Showing papers on "Three-phase published in 1977"

Non-interruptible power supply systems

Abstract: A non-interruptible power system (NIPS) for generating polyphase A.C. of a substantially constant desired frequency and a substantially constant selected voltage, comprising: (A) a source of interruptible power and a motor energized thereby, (B) a novel generator for producing the desired polyphase A.C. driven by the motor, the generator comprising a plurality of field cores each having a cylindrical surface with a layer of magnetizable permanent magnetic material thereon, cooperatively juxtaposed wound stators each with an excitation coil therein for magnetizing an adjacent layer of permanent magnetic material into a pattern of magnetic poles and at a high remanent flux density, modifying windings for changing the remanent flux density in such pole pattern, supplementing windings for energizing the excitation coil, and primary potential generating windings in slots in the stator, a source of exciter current, and electrical control means for the generator, (C) the generator producing the desired substantially constant frequency A.C. at the desired voltage regardless of variations in the motor speed and even for a brief period of time when the source of power to the motor is interrupted by converting a part of its rotational energy to A.C. output, and leading windings, alone, or with lagging windings, in each of the wound stators having the primary windings, the leading and lagging windings being placed in such positions that, in a three-stator generator, they will each generate a single phase A.C. potential from about 110° to 115° out of phase with the single phase A.C. generated by the primary windings in the same stator, but the A.C. potentials of the leading windings and lagging windings of one stator will each be synchronous with the single phase A.C. potential developed in the other stators' primary windings, thereby obtaining three phase A.C. having a low total harmonic distortion.

Motor protective device

Abstract: An electrical device is connected to the magnetic starter of an electrical motor to protect the motor windings from a loss of power on one or more input lines of a three phase power source. The device includes two transformers each being connected across two input lines and having one input line in common with each other. The transformer secondaries are each connected in a relay circuit so that a voltage on the secondary of each transformer above a predetermined value will actuate the relay in its respective circuit. The contacts of both relays are connected in series with each other and with the magnetic starter of the electrical motor so as to actuate the magnetic starter when both relays are closed. When the voltage on any of the three input lines drops substantially below a normal operating level, one or both of these relays will open, immediately turning off the magnetic starter and shutting down the motor to prevent damage to the motor windings. The transformer primary windings are connected through a terminal strip to the power source to enable series or parallel connections to accommodate both 240 volt and 480 volt power lines.

Three phase electrical power ozone generating system

Abstract: A three phase power ozonator system in which the head of an ozonator cell containing multiple cylindrical type elements is tri-partitioned to define three sectors in the cell each of which contains a portion of the total number of cylindrical type dielectric elements. The partitions are made of insulating material such as polyvinyl chloride. Each sector is distinct and each sector is adapted to be operated with single phase electrical power. As a result the ozonator cell as a whole is able to operate using three phase electrical power. This arrangement allows for the operation of the ozonator cell in a system having any number of other three phase electrically operated components of equal or smaller electrical load than the ozonator cell in such a way that a balanced electrical load is maintained throughout the system. An electrical supply and control sub-system including a three phase power transformer, current sensors for each electrical sector and voltage sensor for one sector, current and voltage comparators and a variable transformer driven by a reversible electric motor, provides current to the electrodes in all sectors, monitors the current in all phases and turns off the electrical supply if significant imbalances among the sectors are detected.

Variable reactance transformer

Abstract: An improved saturable reactance transformer having a main core and a pair of adjacent auxiliary cores is disclosed. The auxiliary cores carry DC control windings which regulate the reactance of the main core which carries the secondary, or output windings of the transformer. The primary winding is wound around all three cores, with the amplitude of the control voltage applied to the control windings regulating the output of the secondary windings. To prevent high voltage stresses in the transformer, each control winding is split into two or more windings, with the two windings being wound concentrically on their common core to reduce the voltage induced by the alternating current in the primary windings. In addition, the windings on the two auxiliary cores are cross-connected in pairs to equalize the reactance of each pair, thereby balancing the induced voltages. Finally, the transformer is physically constructed so that the start of the primary windings and the start of the control windings are at the same location so that the voltage difference between the finish of the control winding and the finish of the primary winding is subtractive rather than additive, thereby reducing the voltage stress imposed on the transformer insulation. Three variable reactance transformers constructed in accordance with the foregoing are connected in a three phase configuration with their primary windings being delta-connected. The control windings of each transformer are connected to corresponding varible control sources to further reduce the induction of high stress voltages in the control windings by the primary alternating current.

