Showing papers on "Power factor published in 1968"

Human power output.

Abstract: IT has been known for a long time that power output in man increases rapidly with decreasing duration of exercise, but there have been few systematic studies of this problem. Indeed, measurements of the power output of the body during a single movement lasting one-tenth of a second or less have not been made.

Influence of Excitation and Speed Control Parameters in Stabilizing Intersystem Oscillations

Abstract: Intersystem power oscillations have occurred between the interconnected utility systems of Saskatchewan, Manitoba, and Ontario (West System). Such power swings have been most evident when the power transmission angles on the interconnections or on certain internal 138-kV and 115-kV transmission have been of relatively great magnitude. The oscillations have been controlled or reduced by adjustment of the excitation of speed control parameters on various groups of machines throughout the three inter- connected systems. The analytical techniques utilized to determine the adjustments will be of considerable benefit in planning future exrtensions to the interconnections and facilities within the power systems in the three provinces.

Four Methods of Power System Damping

Abstract: Techniques for damping power system swings have been studied by analog and digital simulation.

High frequency power supply

Abstract: A static, single-phase, alternating current supply for powering an inductive load In a preferred embodiment, the load is an induction heating coil with parallel power factor correcting capacitors, but equivalent elements consisting of parallel connected inductance and capacitance may be incorporated in the system and any external load can then be powered Adjustment of output power and/or voltage is accomplished by varying the frequency of the supply The preferred embodiment includes an alternating current input of line voltage and frequency, a rectifier producing DC output voltage of substantially constant magnitude, an inverter capable of operation over a range of frequencies for converting the DC voltage to high frequency alternating current, and inductive reactance between the inverter and the load The frequency of the inverter is controlled by an oscillator which has various inputs providing control functions

Telemetry circuit for an ac power system

Abstract: This disclosure deals with an electric system including an alternating current power supply, at least a pair of power lines adapted to connect the power supply to a load, a pulse transmitter connected across the power lines, and a pulse detector connected to the power lines. The pulse transmitter includes a potential breakdown device and a potential storage device. As the AC potential across the two power lines, which is also the potential across the transmitter, changes, the breakdown device responds to the instantaneous potential drop across the power lines and fires. Either charging or discharging current then flows through the breakdown device and the storage device, such current flow resulting in a pulse appearing on the two power lines. This pulse is picked up by the detector.

A Transformer-Ratio-Arm Bridge for Measuring Large Capacitors Above 100 Volts

Abstract: A high-voltage bridge suitable for measuring capacitance ratios up to a million to one is described. The high ratio is realized by cascading a two-stage current transformer to a bridge based on the current comparator principle. Circuits that compensate for the lead impedances of large capacitors are presented. The bridge is direct reading in the capacitance ratio and the dissipation factor and the uncertainties for both components are less than 10 parts per million (ppm).

A New Method of Determining Loss Coefficients

Abstract: A new method is presented for finding B coefficients expressing loss in a power system as a function of power input. The computer program necessary to find these loss (B) coefficients is very simple, and transformations of variables are not required. The method takes advantage of the fact that partial derivatives of voltage phase angles with respect to any plant power output are independent of system generation schedules and load levels, as shown in a previous paper. Many of the usual assumptions in calculating B coefficients are eliminated.

Shunt regulation electric power system

Abstract: A regulated electric power system having load and return bus lines. A plurality of solar cells interconnected in power supplying relationship and having a power shunt tap point electrically spaced from the bus lines is provided. A power dissipator is connected to the shunt tap point and provides for a controllable dissipation of excess energy supplied by the solar cells. A dissipation driver is coupled to the power dissipator and controls its conductance and dissipation and is also connected to the solar cells in a power taping relationship to derive operating power therefrom. An error signal generator is coupled to the load bus and to a reference signal generator to provide an error output signal which is representative of the difference between the electric parameters existing at the load bus and the reference signal generator. An error amplifier is coupled to the error signal generator and the dissipation driver to provide the driver with controlling signals.

