Showing papers on "Power factor published in 1976"

Reactive Compensation and Harmonic Suppression for Industrial Power Systems Using Thyristor Converters

Abstract: This paper discusses the problems and solutions of applying reactive compensation, either static or dynamic, to industrial power systems supplying large blocks of dc power from diode or thyristor converters. The resonance between power capacitors and system reactance can produce high harmonic voltages caused by the harmonic currents generated by converters. The interaction between these harmonic voltages and regulating systems can be minimized by the use of suitable filters. The design of these filters should eliminate the interaction between power system and load and reduce harmonic current flow. Different methods of reactive power control are also discussed.

Reactive power generation and control by thyristor circuits

Abstract: Generally, static VAr generators function as variable reactances (capacitive or inductive impedances) or controllable ac current and voltage sources. This paper reviews possible methods of VAr generation and control by static thyristor circuits and describes new approaches in which power frequency changers (cycloconverters) are employed. Oscillographic recordings illustrate the operation and performance of practical systems, including a 35 MVAR arc furnace compensator.

Power factor control system for AC induction motors

Abstract: A power factor control system for use with AC induction motors which samples line voltage and current through the motor and decreases power input to the motor proportional to the detected phase displacement between current and voltage to thereby provide less power to the motor, as it is less loaded.

Power supply circuit for camera

Abstract: A power supply circuit for a camera wherein a detection circuit which detects the voltage of a power source is provided for supplying an electric power to the electric circuit of the camera only when the detected voltage is above a preset value.In the power supply circuit, the power supply is controlled by a detection output obtained after a voltage detecting action is performed in a stable condition by the detection circuit. The power source voltage is detected in a manner suitable for the characteristic of the battery employed. Further, the voltage detection is performed only momentarily to prevent unnecessary power consumption for voltage detection.

Energy demand controller and method therefor

Abstract: An energy demand controller having a sensor for measuring the instantaneous power being delivered to a building, a thumb wheel switch for preselecting a power limit for use in the building, and circuitry for comparing the instantaneous power to the power limit and to switch off power to various heating zones within the building in order to maintain the instantaneous power below the preselected power limit. The control circuitry includes a cycling circuit only operative when the instantaneous power exceeds the measured power to deactivate a sufficient number of heater circuits in order to drop the instantaneous power below the preselected power limit for a predetermined time interval only. At the end of the predetermined time period, the deactivated heater circuits are turned back on. If the instantaneous power still exceeds the preselected power limit, then other zone heaters of sufficient number are likewise deactivated in a second predetermined time interval. As long as the instantaneous power exceeds the preselected power limit when the predetermined time intervals terminate, the heater circuits, in similar fashion, will be cyclically turned off and on so that heat loss in any given area is minimized. When all heater circuits within the predetermined time interval are deactivated, and the instantaneous power still exceeds the power limit, then the hot water heater is deactivated. If the instantaneous power still exceeds the preselected power limit, an alarm will then sound to inform the inhabitant of the building to either increase the preselected power limit or to deactivate other electrical circuits within the building.

A fast decoupled static state-estimator for electric power systems

Abstract: A new algorithm is described to solve the static, time-invariant weighted least-square state-estimation problem for large-scale electric power systems. The solution is obtained through P-θ and Q-V decoupling and alternately iterating the active and reactive equations using fixed, simplified submatrices of the information matrix. Thus, a much faster algorithm is obtained yielding the exact solution and requiring little computer storage. The new method is compared with the basic "Weighted-least-square" and the "Line-Only" algorithms on a practical HV network.

Harmonic reduction in thyristor converters by harmonic current injection

Abstract: The paper describes analytical and experimental results for a new method of current harmonic reduction in thyristor converters. The principle of the method is to modify the current waveforms on the d.c. windings of the converter transformer by injecting harmonic currents at a particular frequency. In practice, third harmonic currents of the power frequency is most efficient. Experimental results carried out prove that the method is effective in reducing the alternating-current harmonics, and that it is applicable to any type of thyristor converters.

RF Impedance of United States and European Power Lines

Abstract: Impedance measurements were made of 86 commercial 50-Hz AC power distribution systems throughout the LF-HF (0.02-30 MHz) spectrum in six European countries. The impedances are those presented to devices/appliances connected to the ac power source. The European results are presented in graphic and tabular form and are compared to impedances of U.S. power lines.

