Showing papers on "Power factor published in 1969"

Real Time Control of System Voltage and Reactive Power

Abstract: This paper presents a centralized optimizing computational algorithm for the on-line control of voltage and reactive power. The body of the paper is divided into two parts.

Maximum power point tracker

Abstract: Apparatus for detecting the instantaneous power from a power source and operatively selectively disconnecting the power source from a load and a battery recharging circuit upon generation of a pulse from a power peak detector or a peak absence detector, power to the load being supplied by the battery when the power source is disconnected, battery overcharged protection controls further operating to override reset of the power switch, the power source being forced to supply a range of output voltage corresponding to that providing maximum power output of the source.

Analysis of Natural Half-Wave-Length Power Transmission Lines

Abstract: This paper provides additional theoretical information on half-wave-length power transmission. The analysis is rendered more general by consideration of a natural half-wave line instead of a short line tuned to half-wave. The effects of line loading and its power factor on the voltage and current profiles of the line and ganerator excitation have been included. Some of the operating problems such as charging of the line and synchronization of the half-wave system are also discussed. The inevitability of power-frequency overvoltages during faults is established. Stability studies have indicated that the use of switching stations is not beneficial. Typical swing curves are also presented.

Improvement of alternator stability by controlled quadrature excitation

Abstract: Operation of a synchronous generator at leading power factor has been severely limited in the past because of stability considerations. A regulator, acting on a normal direct-axis field winding, can only extend the range of stability when the generator is loaded, and has no effect under unloaded conditions. An additional winding on the quadrature axis, provided with a suitable control, can, however, ensure stable operation at any leading-power-factor load, within the heating limit of the generator. The most effective control uses a closed loop actuated by a signal derived from the load angle. The theoretical treatment in the paper consists of two parts. First, some general results are deduced from simplified equations, particularly relating to the limitations of a direct-axis regulator and the benefit of using an angle signal with the quadrature regulator. More complete computations are then made to obtain stability-limit curves for many alternative schemes. The work is concerned with the steady-state stability of a l-machine system, in which a generator is connected to an infinite bus through a reactance. Experiments to confirm the theoretical results were carried out on the micromachine equipment at Imperial College. The alternatives studied included simple proportionate regulators and more elaborate schemes using first- and second derivative elements, and the angle signal was taken alternatively from the infinite bus and the generator terminals. Good agreement was obtained with the corresponding computations.

Drive circuit for minimizing power consumption in inductive load

Abstract: Automatic power supply circuit design for driving inductive loads and minimizing power consumption including solenoid example

Divided-winding-rotor synchronous generator. A comparison of simulated 30 MW conventional- and divided-winding-rotor turbogenerators

Abstract: Experiment with a 5kVA machine showed the feasibility of a new form of turbogenerator using a rotor winding of two sections, in X formation, controlling the torque and reactive requirements separately.The performance of a conventionally wound rotor turbogenerator (c.w.r.) of 30MW size, described by Shackshaft, is compared with that of a divided-winding-rotor (d.w.r.) arrangement (CEGB patent application 2240/65) of the same machine.The analogue simulation shows that the d.w.r. can control power and reactive output satisfactorily, without altering the rotor position in relation to the generator air-gap flux. Fully rated stator current at leading power factor can be obtained continuously from no load to full load.The speed of response of the d.w.r.-generator reactive power to a step change of infinite-busbar voltage is, on average, twice that of the c.w.r. Turbogenerator stability is improved, and is shown to be independent of reactive generation or absorption, being affected only by active-power generation.Transient-stability comparisons are made by simulating 3-phase short-circuit faults close up to the high-voltage busbar, with low- and high-impedance connections to the infinite busbar.The c.w.r. simulation at full load with full excitation withstands a fault duration of 0.45s, which comes down, with reducing excitation, to 0.32s when Qu = − 0.225 p.u. and rotor angle = 70°; 0.2s when Qu = − 0.6 p.u. and rotor angle = 100°; and less than 0.1 s when Qu = − 0.9 p.u. and rotor angle = 120°.Comparable d.w.r. simulation of load and excitation conditions all require a fault duration exceeding 0.4s to cause instability. Even the Qu = − 2.3 p.u. condition is simulated without deterioration of control, and requires 0.4s fault duration to cause instability.The high-impedance connection to the infinite-busbar simulation shows, in general, that the maximum fault duration for each type of generator is reduced by 0.1s.