Redesign of DC Motors for Applications with Thyristor Power Supplies

Abstract: The accelerated trend toward the use of solid-state controlled power conversion equipment, as a replacement for the conventional Ward-Leonard motor generator set in direct current adjustable speed industrial drive systems, has focused attention on a number of undesirable side effects which detract from their outstanding advantages. These effects are due to the high ripple content in the rectified voltage output of the conversion units, which ' causes increased heat generation in the dc drive motor and adversely affects its ability to commutate armature currents without sparking at the brushes. These effects are described and analyzed for several basic configurations of converter power circuits. The use of a laminated steel frame motor construction instead of the conventional solid steel frame ring to miniimize these effects is discussed.

New Aspects of Power Factor Improvement Part II---Practical Circuits

Abstract: This paper brings forward and analyzes the practical power-electronic circuits One of the more interesting configurations described is an inductive element in which, due to constrained reactive power flow, capacitive properties are achieved with regard to the supply network

A Thyristor Alternating-Voltage Regulator

Abstract: The control of thyristors used in alternating-voltage regulators employing synchronous tap changing is normally complicated when there are wide variations in load power factor. The modified form of tap changing circuit described here simplifies these control problems and because of the different operating mode produces less distortion in the output waveform. The essential feature of this circuit is that a tapped inductor carrying a controlled direct current is connected in the output circuit of the regulator. This inductor prevents tap-to-tap short circuits and effectively provides an additional output voltage level.

Brushless and self-excited 3-phase synchronous machine

Abstract: The paper describes a brushless and self-excited synchronous machine, which uses current compounding in auxiliary stator and rotor windings to produce an excitation current which increases as the load current is increased. With the machine used as an isolated alternator, the effect is sensitive to the power factor of the load, and the increase in excitation current is greater as the load becomes more inductive. The constancy with which the terminal voltage of an experimental machine is controlled as the load varies is comparable with that obtained with typical static current-compounded excitation schemes, and a feature of the new scheme is the very rapid recovery of the terminal voltage following a sudden increase in load. As with static schemes, the new system is readily adapted to control either the power factor or the reactive power of the input to the machine, operated as a synchronous motor on an infinite busbar. Results obtained from the experimental machine again indicate an accurate control, from no load to well beyond full load.

Frequency-dependent dynamic, representation of induction-motor loads

Abstract: For comprehensive transient and dynamic stability studies, induction-motor loads have usually been represented by fixed shunt impedances at system nominal frequency. A method is proposed here which allows single induction motors or groups of induction motors to be considered as frequency-dependent and dynamic. If the necessary parameters of the motors are known and if computation effort is not a problem, accurate assessment can always be made for single machines or groups of machines but may involve lengthy calculations. Alternatively, an approximate, rapid method is presented which gives the change in active-power input to an induction motor or group of induction motors due to inertia and frequency-variation effects to within ±2% of the actual change for known power factor, inertia factor and full-load slip; and to within ±5% of the actual change when the assumed parameters are within the following limits: power factor within ±5% inertia factor within ±10% and full-load slip within ±20% (where the actual change in power has been assessed by the use of an equivalent circuit). The change in reactive power, as assessed, is within ±20% of actual change in reactive power. ±5% change in operating frequency has been considered. For simplicity, windage and friction losses have been taken as an integral part of the load supplied by the motor, and core losses have been assumed constant. These methods can be applied to power-system stability studies, as illustrated by an example.

