Showing papers on "Power factor published in 1972"

Electric power systems

Abstract: Basic Concepts Components of a Power System Control of Power and Frequency Control of Voltage and Reactive Power Load Flows Fault Analysis Stability Limits Direct Current Transmission Overvoltages and Insulation Requirements Overhead Lines and Underground Cables Protection Appendices Index.

Equilibrium Analysis of Power Systems

Abstract: The flow function of a power system is the vector of node powers expressed in terms of the node angles The Jacobian is the matrix of partial derivatives of the flow vector with respect to the angle vector The ratio of the determinant of the Jacobian to the value which it has when the node angles are set to zero is a dimensionless stability margin which lies between one and zero (steady-state in- stability) and is easily computed from a load flow The margin of torque is the least change in power flows that will cause instability Maximizing the torque margin or maximizing the stability margin with a load constraint yields the optimum dispatching change to maximize security

Optimum Load-Frequency Continuous Control with Unknown Deterministic Power Demand

Abstract: Since the incremental power demand in a power system is not always apriori known, direct application of the optimum linear- state regulator to load-frequency control is not possible Furthermore, load-frequency control generally requires the use of an integral type control operation to meet the system operating specifications This requirement is introduced into the formulation of the optimum load- frequency control problem presented in this paper

Stability Analysis of Power Systems

Abstract: A procedure for locating directly the lowest saddle point of the potential energy function associated with a power transmission network is presented. This procedure is used to compute a margin of stability that specifies the maximum asynchronous transient energy that can be retained by the system while in synchronism. The potential function is shown to be convex in the principal region of the angle space. A unique solution is shown to exist for the load flow problem if the algorithm of solution is initiated at the origin.

Effects of Power Supply Variations on AC Motor Characteristics

Abstract: Voltage level variations are shown to be only one of eight different types of voltage deviations which can affect motor characteristics. Each of these is discussed in relation to possible detrimental effects on operating costs or motor reliability. The timeliness of the paper is demonstrated, especially for continuous process and automated industries. Remedial measures, when indicated, are shown to cover a wide gamut from redesigning control systems to reappraising the electrical system one line diagram.

Power regulation by means of a switched capacitor

Abstract: A bridge of four solid-state switches with a capacitor in one diagonal is connected in series between the supply and the load. The switches (thyristors) periodically reverse the current-flow direction through the capacitor. The load power is controlled by varying the switching frequency. The device may be used for the control of direct current and alternating current.

Multiple output alternator

Abstract: A multiple output alternator having separate sets of power coils mounted on the stator adapted to be magnetically excited by a rotor having a direct current field coil is provided for a vehicle. The separate power coils being in a cooperative relation to give a distributed load condition when the rotor is driven by the variable speed power unit of the vehicle. Rectifying and voltage regulating means are provided for both sets of power coils to provide a high and low wattage power source, with the field coil of the rotor being supplied with a regulated D.C. voltage from the high wattage power source which also supplies power to the conventional electrical system of the automotive vehicle. For example, two power sources from an alternator are adapted to be used for charging batteries in a power system having two storage batteries which supply power to circuits requiring differing voltages, a relatively low voltage circuit which may include the high wattage power source and one of the batteries and a relatively high voltage circuit which is supplied by both storage batteries in series connection for special purposes such as starting of the variable speed power unit. More than two outputs could be supplied if desired.

AC to RF converter circuit for induction cooking unit

Abstract: A first feedback path is connected across one of the commutating reactive components of an induction cooking unit chopper inverter for deriving a first high frequency alternating current gate controlling signal voltage at substantially the operating frequency of the chopper-inverter. A second feedback path is connected to the high voltage power supply terminals for deriving a second alternating current gate controlling signal voltage at the frequency of the high voltage potential appearing across the high voltage power supply terminals including the low frequency, undulating, full wave rectified 120 hertz excitation potential component supplied by the full wave rectifier bridge. A gating signal generator is provided for deriving high frequency output gating signal pulses of sufficient magnitude to assure safe turnon of the power rated thyristor and is energized from the low voltage direct current power supply. A first control switch is coupled to and enables operation of the gating signal generator and includes a direct current bias circuit supplied from the low voltage direct current power supply for supplying direct current bias potential to the first control switch. A common alternating current coupling path comprising a differentiating circuit supplied with both the first feedback high frequency alternating current gate controlling signal voltage and the second feedback alternating current gate controlling signal voltage, differentiates the two feedback gate controlling signals and supplies the differentiated output in common to the first control switch to control operation of the first control switch in conjunction with the direct current bias potential. The circuit arrangement provides zero point switching during initial turn-on of the thyristor at or near the zero point of the high voltage full wave rectified excitation potential supplied across the high voltage power supply terminals, and both unity power factor and unity form factor operation whereby sinusoidal line current is drawn for all values of loading from no-load to full-load and without requiring substantial supply line filtering components.