Oil-Immersed Power Transformer Overload Calculations by Computer

Abstract: Application of overload ratings to power transformers is considered in the light of 30 years of operating experience. A comprehensive description is given of the philosophy of overloading, methods of calculation, transformer life curves, and a working computer program which incorporates these factors with increased accuracy and reduced engineering time. Recommendations are made regarding life curves, ambient temperature selection, resistance correction for temperature variations, and daily load-cycle evaluation.

A Solid-State Supply for Induction Heating and Melting

Abstract: The paper describes a practical solid-state phase and frequency converter. Three-phase input power is converted to single-phase power of higher variable frequency output power, without the use of a dc link. A brief description of the circuit is given, followed by simplified theoretical considerations and actual experimental results.

Speed compensation motor circuit utilizing real current component

Abstract: An induction motor energization circuit id disclosed with energization from a variable frequency device such as an inverter. The load current to the induction motor has a considerable lagging power factor and a phase-sensitive detector detects only the in-phase or 180* out-of-phase component of this load current and applies it as a control to regulate the variable frequency device. The typical induction motor action is one where the speed droops because the slip increases as the torque increases and may be 2 to 3 percent of base speed. A signal such as the in-phase component of load current which is virtually proportional to torque is used in this invention to correct the frequency output of the inverter by 2 or 3 percent, therefore virtually eliminating the speed or slip error. By the present invention the use of only the real component of the motor load current as a feedback signal results in a substantially constant speed of the motor. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Generator load control system

Abstract: A control system for regulating the power output of a traction generator in response to the power capability of the diesel engine prime mover wherein feedback signals responsive to the generator output current and voltage are applied to the inputs of bridge rectifiers whose outputs are serially connected in a reference current circuit. A unidirectionally conducting circuit coupled across the bridge rectifiers provides a control signal to limit the generator load when feedback signals exceed the reference current. The reference current circuit includes in series connection a source of reference voltage whose magnitude corresponds to the power output level of the diesel engine, a resistance network and the bridge rectifier. Provision is made for retarding the rate at which the generator load is increased upon increases of diesel engine output power by a stepped increase of the resistance of the resistance circuit during an increase of diesel engine power. During such time a circuit, responsive to an increase of a reference voltage, opens a shunt connected in parallel with a portion of the resistance circuit. A capacitance connected serially across the load voltage source and a portion of the resistance network additionally shunt a portion of the reference current to prevent a stepped increase of reference current. A capacitance discharge circuit is operative during reductions of diesel engine power to prevent the capacitance circuit from affecting the rate of load control during such power reduction. This invention relates to a generator excitation control system and more particularly to a system regulating the power demand of a traction generator in response to the available power of a thermal prime mover, such as a diesel engine. Provision is made for controlling the rate at which the generator output is increased responsive to increasing diesel engine power output in order to reduce the generation of smoke by the diesel engine during increases of diesel engine power.

Electromagnetic induction apparatus for high-voltage power generation

Abstract: The power capability of insulating core-type transformers is greatly increased by creating additional magnetomotive force in certain secondary coils without any consequent power loss. At the same time, surge protection is provided for the primary power source without adversely affecting the auxiliary power source by using additional secondary cores with a resistive circuit isolating the high-voltage power supply from damaging highvoltage transient surges and providing artificial capacitance between the additional secondary cores and ground potential.

Load insensitive electrical device

Abstract: A class of power converters is disclosed for supplying direct current at one voltage from a source at another voltage which includes a simple passive circuit arrangement of solid-state switches, inductors, and capacitors by which the output voltage of the converter tends to remain constant in spite of changes in load. The switches are sensitive to the current flowing in the circuit and are employed to permit the charging of capacitance devices in accordance with the load requirements. Because solidstate switches (such as SCR''s) may be used with relatively high voltage and because of the inherent efficiency of the invention that permits relatively high switching frequencies, power supplies built in accordance with the invention, together with their associated cabling, can be substantially lighter in weight for a given output power level and efficiency of operation than systems of the prior art.