Line voltage compensating pulsed power welding supply

Abstract: THE PULSED POWER WELDING PROCESS IS IMPROVED BY USING SHORTER ARC LENGTHS, WHICH BRING A NEED FOR HOLDING THE ARC VOLTAGE SUBSTANTIALLY CONSTANT. TO DO THIS, LINE VOLTAGE COMPENSATION IS REQUIRED. IT IS ACCOMPLISHED IN A PULSED POWER WELDING SUPPLY BY A FEEDBACK LOOP WHICH CONTROLS THE PORTION OF THE CYCLE DURING WHICH CURRENT IS PASSED THROUGH A TRIGGER RECTIFIER, WHICH TRIGGER RECTIFIER IS NOT COUPLED TO THE LOAD CIRCUIT. THE TRIGGER RECTIFIER CONTROLS THE PASSASGE OF POWER THROUGH A HEAVY DUTY, POWER-TYPE RECTIFIER WHICH IS ENERGIZED DURING PERIODS OF WELDING. THE FEEDBACK LOOP IS ALLOWED TO REACH A STEADY STATE BEFORE POWER IS FIRST APPLIED TO THE POWER RECTIFIER, WITH THE RESULT THAT TRANSIENTS IN THE POWER RECTIFIER LOAD ARE AVOIDED. IN THE LOOP, A COMPARISON IS MADE BETWEEN A MANUALLY CONTROLLABLE REFERENCE WAVE AND A SAMPLE WAVE DERIVED FROM THE OUTPUT OF THE TRIGGER RECTIFIER. LINE VOLTAGE VARIATIONS ARE COMPENSATED BY CHANGES IN THE LENGTH OF THE PORTION OF THE CYCLE DURING WHICH THE TRIGGER RECTIFIER IS CONDUCTING.

Thermal analogue protection for capacitors

Abstract: A capacitor protection system is provided having the primary winding of a potential transformer connected across a series capacitor bank to be protected and the secondary winding of the potential transformer connected to a thermal analogue device which reproduces the thermal characteristics of the capacitor and operates capacitor switching means when dangerous thermal conditions are reached. An inverse time voltage relay is also connected across the secondary winding to initiate protective capacitor switching responsive to high current faults. The thermal analogue device simulates the internal thermal conditions of the capacitor based on the principle that the power loss in the capacitor is proportional to the square of the voltage across the capacitor. Voltage comparison circuits are also provided between groups of capacitors in banks having multiple groups to detect blown fuses associated with respective capacitor groups.

High current square wave power source

Abstract: A SQUARE WAVE POWER SUPPLY USED IN PRESSURE SEAM WELDING OF AN BODIES. PHOTOELECTRIC CELLS DETECT THE PRESENCE AND LOCATION OF CAN BODIES PASSING BETWEEN PRESSURE ROLLER ELECTRODES TO ACTUATE SOLID STATE SWITCHES. A THREE PHASE A.C. SOURCE IS RECTIFIED AND FILTERED TO PRODUCE A SOURCE OF DIRECT CURRENT. AN OUTPUT TRANSFORMER AND A FIRST SCR ARE CONNECTED IN SERIES ACROSS THE DIRECT CURRENT SOURCE. CONNECTION OF THE OUTPUT TRANSFORMER WITH THE DIRECT CURRENT SOURCE IS CONTROLLED BY TWO TIMING CIRCUITS, ONE OF WHICH CONTROLS THE CONDUCTION DURATION OF THE FIRST SCR AND THE SECOND OF WHICH CONTROLS THE BLOCKING DURATION OF THE SCR. CONDUCTION OF THE SCR IS TERMINATED BY A POSITIVE QUENCHING THEREOF THROUGH THE APPLICATION OF A VOLTAGE ACROSS THE SCR GREATER THAN AND IN OPPOSITION TO THE VOLTAGE OUTPUT FROM THE DIRECT CURRENT SOURCE. A SUBSTANTIALLY WELL DEFINED AND CONSISTENT SQUARE WAVE OUTPUT IS PROVIDED BY PULSE-SHAPING CIRCUIT ELEMENTS IN COOPERATION WITH THE OUTPUT TRANSFORMER AND SCR AND BY ESTABLISHMENT OF A PRELIMINARY FLUX LEVEL IN THE OUTPUT TRANSFORMER PRIOR TO THE INITIATION OF AND UPON TERMINATION OF A TRAIN OF SQUARE WAVE OUTPUT CURRENT SIGNALS. AN OVERLOAD TIMING CIRCUIT PROTECTS THE SUPPLY BY TERMINATING THE INPUT THERETO.

Steady-State Performance and Analysis of the Series Resistance--Capacitance Circuit with Control by Adjustable Thyristor Triggering

Abstract: A pair of thyristors connected inverse parallel, with symmetrical triggering, are found to give smooth, stepless control of the current and load voltage in a series resistance-capacitance circuit. Large current pulses of adjustable amplitude are produced that appear to be suitable for electric welding. The application to power factor compensation of inductive loads is limited in usefulness due to poor waveform and high dissipation in the resistance-capacitance branch.