Electric power supply system using back-up capacitor

Abstract: Herein disclosed is an improved d-c power supply system which comprises a d-c power source, a first rectifier serially connected to the power source, and series connection composed of a protective resistor and a back-up capacitor, the series connection being connected across the first rectifier and the power source, and the protective resistor being bypassed by a second rectifier so that a discharge current from the back-up capacitor flows through the second rectifier. The power supply system further comprises means for producing information signals representing condition of the back-up capacitor.

An Evaluation of the Three-Voltmeter Method for AC Power Measurement

Abstract: The accuracy and frequency response limitations in the present square-law responding laboratory wattmeters have promoted the search for alternate methods of ac power measurement using electronic instrumentation. The three-voltmeter method is based on an old principle of operation implemented by new analog circuitry. Results of the tests reported here show a precision of power calculation with 0.01 percent error at frequencies below 5 kHz. A unique test procedure is described for the comparison of the three-voltmeter device and a time-division multiplier wattmeter operating at zero power factor.

Ac-dc generating system

Abstract: An induction machine driven as a generator has its output connections coupled to the output connections of a static inverter circuit, connected to operate not as an inverter but as a switching system. A capacitor is coupled to the bus conductors of the switching system. D-c excitation is furnished to the induction generator system only for starting, and is then disconnected. At rated speed the static inverter circuit operates as a switching system to regulate connection of the capacitor to the induction generator on a time-sharing basis, replacing the directly connected capacitor bank in known systems. In multiphase systems the capacitor is not required, as the switching system periodically directs the flow of reactive energy from one phase to another of the inductive machine. By regulating the frequency of the switching operation the overall system can be made to generate effectively over a wide range of input speeds. An a-c output voltage is available from the common terminals between the induction generator and the switching system, and a d-c output voltage is also available from separate conductors of the switching system.

Adjustable speed induction motor system

Abstract: An electric induction motor/control system providing the desirable high starting torque and wide speed characteristics of direct current motors. The stator of the induction motor has two specially interrelated winding sets per phase. The motor windings are supplied with unidirectional current pulses from silicon controlled rectifiers that are programmed to provide advantageous modes of operation for the motor. The unique relation and interaction between the motor windings hereof and the associated electronic circuitry results in high power factor, good efficiency, and self-clearing SCR commutation action. The preferred motors use a squirrel cage rotor with no commutator, brushes, or slip rings. The complementary stator winding arrangements are not voltage limited, and thereby permit the construction of large power motor systems. Practical motor ratings are from fractional to over 500 horsepower, at speeds ranging from 600 to 40,000 rpm, and higher. With selective control circuitry the motors hereof can be operated: (a) at constant output torque over a wide speed range; (b) at constant horsepower over a selected speed range; (c) with traction output characteristics similar to that of series motors; (d) at constant speed; (e) and with direct speed reversal in any of these modes. The motor systems require little maintenance, and may be hermetically sealed.

Circuit for instant restart of high pressure discharge lamp

Abstract: In the running condition, a high pressure lamp is connected in series with an inductive reactor across the line (240 volts), and a power factor correcting capacitor is connected across the line. To assure instant starting whether the lamp is hot or cold, an igniter is energized which injects kilovolt radio frequency pulses in series with the reactor open circuit voltage across the lamp, and the reactor open circuit voltage is boosted a predetermined factor up to 3 X line voltage by temporarily connecting the power factor correcting capacitor to a tap in the inductive reactor.

Reactive power compensation control system

Abstract: A reactive power compensation control system is provided for a three phase ac electric power supply system which exhibits power factor changes when subjected to large reactive draws by dynamic reactive loads. The control system comprises four capacitor banks switchable in or out of the power system by solid state switches. Each capacitor bank comprises three delta connectible capacitors, one capacitor for each pair of phase lines, and each capacitor is switched by one solid state switch. Each solid state switch comprises a pair of inverse parallel connected SCR''s. Each solid state switch is controlled by an individual firing circuit which comprises a charging circuit (for operating the charging SCR) and a discharging circuit (for operating the discharging SCR). All 12 firing circuits are controlled by a control circuit which comprises a KVAR transducer coupled to the power supply system for sensing reactive power conditions therein and ON and RUN circuits which operate the firing circuits.