Static transfer switching system

Abstract: A static transfer system includes a first switch for connecting a normally used AC source to a lead and a second switch for connecting a standby source to the lead. A sensor is connected to an AC sine wave reference source for comparing at every instant of time the normal AC sine wave signal to the reference source signal and feeding an error signal to a logic circuit at any instant in time when the normal source signal falls below the reference signal. The logic circuit is effective to instantaneously connect the load to the standby source and disconnect the load from the normal source irrespective of the load power factor, and to reconnect the load to the normal source and disconnect the standby source from the load when the normal source is again capable of handling the load.

Tunable L-band high-power avalanche-diode oscillator

Abstract: An avalanche-diode oscillator that has achieved pulsed power output of 180 W at 1.3 GHz with 40% efficiency will be discussed. Frequency is tunable from 1.0-1.6 GHz with power variations less than 1 dB.

Phase sensitive motor circuit utilizing real current component

Abstract: An induction motor energization circuit is disclosed with energization from a variable frequency device such as an inverter. The load current to the induction motor has a considerable lagging power factor and a phase sensitive detector detects only the in-phase or directly out-of-phase component of this load current and applies it as a control to regulate the variable frequency device. At high frequency, the constant volts per cycle operation of the motor is satisfactory but at low speeds the usual energization system of adjusted constant volts per cycle results in overexcitation of the motor causing considerable losses and overheating. By the present invention the use of only the real component of the motor load current as a feedback signal results in considerably lower losses in the motor. The foregoing abstract is merely a resume of one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Solid-state ac power control apparatus

Abstract: A solid-state AC power control circuit intended for use with digital computers and which can increase or decrease, and turn on or turn off the AC power supplied to a work load in response to the application of computer generated electrical signals to the proper input terminal. The amount of power change is determined by certain characteristics of the signals and the RC time constant of a memory circuit in the device. In addition to input terminals for receiving power increase and decrease input signals, two other input terminals are provided for allowing the controlled power to be turned full off or back on to a preset level by the computer without disturbing the memory circuit.

Apparatus for providing uninterrupted power to a load

Abstract: Apparatus for switching power sources to a load without interruption is disclosed. The apparatus includes a source of rectified and filtered AC, a regulator, and a load. The AC source feeds DC power of given voltage to two terminals. A sensing and power delivery circuit is connected to these same two terminals to provide power from a DC source when the power from the AC mains suffers a degradation. The sensing and power delivery circuit includes a saturable switching transistor which switches the battery across the above-mentioned two terminals when a sensing circuit detects a change in the rectified and filtered AC. The sensing circuit controls a controlled rectifier which closes a current path around the battery permitting the switching transistor to saturate thereby effectively placing the DC source across the load terminals. A battery charging arrangement is also shown.

Optimal control of transients in a power system

Abstract: This letter investigates optimal control of transients in a nonlinear power system by means of the new approach of bang-bang control of reactance. The generality and utility of this control process are discussed and computational results are presented for a specific case.

Hook-on power factor, volt and ampere meter

Abstract: The split magnetic core or hook-on magnetic core of an alternating current measuring apparatus carries two separate and independent coils. By hooking the core on one-phase conductor of a three-phase electrical circuit and by supplying one coil with compensating current derived from the other phase conductors, the power factor of the circuit may be read on a meter connected to the other coil. By means of a suitable switching system, the core-coil-meter arrangement may also be used to measure either voltage or current in single-phase or polyphase circuits.

Self-starting power converter

Abstract: A STARTING SYSTEM FOR A SYNCHRONOUSLY COMMUTATED POWER CONVERSION UNIT. DURING START-UP A BRIDGE RECTIFIER IS CONNECTED AND OPERATED AS AN AC REGULATOR TO PROVIDE A VARIABLE REDUCED VOLTAGE TO THE SYNCHRONOUS CONDENSER. AFTER START-UP THE BRIDGE RECRIFIER IS RECONNECTED AS A PHASE DELAY RECTIFIER.