Two State Modulation Techniques for Power Systems.

Abstract: : This is the fourth semi-annual report on an investigation of techniques and circuitry based on the use of two-state modulation systems, directed toward development of improved advanced power conditioning equipment. Improvements are sought with respect to smaller, lighter weight, more efficient and highly reliable power processing systems. During this reporting period, two experimental power processors were designed, constructed, and tested.

Analog Computer Study of Automatic Frequency Ratio Control on an HVDC Transmission System

Abstract: A method has been developed to simulate an automatic frequency control system in ac-dc power transmission on an analog computer. As an example of an ac-dc system a model of Sakuma frequency changer, between Tokyo Electric Power Co. system (50 Hz) and Chubu Electric Power Co. system (60 Hz), is studied in detail. Three new methods of automatic frequency ratio control (AFRC) by dc transmission are considered and compared. The variation of frequencies in the ac systems and the dc power change due to a step load increase in the Chubu power system are examined. These frequency variations and power change are used to optimize the parameters of the AFRC devices.

Current Regulators for Large Rectifier Power Supplies Used on Electrochemical Processing Lines

Abstract: Typical large silicon rectifier dc power supplies for electrochemical lines have ratings of 20 000 to over 300 000 amperes, at voltages of 50 to 1000 volts. The operating efficiency of such installations is of major economic importance, and experience has shown that the use of high-accuracy current regulation can substantially improve efficiency. Regulation is required to compensate for ac supply fluctuations and electrochemical cell or potline characteristics variations. Underload tap changing transformers provide an economical and highly efficient means of varying the rectifier dc output voltage. Control resolution, however, is relatively limited due to the finite voltage steps between taps, and precautions must generally be taken to avoid unnecessary tap changer operations in order to achieve reasonable operating periods without contact maintenance. Several techniques for achieving high-accuracy current regulation with tap changer controlled silicon rectifier power supplies are described. One approach utilizes partial range saturable reactors to provide vernier control between tap changer steps and a fast response feedback amplifier-driver to give essentially continuous high-accuracy (0.1 to 0.5 percent) current regulation. Another method controls the tap changer by means of an error integrating or reset amplifier technique which ignores minor short-tenn current fluctuations but maintains the average value over several hours of operation to within a fraction of a percent of the preset value.

Electrical circuit with power inlet control

Abstract: This disclosure relates to a primary circuit supplied with electrical power by a power inlet and an auxiliary circuit controlled by the power inlet. The power inlet carries an auxiliary circuit controlling switch which is actuated by the connecting and disconnecting of the power inlet with a mating electrical connector device to complete the primary circuit.

Hierarchical Control of a Multimachine Power System Model

Abstract: The power-frequency control of a multimachine power system model is investigated using combined boiler-turboalternator units interconnected with the general node equations of a transmission network. The boilers, represented by lumped energy storage elements, are combined with the turbine equations using flow- power relations associated with static operating characteristics. The alternators are represented by a linearized set of Park's equations in a form suitable for investigating the effects of voltage regulator action.

Basic Principles of Planning VAR Control on the American Electric Power System

Abstract: The broad principles are described which are used in the planning of VAR supply and control on the American Electric Power System. The discussion relates to the selection, utilization, and coordination of various VAR supply and control equipment, such as generators, synchronous condensers, static capacitors, and shunt reactors. Emphasis is placed on the importance of a well planned and coordinated VAR control in the design of a reliable power system.

Instrumentation for Thyristor Control

Abstract: Since thyristor control produces nonsinusoidal periodic waveforms with high harmonic content, the electrical measurements associated with such controls require some adaptation of the existing techniques which have evolved mainly for the measurement of constant (dc) or sinusoidally varying (ac) electrical quantities. The basic principles and instruments discussed are relevant to voltage, current, real and reactive power, and power factor measurement in situations most likely to be encountered in applications of silicon-controlled rectifiers (thyristors).