Three-Phase AC Power Control Using Power Transistors

Abstract: A three-phase ac power control circuit using power transistors which operate in a high-frequency chopping mode is described. The circuit is capable of handling several kilowatts of power at any lagging load power factor angle and the output voltage can be smoothly controlled from zero to full supply voltage. The circuit has inherently fast response and the high-frequency ripple at the output is easily filtered. The development, study, and experimental evaluation of the circuit with resistive and induction motor loads is described.

A Closed-Loop Control System for the Reduction of Reactive Power Required by Electronic Converters

Abstract: A closed-loop control system to reduce the reactive power required by electronic converters is proposed. The instantaneous reactive power which consists of both displacement of fundamental current and harmonic distortion current is measured and compensated by a reactive power source connected parallel between the power lines and the converter. A combination of a dc choke and a forced-commutated inverter is used for the reactive power source.

A Controllable Secondary Multikilowatt DC Current Source With Constant Maximum Power Factor in its Three-Phase Supply Line

Abstract: A type of industrial size dc converter for submegawatt applications is described and illustrated with the characteristics of a small scale 10 kW model. High conversion efficiency near 97 percent is maintained at full power and with an internal frequency of operation near 10 kHz. The system is characterized by the behavior of a true current source with inherent short circuit capability of its output terminals. All power is processed via a firmly controlled high Q series resonant circuit. Feasibility of power densities in excess of 1 kW/kg component weight is demonstrated. This high power density reflects itself in low quantities of material needed for construction of these systems. Operation of the dc converter as part of a rectifier-filter converter system, powered from a three-phase supply line is described. Test data demonstrate a high power factor PF?0.95 for all conditions of converter loading. Data obtained from a thyristor bridge-filter system are presented and subjected to comparative analysis.

Parallel redundant and load sharing regulated AC system

Abstract: An electrical power system is provided having two power sources, one being a commercial power source and the other being an inverter. Both power sources are connected to the load so as to share the load, approximately equally. A voltage regulator is in series with the commercial power source, and the inverter is synchronized to the commercial power source. Means are provided for failure sensing and isolation of the inverter; and means are associated with the voltage regulator which is connected in series with the commercial power source to block and sense reverse power flow in a direction from the load towards the first power source and to initiate isolation of the first power source from the load when reverse power flow is sensed. Means may also be provided for sensing line quality parameters, particularly voltage, current and frequency of the commercial power source and for isolating it if any such sensed quality is outside of predetermined limits, so that the regulated inverter would be required to assume the load. On the other hand, if the inverter fails the commercial power line assumes the whole load, of which it already has approximately half, so that the system becomes line redundant. The invention may also be applicable to parallel operated line-regulated AC lines each deriving power from independent commercial AC sources.

A simplified approach to determination of saturated synchronous reactances of large turbogenerators under load

Abstract: This paper details the use of computerized magnetic field solutions, based on magnetic vector potential, to develop a simplified approach to the calculation of saturated values of steady state reactances of turbogenerators under various load conditions. When magnetic nonlinearity of the stator and rotor materials is taken into account, the turbogenerator reactances become dependent on the saturation conditions in the machine, which are a function of the operating conditions (terminal voltage, current and power factor). Quadrature axis synchronous reactances are reduced by as much as 40% from their classical unsaturated values under rated load. Torque angles deduced from the model at rated load are lower by as much as 20% than values obtained by standard methods. The method is applied to two typical 4-pole, 659 MVA and 2-pole, 733 MVA turbogenerators of the gas inner-coaled type. Supportive shop floor test results are provided.

Frequency controlled induction cooking apparatus

Abstract: The invention relates to induction heating for cooking. Solid state reciprocal power switches are used to excite a resonant power output circuit including an induction coil to be inductively coupled to a cooking utensil. A first control signal which is a function of the Q of the coil, the direct current voltage applied to the power switches and the frequency of operation of the power switches is used to offset the power circuit from oscillating at resonance in order to control the power output. A solid state differential circuit is used responsive to a second control signal establishing the level of power desired and to the first control signal for regulation about the selected power level. The same differential circuit is responsive to a third control signal to insure low starting power or in case of a failure of the power line. Minimum power output is provided at the lower end of the ultrasonic frequency spectrum without entering the audible frequency range.