Transients in EHVDC Power Systems: Part I - Rectifier Fault Currents

Abstract: This paper presents a concise summary of results obtained from a rigorous analysis of the factors influencing the transient fault currents in an EHV rectifier terminal for a fault on the line side of the dc series reactor. The effect of the exact instant of fault occurrence after the time of completion of a commutation is shown to have special significance. It is also shown that the maximum transient peak currents, even for an "instantaneous" control system, may be on the order of 2.0 times nornal or more for representative dc series inductances when initial load is considered. For a less ideal or slower control system, greater maximum peak transient fault currents are found. Furthermore, saturation of the dc series reactor is shown to result in larger currents. Results for two and three bridges in series, as well as for a single bridge, are given in curve form for convenience of the user.

Proportional power control circuit

Abstract: A proportional power control circuit in which the average power applied to the load is controlled by controlling the number of cycles of power applied to a load in a series of available cycles of power. A proportional gate is generated for controlling the application of power to the load. The proportional gate is generated by a circuit which compares a reference voltage that varies in accordance with the demand for power with a ramp voltage whose potential varies as a function of time.

Design Equations for Dynamitron Type Power Supplies in the Megavolt Range

Abstract: The power supply which is used as the accelerating potential for megavolt Dynamitron accelerators is a parallel-fed, series-cascaded rectifier system. Low frequency RF voltage is capacitively coupled into the cascaded rectifier system by means of an SF-6 gas insulated electrode configuration. Maximum voltage attained with this configuration has been 5.7 MV. Maximum current attained has been 20 mA. Maximum beam power attained has been 40 kW. This paper covers the development of equations which express the operational input parameters such as, oscillator plate voltage, current, and power in terms of the required output high voltage and load current, and the internal circuit parameters such as, tank capacitance, tank inductance resistance, number of rectifier stages, and oscillating frequency. Calculated data from these equations agree closely with experimental data. This analysis allows the optimization of a power supply design in terms of critical parameters for a given maximum output voltage and load current.

Modes of Operation of Three-Phase Inverters

Abstract: Three-phase inverters have different modes of operation, while the load power factor angle varies over a 3600 range. A method of analysis is described which makes it possible to find these modes of operation. The method is based on the use of Park vectors. These vectors-generally used in the analysis of three-phase ac machines-are composed of the instantaneous values of a three-phase system. Voltage and current vectors of a three-phase inverter are used to find the current distribution of the inverter. An analysis is given of all the possible conditions of an inverter connected to an active load that can produce any load power factor from zero leading to zero lagging. Some special modes of operation are discussed in detail. Ranges of load power factor angles having different types of commutations are obtained. A control method is shown which makes it possible to obtain effective voltage regulation at the full range of load power factor at a reduced commutation frequency.

Device for coupling a transducer to a transmitter and receiver (u)

Abstract: The large capacitive reactance of piezoelectric materials such as, barium titanate, Rochelle salt, or quartz, that are used as the driving elements in transducers has required large inductances to bring the power factor to unity to ensure efficient power transfer between a transducer and a transceiver. A transmitter-transformer couples a transmitter to the transducer, at high-energy output levels, and a series connected receiver-transformer, tuned to pass signals with an identical frequency characteristic at significantly lower levels of energy, eliminates a problem arising when one transformer is used. When employing a single transformer having a high permeability core, its inductance varies when the transformer transfer energy separated levels of energy thusly changing the tuning of associated circuits at these different levels of operation. Shunting switches across the transmitter-transformer winding and the receiver-transformer winding, enable the selective disconnection of either of the transformers from a common coupling circuit when the other mode of operation is proceeding. A pair of back-to-back diodes forming the shunting circuit across the primary of the receiver-transformer, have a forward voltage drop greater than the magnitude of the received signal to ensure the transfer of received signals when they appear across the primary winding. These same diodes have a forward voltage drop far below the level of the high-power output appearing across the secondary winding of the transmitter-transformer to ensure that this signal is shorted around the primary of the receivertransformer to eliminate the possibility of damaging the inherently more delicate receiver-transformer.