Parallel ac electrical system with differential protection immune to high current through faults

Abstract: In systems, such as aircraft electric power generation systems, three phase AC generators are often operated in parallel when supplying power to load busses and differential protection networks are utilized in each phase of each generator for detecting current imbalance between the phase conductor at the load and the neutral conductor of each phase. In this invention there is provided voltage limiter means such as back-to-back Zener diodes across each of the current transformers related to the phase and neutral conductors which, in conjunction with the other portions of the differential protection networks: (1) prevents nuisance tripping on the occurrence of high current faults outside the differential protection zone (such as bus faults) due to normal variations of the current transformers, and (2) at the same time, provides differential protection for a generator channel over the required range, generally from very low differential fault currents to the very high differential fault currents. The high differential fault currents will appear as high through current faults for the unfaulted parallel channels.

Signal loss detector for three phase circuit

Abstract: A three-phase rectifier utilizes three feedback controlled ferroresonant regulators to convert a three-phase signal into a regulated DC voltage. A monitoring circuit is included which responds to a signal loss at any input phase to actuate an alarm signal.

Ripple control systems

Abstract: A three phase ripple control system for feeding a control signal onto each phase line employs an injection transformer having a primary winding and three secondary windings. A control signal generator is connected in circuit with the primary winding and serves to provide a signal thereto. A respective inductor is connected in series in each phase line and is connected in parallel with a respective one of the secondary windings. The inductors have a value of inductance arranged such that their impedance at line frequency is substantially smaller than the magnetizing impedance of the transformer. The secondary winding thereby introduce a common control signal onto each of the three phase lines.

Dual voltage, dual battery charging system

Abstract: To provide for automatic charging of two batteries which are series connected, particularly to supply the on-board network of an automotive vehicle from a main battery and to supply additional higher surge voltage output to the vehicle starter, a three phase alternator has output rectifiers connected to two phases, and the rectifier to the main battery, the third phase with its rectifier being connected to the auxiliary battery. The third phase rectifier may, instead of diodes, include a diode-transistor combination, the transistor being controlled by voltage of the second battery to, selectively, charge the second battery or connect the third phase for charging of the main battery. The phase windings of the alternator may all be identical, the lighter loading of the phase connected to the additional battery providing the higher output voltage required thereby.

Diagnostic circuit for vehicle mounted three phase generators - uses waveform analysis circuits to locate faulty components

Abstract: A diagnostic circuit is for fault finding in the three phase generator systems of vehicles, which usually produce a direct voltage via suitable rectifier bridges, and uses automatic waveform analysis circuits to detect faulty components. Maintenance efficiency in such vehicles is improved, particularly when the generating equipment is relatively inaccessible. A typical vehicle generator consists of a three phase generator with star connected generating windings (4) feeding a six diode rectifying bridge (5, 6) to produce a direct voltage which charges the battery (7) and also drains a control circuit (10) which in turn feeds the generator field winding (2). Different speed voltage characteristics and output waveform shapes correspond to different faults in this network, and the output is analyzed. A number of different analysis circuits, including logic flipflops, bandpass filters, amplifiers and waveform squaring circuits are described. Essentially, these detect the various harmonic components in a faulty network and indicate corresponding faulty components.

Three phase unbalanced loading protection - involves making use of ripple components in rectified three phase current to produce unbalance current

Abstract: The output of three current transformers, one in each phase feeding the load, is applied to a rectifier bridge whose output in turn energises the overload relay. The unbalanced load protection makes use of the voltage developed by this bridge across a loading resistor. The bridge voltage is applied via an integrator and potential divider to one input of an operational amplifier, whilst the other input is connected to the unsmoothed bridge voltage. The amplifier, which is connected in different mode, then gives an output dependant upon the a.c. component of the bridge voltage. In the case of unbalanced load the a.c. component will increase, and a level detector can be made to operate a trip when a predetermined level is reached.

Unobtainable phase detection dircuit used in three phase power source

Abstract: A circuit for detection of a missing phase voltage condition, and certain other malfunction conditions, in the output of a three-phase A.C. alternator or power supply. Three pulse forming circuits are provided with their input ends each connected to receive a different one of the phase voltages. Each pulse forming circuit provides an output pulse signal for a duration corresponding to the excursion of its corresponding phase signal in a predetermined one of the voltage polarities of the power supply. The outputs of the pulse forming circuits are connected to individual inputs of an OR gate circuit. The OR circuit is adapted to clamp the trigger input of a retriggerable monostable multivibrator to ground during presence of a pulse output from any of the pulse forming circuits. The duration of a triggered output state of the multivibrator is chosen to be greater than the period of alternation of the phase voltages. A construction may be provided in which the pulse forming circuits and the input channels of the OR gate network are formed of opto-isolator units to achieve electrical isolation of the input and the output stages.