Static shunt compensation for voltage flicker reduction and power factor correction

Abstract: It is shown that a static VAR generator comprising a capacitive filter network and a thyristor-controlled inductor can effectively compensate for rapid and unbalanced load variations and is able to maintain system voltage and power factor, even under extremely adverse load conditions. The performance of such a static compensating system is, however, dependent on the principles of control employed, the adequacy of the VAR rating, and the electrical characteristics of the filter network. In arc furnace applications, the VAR generator must be rated for unbalanced load conditions and the capacitive filter network must be designed to be compatible with the ac system impedance, and with the spectrum of the furnace current that contains both odd and even harmonics.

Power supplier for magnetron

Abstract: The present disclosure relates to a power supplier for a magnetron for use in electric appliances, such as a microwave oven. The power supplier of the present disclosure has a solid state frequency converter which changes commercial A.C. power to A.C. power at a high frequency, which A.C. power is increased in voltage in a step-up transformer and then fed to the magnetron. The power supplier further has a control system which stabilizes the power to be applied to the magnetron with respect to a preselected reference level and a power supplier protecting circuit for protecting the power supplier from an unexpected low voltage occurring in the commercial power source.

Multiple output self oscillating converter regulator power supply

Abstract: A multiple output switching regulator power supply operates as a self-oscillating circuit with a light weight ferrite core transformer and a sense winding used exclusively for voltage regulation purposes. A power transistor switch is employed to selectively connect the transformer primary across a DC source of power to provide energy storage when the switch is closed and to provide energy transfer when the switch is open, by way of transformer flyback. The power transistor switch is controlled by a feedback circuit which includes a current sink connected to selectively divert current away from the base of the power transistor switch and a timing circuit for controlling the operation of the current sink. A capacitor, connected across the sense winding is monitored by a high gain voltage comparison circuit which activates the timing circuit in dependence on the voltage variation on the capacitor.

Aircraft electrical systems

Abstract: Preface 1. Direct Current Power Supplies 2. Alternating Current Power Supplies 3. Power Conversion Equipment 4. External and Auxiliary Power supplies 5. Power Distribution 6. Circuit Controlling Devices 7. Circuit Protection Devices and Systems 8. Measuring Instruments and Warning Indication Systems 9. Power Utilization - Motors 10. Power Utilization - Systems 11. Electrical Diagrams and Identification Schemes Appendices 1. Electrical and Magnetic Quantities, Definitions and Units 2. Ohm's Law 3. Power in A.C. Circuits 4. Connection of Capacitors and Inductors 5. Fundamental A.C. Circuits and Formulae 6. Conversion Factors 7. Power Generation System Applications 8. Electrical Diagram Symbols 9. Representative Aircraft Ice and Rain Protection Systems 10. Abbreviations and Acronyms associated with Electrical Systems. 11. Logic Gates and Truth Tables Exercises Solutions to Exercises Index

Current fed inverter with commutation independent of load inductance

Abstract: A three phase bridge inverter supplies rectangular wave currents to an inductive load and to capacitors connected in wye across the load for wave shaping as well as filtering and power factor correction. A commutating capacitor connected to the midpoint of the wye-connected capacitors is controlled by two auxiliary thyristors. The commutating capacitor voltage is sensed and an incoming thyristor is not fired until the voltage rises to a level sufficient to commutate the next thyristor in sequence. This commutation is independent of load inductance.

Line power distortion detector

Abstract: Apparatus for testing distortion of an AC power wave and providing an error signal if distortion of the type likely to cause DC output of a power supply receiving the AC power wave to fall below acceptable levels occurs.

Correction system for regulating the power factor of an electrical network

Abstract: A correction system for regulating the power factor of an electrical distribution network in which the phase difference between the potential V and the current I of a distribution line is measured. The voltage V and current I are detected, the phase difference between V and I measured, and the measured phase difference compared with first and second predetermined reference limits. When the measured phase difference is less than a first predetermined reference limit, capacitive loads may be added to the network, and when the phase difference exceeds a second reference limit greater than the first limit, the capacitive loads may be disconnected from the network. The actual demand is monitored and the capacitive loads connected only when the actual demand exceeds a predetermined demand value.

