactness and light weight for expanding the capacity of the limit to transformer transportation and to obtain the constant voltage of low-voltage tertiary windings and the freedom of delta and star connections by a method wherein the built-in winding in each phase is composed of delta connection in isolating a LVR section with tertiary winding from a main transformer section. CONSTITUTION:The main transformer 11 section in each phase is composed by winding a built-in winding 10 with a series winding 14 and shunt winding 15 on at least one iron core leg. Meanwhile, each voltage regulator 12 at on-load is composed by winding a tap winding 6, exciting winding 7, and low-voltage tertiary winding 8 on at least one iron core leg. In this way, as the built-in winding 10 in each phase is composed of delta connection, a problem on the third harmonic wave is solved and no zero-phase current flows to the outside even if operation is made by the main transformer 11 in each phase only. Accordingly, no induction fault to communication lines occurs. As zero-phase impedance is also decreased, fault current becomes high. Therefore, detection sensitivity will not decrease.

Electrically heated vacuum furnace with a fault detection system

Abstract: An electrically heated vacuum furnace is described as having a fault detection system which has the ability to sense among other things, carbon arc buildup, a load touching a heating element, short circuits from broken heating elements, and short circuits in any heating element connection whether it be single phase, three phase delta or three phase wye connections. The system essentially comprises an electrically balanced wheatstone bridge which is in a main circuit in parallel with the electric heating element and the grounded casing of the furnace. A switching mechanism maintains the circuit in a normally open condition. A timer is provided to periodically disrupt the flow of electric current to the electric heating element in the furnace. The switching mechanism will be operated to close the circuit if the circuit is free of electric current. Should any of the aforementioned faults occur, the bridge will be thrown out of balance so that there will be a small leakage of current which is detected and utilized in the shutting down of the furnace in cases where the fault is severe and necessitates stopping the operation of the furnace.

Three-phase current transformer for gas-insulated pipe type bus line

Abstract: PURPOSE:To reduce the total dimensions of a set of current transformers, by a method wherein three-phase conductors are so arranged to form an equilateral right triangle and the two transformers on the phases of the larger phase distance are placed at the same position of the direction of the conductor axis and another transformer on another phase is placed at the position shifted from that of the other two CONSTITUTION:A pipe-type busline is composed of a casing 21 and three-phase conductors 22, 23, 24 inserted in the casing 21 and so arranged to form an equilateral right triangle These three-phase conductors 22, 23, 24 are supported by a three- phase insulating spacer 25 Two current transformers 31, 32 which are inserted on the two-phase conductors of the larger phase distance are placed around the shields 29a, 29b, 29c of a flange 29 so as to be parallel to each other And another transformer 30 on another phase conductor is placed at the shield 27a of a flange 27 Thus the transformers 31, 32 are placed at the position shifted from that of the other two With the above method the phase interval of the conductors is securely maintained and as the shields 27a, 27b, 27c and 29a, 29b, 29c are so arranged to face each other, the interal between the facing surfaces can be reduced, so that the dimensions of the total configuration can be reduced

Controlling method of multiplied inverter

Abstract: PURPOSE:To reduce ripple of torque when an electric motor is to be driven with low frequency by a method wherein the pulse width modulation system is taken into multiplied inverters, and the outputted wave form is made to approach to a sinusoidal wave much more. CONSTITUTION:At the multiplied inverters wherein inverter circuit 10, 20 being connected respectively in three phase bridge are connected in parallel, and corresponding switching elements in the respective inverter circuits are controlled as to make currents to flow having the prescribed phase difference alpha, the total of the period to perform pulse width modulation on the output voltage or on the output current by making one switching element in the inverter circuits 10, 20 to repeat ON-OFF action alternately with another switching element in the same inverter circuit in the period of one cycle of output of the inverter is so controlled as not to exceed two times of phase difference alpha. Accordingly smooth operation of the motor having little ripple of torque can be held even when the motor is to be driven with extremely low frequency.

Combined IC engine and electric motor drive for crane - uses flywheel to collect energy output from engine during crane load descent

Abstract: The floating crane uses an internal combustion engine driven generator to supply electric motors which perform the crane functions. When the crane load is descending the excess energy output by the engine is stored in a flywheel and is recovered when the generator is next loaded. The internal combustion engine can then operate at constant speed. The internal combustion engine drives both a 50Hz generator which supplies the crane auxiliaries and also the lifting generator which is coupled through a free wheel mechanism and gearing to a shaft carrying a flywheel. The three phase AC lifting generator is coupled to the flywheel, and generates a voltage which is passed to various electric motors through thyristor controllers. An auxiliary internal combustion engine drives a generator feeding a pony motor to start the main motor.

Generating method for plasma arc

Abstract: PURPOSE:To generate plasma arcs with plural phase AC voltages of low voltages without requiring intricate devices by applying the AC voltages between many non-consumable electrodes provided in the gaseous cup of a plasma welding torch and between the respective electrodes and base materials. CONSTITUTION:Three pieces of electrodes 29, 31, 33 such as W welding rods are disposed in a gaseous cup 35 at equal intervals in extreme proximity to each other so as to permit generation of inter-electrode arcs and in parallel in a triangular shape toward a nozzle port 28, thereby constituting a TIG torch 37. Three phase AC electric power is supplied between these three electrodes, and further base materials 39 are connected to the neutral point of said three phase AC electric power. Thereby, three interphase arcs 41 are generated among the electrodes, and arcs 43 are also generated between the materials 39 and the respective electrodes, thus six pieces of the arcs are generated simultaneously at the leading end of the torch 37. As a result, the central part in the leading end of the torch is heated to extremely high temp. and plasma 47 is generated between the same and the materials 39. This plasma is generated simply by supplying about 35V electric power and feeding gaseous Ar to the cup 35.