A Study of Asymmetrical Gating for Phase-Controlled Converters

Abstract: The low power factor of phase-controlled converters when the output voltage is less than the maximum is of-concern in high-power equipment. In a converter consisting of two commutating groups in cascade, the usually low power factor can be improved by firing or gating the thyristors in the two groups asymmetrically. One of the groups is fully advanced (or retarded) to minimize its reactive power, while the other group is controlled to give the desired dc Output. The technique is not recommended for single three-phase bridge converters because of third-hannonic output ripple, second-harmonic line current distortion, and danger of commutation failure. These objections are overcome by combining pairs of three-phase bridges. When regeneration is not required, half of the thyristors can be replaced by diodes, reducing the cost. The method should offer substantial improvement in the power factor of cycloconverter ac motor drives as well as dc motor drives.

Microwave oven power supply circuit

Abstract: A microwave oven power supply includes a synchronous switch and a phase control circuit. The switch is electrically connected in series with the supply lines which, until actuated, maintains normally open the path for current flow to the transformers and other electrical components found within the oven power supply. An On-Off switch and interlocks are in series with the power line and an electrical circuit completed through the phase control circuit inhibits the operation of the power circuit until it is desired to commence cooking operations. The phase control circuit determines the proper phase of the applied line voltage for which the synchronous switch should be initiated. By design, this phase control circuit is matched to the transformer characteristics and senses the magnitude of the applied line voltage so that initial conduction of the synchronous switch falls within a preselected range which has been determined to minimize transient voltage spikes and/or in-rush current transients. In this way, the initiation of current flow in the high voltage transformer and filament transformer and other oven elements is delayed until the sinusoidal voltages of the power line are in the phase relationship that I have determined to be proper.

System for the electric supply of a variable capacitive load

Abstract: System for the electric supply of a variable capacitive load by means, for each of the phases of the load, of an independent inverter comprising controlled rectifiers such as thyristors, which is connected by its input terminals to a direct-current source, which may be a rectifier, and by its output terminals to the terminals of a matching network whose output terminals are connected to the load. The matching network is formed of a capacitor connected to the input terminals of the matching network, a transformer having a high magnetising current, a filtering circuit comprising two inductances of which one is connected in parallel with the same terminals as those of the capacitor and the other in series in the circuit connecting one terminal of the capacitor to the corresponding terminal of the primary winding of the transformer. The terminals of the secondary winding of the transformer are connected to the terminals of the load.

Apparatus for limiting instantaneous inverter current

Abstract: The invention relates to a technique for limiting the peak transient currents in the power switches of an inverter wherein a current control circuit compares the current flow in the power switches of the inverter to a reference value and provides protective ON-OFF control of the power switches to prevent overload of the power switches. In the event the current flow through a power switch exceeds a predetermined value, the current control circuit overrides the main power switch ON-OFF control circuit and generates an inhibit signal which turns the power switch off for a period of time required to allow the current magnitude to decrease a predetermined amount at which time the current control circuit inhibit signal is removed and the main power switch ON-OFF control circuit resumes control of the power switch conduction.

Amp-hour meter

Abstract: A submersible having a bank of storage batteries for power is provided with a circuit giving crewmen a real-time indication of power used or power remaining in the batteries. A sensor element interposed in series with the load created by the submersible's machinery bleeds off a small sample of the load current which is proportional to the power drain of the machinery. An integrator circuit coupled to a unijunction transistor functions as a relaxation oscillator to generate pulses at a rate proportional to the magnitude of the load current and to pass them to a circuit for producing counter pulses. Counter pulses are coupled to a digital read-out for providing a visual indication of power used or power remaining in the batteries and also are fed-back to the integrator circuit to repeatedly reset it during the integration sequence. Increased reliability is ensured by the provision of a biasing-circuitry arrangement which is "on" only during the period when load current is being drawn from the bank of storage batteries.

Light-triggered electric power source

Abstract: An electric power source for delivering a controllable voltage to a load. It has low power loss and is capable of acting as a programmable source of electric energy, one which can be used, for example, to furnish a very high-voltage output from a lightweight system. The power source is a modular type structure in which the apparatus is made up of a number of identical stages or modules connected in cascade. Each stage includes a voltage supply and floating reference voltage means connected to the supply. The voltage supply is connected to the output of the source through bilateral, solid-state switches along alternate electrically conductive paths which connect either one side or the other of the voltage supply to the output. A bistable circuit serves to control the bilateral switches, triggering of the bistable circuit being effected by radiation impinged upon light sensitive devices, the devices being connected to perform a setreset type function of the circuit. The floating reference voltage provides a constant electric potential for switching purposes. The system can be used to step up a voltage, and a form thereof can be used to step a voltage down.