High power square wave sustaining generator for capacitive load gas discharge panels

Abstract: THERE IS DISCLOSED A HIGH POWER SQUARE WAVE SUSTAINING GENERATOR SYSTEM FOR A GAS DISCHARGE PANEL PARTICULARLY OF THE TYPE IN WHICH DISCHARGE SITES IN A THIN GASEOUS DISCHARGE MEDIUM CONFINED IN A SPACE BETWEEN A PAIR OF DIELECTRIC CHARGE STORAGE MEMBERS ARE DEFINED BY A PAIR OF MATRIX CONDUCTOR ARRAYS. THYRISTOR PAIRS ARE SERIES CONNECTED ACROSS A HIGH DIRECT CURRENT VOLTAGE POTENTIAL SOURCE WITH AN INTERMEDIATE POINT BETWEEN THE THYRISTOR PAIR BEING CONNECTED TO CONDUCTORS OF ONE OF THE ARRAYS. A SECOND THRYSTOR PAIR IS SERIES CONNECTED ACROSS A SECOND SOURCE OF HIGH VOLTAGE DIRECT CURRENT POTENTIAL OF OPPOSITE POLARITY TO THAT OF THE FIRST SOURCE. A FREE-RUNNING MULTIVIBRATOR OPERATING AT DOUBLE THE DESIRED FREQUENCY OF OUTPUT OF SQUARE WAVES HAS ITS OUTPUT DIVIDED BY A BISTABLE FLIP-FLOP CIRCUIT AND TWO OUTPUT VOLTAGES (EACH THE COMPLEMENT OF THE OTHER) FROM THE FLIP-FLOP ARE FED TO ONE-SHOT MULTIVIBRATORS AND THE OUTPUT OF THE ONE-SHOT MULTIVIBRATORS ARE USED AS CONTROL OR TRIGGER POTENTIALS FOR THE GATE ELECTRODES OF THE THYRISTORS. SUCH CONTROL POTENTIALS ARE APPLIED AS TRIGGER POTENTIALS TO THE GATE ELECTRODE OF ONE THYRISTOR OF A PAIR TO CAUSE IT TO CONDUCT AND A BLOCKING POTENTIAL IS APPLIED TO THE GATE ELECTRODE OF THE OTHER OF THE THYRISTORS TO MAINTAIN IT NONCONDUCTIVE WHEREBY CURRENT FLOWS FROM THE FIRST HIGH VOLTAGE SOURCE TO THE CAPACITIVE LOAD THROUGH THE CONDUCTIVE THYRISTOR AND ON APPLICATION OF A TRIGGER POTENTIAL TO THE SECOND THYRISTOR OF THE PAIR AND A BLOCKING POTENTIAL TO THE FORMERLY CONDUCTING THYRISTOR, THE SECOND THYRISTOR OF THE SERIES PAIR IS CAUSED TO CONDUCT THEREBY DISCHARGING CURRENT FROM THE LOAD. THE OTHER CONDUCTOR ARRAY OF THE PAIR IS SUPPLIED WITH SQUARE WAVE POTENTIALS IN A SIMILAR MANNER BUT OF OPPOSITE POLARITY. TRANSFORMERS HAVING DOUBLE SECONDARIES ARE USED TO SIMULTANEOUSLY SUPPLY TRIGGER POTENTIALS TO THE GATE ELECTRODES OF THE THYRISTORS WHICH ARE DESIRED TO BE CONDUCTIVE TO THEREBY SUPPLY CHARGING CURRENT TO THE PANEL AND A BLOCKING POTENTIAL TO THE GATE ELECTRODE OF THE OTHER THYRISTORS TO RENDER THEM NONCONDUCTIVE. A PROTECTION CIRCUIT IS ALSO PROVIDED IN THE EVENT BOTH THYRISTORS OF A SERIES PAIR ARE RENDERED CONDUCTIVE AT THE SAME TIME. IN ADDITION, THERE IS DISCLOSED A SERIES LOSSY INDUCTOR IN THE CIRCUIT TO THE CONDUCTOR ARRAYS TO LIMIT PEAK CURRENT AND RING CURRENTS TO THE LOAD. CONSULT THE SPECIFICATION FOR OTHER FEATURES AND DETAILS.

Pan-Africanism—Land and Power

Abstract: (1969). Pan-Africanism-Land and Power. The Black Scholar: Vol. 1, The Culture of Revolution, pp. 36-43.