Digital electronic three=phase electricity meter - has pulse-width and amplitude modulators connected to each phase

Abstract: The three-phase electricity meter consists of resistive shunts placed in each phase which detect the load currents. Each shunt is connected to an amplifier whose output voltage is proportional to the load current in the respective phase. This voltage controls pulse-width modulators. The modulators control switches via opto-electronic couplers. The switches are thus operated by digital signals from the modulators. Amplitude modulators, comprising inverting amplifiers connected to each phase, deliver a current proportional to the prduct of phase voltage and phase current. These currents are fed to a common current-frequency converter whose output controls a stepping motor driving a counter mechanism.

Speed control for async. three phase motor - has two separate windings, one used for driving by three phase current

Abstract: The system may be used in passenger lifts. The first winding is used as the driving winding using the three phase supply. The other winding is used for braking the motor using d.c. Driving and braking effects are controlled by current control in accordance with control conditions. The nominal value for control varies in time, to give a programmed acceleration and deceleration curve. The acceleration increase is determined by a differential counter voltage in the reference element. The nominal voltage so produced continuously rises after the differentiation end at an adjustable slope until the maximum is reached.

Subharmonic oscillations in three-phase circuits

Abstract: This paper analyzes the subharmonic oscillations generated in three-phase circuits by the asymptotic method. As the result of the analysis, we find that there are three kinds of the 1 3 -harmonic oscillations, 1 3 -harmonic oscillation with beats, 1 3 -harmonic oscillation without beats and 1 3 -harmonic oscillation occurring in a single phase of the three-phase circuit. By means of an experimental circuit we confirm these oscillations.

Three-phase.two-phase power conversion transformer

Abstract: PURPOSE: TO provide a minimum level of neutral point current with respect to a singlephase side load, by a constitution of secondary winding being composed of a doubledelta-connection, with its any one phase connected in parallel, and boosting deltaconnections, connected in series to the above said parallel connected phase line. COPYRIGHT: (C)1979,JPO&Japio

Universal welding current supply - with additional charge-discharge circuit and power thyristor on supplementary electrode

Abstract: The supply for connection to a single phase or to a three phase mains is equipped with an additional charge and discharge circuit which includes a capacitor, a charge and a discharge thyristor. An additional power thyristor to produce current pulses of positive polarity has its cathode connected to the junction of discharge thyristor and an induction coil, and its anode through a switch to the mains. Suitable for welding ferrous, non-ferrous, and light metal alloys. The current supply unit has small weight and overall dimensions and can be connected to either single phase or three phase mains.

Power supply for electronic recorder electricity meter - has 3 phase rectifiers with 2 protective resistors in series and common charging capacitor

Abstract: Power supply is for electronic recorder of energy consumption or electricity meter with or without additional devices in polyphase energy networks. The AC voltage of the single phases (R, S, T) is rectified by three phase rectifiers (D1, D2, D3) with two protective resistors in series for each phase connection against excess voltages. A common charging capacitor (C) is assigned to each rectifier arrangement. Capacitors and voltage dependent two poles for interference suppression are switched from the connecting points of the protective resistors to the neutral conductor (M). In networks without a neutral conductor (M), the latter is artificially produced.

Hybrid simulation of fuel cell power conversion systems

Abstract: Simulation techniques and results are presented for hybrid computer studies of line-commutated and self-commutated three phase bridge inverters. The line-commutated bridge system included constant extinction angle control of the inverter, power regulation of the DC source, and power factor correction capacitors. Simulation of this system was performed in real-time which allowed testing of prototype control hardware. The self-commutated system consists of three bridges operating in a phased sequence which permits elimination of harmonics by cancellation. System performance is evaluated with the inverters operating into a three phase load, part of which is supplied by the utility system. The paper discusses the computational techniques used in simulating systems of this type, including the role of the digital and analog computers in each study. This work supports the conclusion that hybrid simulation is a valuable tool for analysis and evaluation of power conversion systems which contain current switching devices.

Airborne pulse magnetron and power supply system

Abstract: The power supply for an airborne pulse radar includes an unfiltered source of 400 cycle AC power connected to a full wave rectifying circuit including two diodes associated with each phase of the three phase input circuit. In addition, three SCR's are employed for controlling the operation of the rectifiers. During normal operation of the pulse magnetron power supply, the control electrodes of the SCR's are biased to the conducting or enabled state by a small floating DC voltage which is obtained from a small DC power source which includes a rectifier circuit connected to the floating secondary of a low voltage transformer. When a fault is sensed in the magnetron pulse circuitry as indicated by the drawing of excessive current, a switching circuit is activated which removes the enabling voltage across the SCR's, so that the input rectifier circuitry is disabled, thus preventing burn-out of components included in the pulse generation circuitry.