A computer study of battery energy storage and power conversion equipment operation

Abstract: This paper presents and discusses results from a computer simulation of a battery energy storage/converter system connected to a representative utility substation. Switching of load, voltage waveforms, voltage levels, fault conditions, and power flow reversal are investigated for both line- and forced-cornmutated converters in the application. The interactions among the battery, the converter and its controls, and the substation are discussed. The investigations have pointed out areas in which further consideration must be given to component selection for the battery/utility interface equipment, for example, dc reactor sizing, harmonic filtering, power factor control, thyristor firing control, and dc current interruption.

Amplitude stabilized power amplifier

Abstract: An amplitude stabilized power amplifier having a power splitter for dividing the power of an input signal into a predetermined number of channels, a plurality of amplifier modules for amplifying the power of each of the channels divided by the power splitter, and a power combiner for combining the amplified power signals to provide an amplified output signal. One of the channels of the power splitter is provided with a voltage controlled phase shifter whose phase shift is controlled by an operational amplifier which is responsive to a reference voltage and to the amplified output signal of the power combiner such that the signal in the channel provided with the phase shifter operates to limit the efficiency of the power combiner to maintain a power combiner output signal of constant power with respect to the reference voltage.

High speed-high voltage switching with low power consumption

Abstract: A capacitive load is charged through a series transistor. Peak charge currents for the load are drawn from a capacitive source whose charge is constantly maintained. Rapid discharge of the capacitive load is through a semiconductor diode and a cascade of transistors which act as switching elements. Diodes across the base-emitter junction of these switching diodes provide protection against transient damage as well as reducing the time required to cut-off conduction of the transistors. A simple transistor TTL drive (+5v) operates the switch.

Power circuit for induction heating

Abstract: A power circuit for use in billet heating, surface heat treating and melting and protective circuitry associated therewith. The power circuit generally comprises a source of potential in series with a pair of inductances and an inverter module. The inverter module has two sections each comprised of a thyristor in parallel with a diode. A pair of series connected charging capacitors are connected across the source of potential and a load is connected from between the capacitors to between the two sections of the inverter module. Current flows through one thyristor, through the load and charges the capacitors. The capacitors discharge and a reverse current flows through the load and through the corresponding diode. This cycle is repeated then with the opposite section of the inverter module. A commutation failure protection circuit is provided which detects the voltage collapse condition accompanying a short circuit through the inverter module and when this occurs, it acts to shut off the thyristors. An open load detect circuit is provided which senses the voltage build up which occurs when the load is open, and this circuit also acts to shut off the thyristors should this happen. The power circuit also has a peak power detect circuit which compares the phasing of the voltage and current and enables the circuit to maintain operation at maximum power by inhibiting any frequency increase when resonance operation is achieved.

Application Guide for Shunt Capacitors on Industrial Distribution Systems at Medium Voltage Levels

Abstract: Increased emphasis on energy conservation and reduction of purchased electric power bills have resulted in an increased awareness of the importance of capacitors on industrial systems. Larger banks of capacitors are being considered for installation and many questions relating to the application must be answered. Most of the commonly encountered factors relating to equipment selection, location on the system, protection, and switching criteria are reviewed. Motor terminal capacitor applications are also discussed. Economic justification for the purchase of the capacitors and harmonic resonance, as it relates to capacitor selection and application, are not included.

Super compensated voltage control of redundant D.C. power supplies

Abstract: A power supply system is disclosed wherein redundant D.C. power supplies are provided for a single load, each of the supplies being capable of providing full load current so that one of the supplies may be removed without interrupting power to the load. Each of the power supplies has a differential amplifier type of voltage regulator that includes a resistor in series with the output lead so that it is capable of varying the output voltage to compensate for lead and OR-ing rectifier drops.

Qualitative indices for the system voltage and reactive power control

Abstract: Both in off-line and in on-line operation of energy systems, the computer has become an important ally of the engineer. However, results of calculations often obscure properties of steady state of the network. What will the power system network reaction be if one or more nodal voltage varies? How will these variations be reflected at certain nodes? How can one find rapidly a good operating strategy, even if not the best? Answers could be given by using non-linear programming procedures. Nevertheless, fast solutions can be found if heuristic techniques are introduced. This paper proposes to provide the power engineer with a class of indices which clears qualitatively the steady state of energy system network.

Low-power monolithic COS/MOS dual-slope 11-bit A/D converter

Abstract: A single-chip, auto-zeroing, dual-polarity, single power supply A/D converter will be discussed, citing CMOS amplifier techniques used and performance results.