Regulated dc-dc power supply

Abstract: An improved direct-current power supply is provided for converting alternating-current power or direct-current power into direct-current power, and which has particular utility in energizing electronic equipment such as computers, data processors, and the like. The power supply of the invention is a regulated fly-back type in which electric energy from an appropriate source is alternately stored in an electromagnetic device, such as a transformer, and then released into a load. The improved power supply of the invention includes control circuitry which causes a constant amount of energy to be stored during each cycle independently of source voltage, and which enables the power supply to exhibit highly favorable regulation characteristics through a wide range of loads.

Low voltage appliance protector

Abstract: A method and apparatus for disconnecting a load from a power source when the voltage from the power source falls below a first predetermined level and for reconnecting the load to the power source when the voltage rises above a second predetermined level. The voltage of the power source is constantly sensed and when the voltage falls below a first predetermined level a switch means, which is connected between the power source and the load, is opened, thereby disconnecting the load from the power source. An auxiliary coil is placed in series with the load so that, when a load drawing an initially large current is connected to the power source, the increased current through the auxiliary coil produces a magnetic force to hold the switch means closed even though a voltage below the first predetermined level is sensed. In this manner, false disconnection of the load from the power source is prevented.

Capacitor charging circuit

Abstract: A capacitor is repetitively charged and discharged for use in flash tube apparatus, or the like. An AC supply is utilized and current from the AC supply is maintained substantially constant while the charging current is made to vary with time to achieve a substantially constant power charge rate while maintaining a nearly unity power factor on the AC supply.

Electromagnetic implosion x-ray source

Abstract: An electromagnetic implosion X-ray source having a thin cylindrical metal foil supported on spaced electrodes within an evacuated chamber. The electrode system is connected through a switch to a capacitor bank power supply with low inductance leads and with the average electrical impedance of the dynamic plasma being matched to the impedance of the power supply. An X-ray radiation path is provided between the X-ray source and a sample holder attached to the X-ray source.

Controlling Generator MVAR Loadings Using a Static Optimization Technique

Abstract: The utilization of EHV networks and underground cables in today's modern power system has created a reactive power control problem. In particular, system generators are being forced to absorb large quantities of reactive power to maintain system voltage.

Standby power source for an ac alarm system

Abstract: A standby power source connected to AC power mains for supplying AC power to an AC alarm system when there is a main power failure comprises a source of DC power, inverter means for converting DC power to AC power and controlled switching means for connecting the source of DC power to the inverter means and for transferring the connection of the AC alarm system from the AC power mains to the inverter means at the time of a power failure.

Synchronous dc power supply

Abstract: A synchronous direct current (dc) power supply has the power supply input drive synchronized with the pulse repetition frequency (PRF) of the amplifying or load circuit requiring the dc power for operation. This limits the occurrence of ripple components in the power supply output to the spectral positions of the PRF lines, eliminating ripple interference with signal processing in the load. An astable multivibrator is synchronized with the PRF generator output frequency. The multivibrator output is converted to a square wave, filtered, and processed to provide a fully rectified output voltage for coupling to the desired load circuit.

Analysis of Power System Faults by Phase Impedance Matrix Method: I - General Fault Analysis

Abstract: The analysis of unbalanced power systems depends usually on transformation methods by which the phase quantities are substituted by, for example, symmetrical component quantities. These transformations had the computational advantages in the past, but with the use of digital computer, they no longer appear to be necessary. In this paper the analysis of power system faults including the simultaneous ones has been undertaken with the help of phase coordinates, i. e., the actual system phase voltages, currents and impedances. This approach is found to be simple and readily adaptable to digital computer techniques. Symmetrical components are, however, used as a measure of the system unbalance.

High frequency power generator

Abstract: A static inverter system capable of providing ac. power at frequencies as high as 10 KHz. is characterized by an exceptionally high power factor and efficiency and employs one or more capacitive storage circuits on a time sequenced basis to cyclically and successively charge from a dc. power supply and discharge through an ac. load. The storage circuit charge via respective thyristors and the sequencing is affected by sequentially gating the thyristors with fast rise time, short duration firing pulses so that very short charging time constants may be selected without danger of damaging the thyristors or upsetting the desired sequencing.

Frequency-Modulated Fault Locator for Power Lines

Abstract: This paper describes the use of frequency-modulated radar techniques for accurate location of faults on power transmission lines. It includes the design of a prototype frequency-modulated fault location system. Test results of this system operating on a simulated transmission line are also included.