Electronic relay for balanced loading of three=phase network - uses phase load current to control duty factor of multivibrator

Abstract: The electronic 3-phase relay, for balanced loading of a 3-phase network, has a shunt (1) in one phase (R). This shunt is used to obtain a voltage proportional to the load current in this phase. This proportional voltage is amplified and used to control the duty factor of an astable multivibrator (8). The duty factor switches a voltage (U1, U2) proportional to the geometric sum of the two other phase voltages, with respect to the phase being considered. A summation amplifier adds the voltages.

Electronic three phase electricity meter - uses variables proportional to phase powers which are converted into pulses applied to counter

Abstract: Load current flowing in each phase line is converted by a shunt in a variable proportional to it. A variable proportional to the phase voltage is derived from it through a resistor. The two variables are applied to a multiplier and a quantising device. Pulses delivered at the quantiser output are applied to a counter. Pulse trains at the quantiser (32-34) output, proportional to the phase powers, are applied to a common counter (42) through a synchronisation device (35-37) and an electric decoupling device (38-40). Each phase (R, S, T) has a transformerless coupling (46-48) to the neutral line (0) of the three-phase supply.

Three:phase supply monitor circuit - phases connected to resistive divider and diode rectifier for simultaneous detection of voltage, symmetry and phase succession

Abstract: The three-phase AC supply monitor circuit simultaneously detects voltage, symmetry and phase relationship. The three phases are connected to a resistive divider and diode rectifier. A voltage-follower transistor fed from the rectifier, charges a capacitor. If the voltage of all three phases is the same, current pulses of equal amplitude appear at the output of a second transistor. No pulse is produced if the voltage falls below a set value. An integration-type circuit gives an output proportional to the number of pulses and operates a relay if the voltage equals that set by a reference circuit. If the phases are out of step, a detector circuit causes a transistor to conduct, thus discharging the capacitor and preventing the relay from operating.

Rotation speed control apparatus for three phase induction motors

Abstract: PURPOSE:To effect rotation speed control for a three phase induction motor by controlling only one line of the three phases.

Three phase quasiirectangular vscf induction generator system

Abstract: A plural switch matrix is connected as a direct ac-to-dc converter between an induction generator and an a-c load. The generator provides three-phase output energy which is switched and controlled by the converter, to supply a controlled three-phase quasi-square wave (QSW) voltage to a load. The converter switching provides periodic shorts across the generator terminals, translating some of the mechanical input energy into electrical energy to sustain the generator field. The converter is regulated by gating signals from a combinational logic circuit.

Multiple point HV DC transmission system - has several rectifier annaand inverter stations connected in series by ring line

Abstract: A multiple point high voltage d.c. transmission system has rectifiers and inverters connected with three phase networks. Current and/or voltage controllers and a signalling device are allocated to these rectifier and inverter stations. A d.c. two-wire line interconnects all stations. Each station has switches in both d.c. wires, and a transverse link with switches between the wires. Each station has a shunting switch in a connecting wire between the transverse links.

Three-phase AC voltage monitoring circuit - checks deviations from amplitude tolerance limits and generates DC voltage

Abstract: The circuit generate a d.c. voltage compared with a six-pulse rectified three-phase a.c. voltage. The reference voltage is a pulsating d.c. voltage whose peak values lie within the tolerance limits of the six-phase rectified a.c. voltage, and shape sufficiently simulates it. It is generated by the circuit from a constant d.c. voltage and a superposed trapezoidal pulsating d.c. voltage. The circuit arrangement comprises a transformer with a primary coil (31R, 31S, 31T) between one of the phase lines and neutral (mp) and the secondary connected with a bridge circuit which has a resistor (33) connected across the diagonal of the bridge. Each diagonal has also a diode (34), and a Zener diode (35) is in the common line connection to the three bridge lines.

Transient behaviour of a static compensator with ferromagnetic non-linearity

Abstract: Static compensators using saturable reactors and capacitors are frequently used in power transmission systems for voltage stability and reactive power control. To be able to determine the behaviour of the compensator on-line computer programs has been developed which models the three phase, double zig-zag connected saturable reactor including the six magnetic cores. The iron and copper are properly taken into account to provide the right damping effect. The program determines the instantaneous behaviour, for instance the phase currents and the inductive field versus time. Steady state results are used to determine the overall voltage versus current and the harmonic content of the current. Transient behaviour are also computed. Agreement between theory and experiment on a 55 MVA/12 kV prototype is excellent. So far our program is able to simulate correctly the internal behaviour of the compensator and its influence on the line as well in steady state as in transients. This elaborate analysis can be further used to define simpler and less expensive tools more suitable for every day use.