Showing papers on "Power factor published in 1985"

Electric power distribution system engineering

Abstract: Distribution System Planning and Automation Introduction Distribution System Planning Factors Affecting System Planning Present Distribution System Planning Techniques Distribution System Planning Models Distribution System Planning in the Future Future Nature of Distribution Planning The Central Role of the Computer in Distribution Planning Impact of Dispersed Storage and Generation Distribution System Automation Summary and Conclusions References Load Characteristics Basic Definitions The Relationship Between the Load and Loss Factors Maximum Diversified Demand Load Forecasting Load Management Rate Structure Problems References Application of Distribution Transformers Introduction Types of Distribution Transformers Regulation Transformer Efficiency Terminal or Lead Markings Transformer Polarity Distribution Transformer Loading Guides Equivalent Circuits of a Transformer Single-Phase Transformer Connections Three-Phase Connections Three-Phase Transformers The T or Scott Connection The Autotransformer The Booster Transformers Amorphous Metal Distribution Transformers Problems References Design of Subtransmission Lines and Distribution Substations Introduction Subtransmission Distribution Substations Substation Bus Schemes Substation Location The Rating of a Distribution Substation General Case: Substation Service Area with n Primary Feeders Comparison of the Four-and Six-Feeder Patterns Derivation of the K Constant Substation Application Curves Interpretation of the Percent Voltage Drop Formula Supervisory Data and Data Acquisition Advanced SCADA Concepts Advanced Developments for Integrated Substation Automation Capability of Facilities Substation Grounding Transformer Classification Problems References Design Considerations of Primary Systems Introduction Radial-Type Primary Feeder Loop-Type Primary Feeder Primary Network Primary-Feeder Voltage Levels Primary-Feeder Loading Tie Lines Distribution Feeder Exit: Rectangular-Type Development Radial-Type Development Radial Feeders with Uniformly Distributed Load Radial Feeders with Nonuniformly Distributed Load Application of the A,B,C,D General Circuit Constants to Radial Feeders The Design of Radial Primary Distribution Systems Primary System Costs Problems References Design Considerations of Secondary Systems Introduction Secondary Voltage Levels The Present Design Practice Secondary Banking The Secondary Networks Spot Networks Economic Design of Secondaries Unbalanced Load and Voltages Secondary System Costs Problems References Voltage Drop and Power Loss Calculations Three-Phase Balanced Primary Lines Nonthree-Phase Primary Lines Four-Wire Multigrounded Common Neutral Distribution System Percent Power (or Copper) Loss A Method to Analyze Distribution Costs Economic Analysis of Equipment Losses Problems References Application of Capacitors to Distribution Systems Basic Definitions Power Capacitors Effects of Series and Shunt Capacitors Power Factor Correction Application of Capacitors Economic Justification for Capacitors A Practical Procedure to Determine the Best Capacitor Location A Mathematical Procedure to Determine the Optimum Capacitor Allocation Capacitor Tank Rupture Considerations Dynamic Behavior of Distribution Systems Problems References Distribution System Voltage Regulation Basic Definitions Quality of Service and Voltage Standards Voltage Control Feeder Voltage Regulators Line-Drop Compensation Distribution Capacitor Automation Voltage Fluctuations Problems References Distribution System Protection Basic Definitions Overcurrent Protection Devices Objective of Distribution System Protection Coordination of Protective Devices Fuse-to-Fuse Coordination Recloser-to-Recloser Coordination Recloser-to-Fuse Coordination Recloser-to-Substation Transformer High-Side Fuse Coordination Fuse-to-Circuit-Breaker Coordination Recloser-to-Circuit-Breaker Coordination Fault Current Calculations Fault Current Calculations in Per Units Secondary System Fault Current Calculations High-Impedance Faults Lightning Protection Insulators Problems References Distribution System Reliability Basic Definitions National Electric Reliability Council Appropriate Levels of Distribution Reliability Basic Reliability Concepts and Mathematics Series Systems Parallel Systems Series and Parallel Combinations Markov Processes Development of the State Transition Model to Determine the Steady-State Probabilities Distribution Reliability Indices Sustained Interruption Indices Other Indices (Momentary) Load-and Energy-Based Indices Usage of Reliability Indices Benefits of Reliability Modeling in System Performance Economics of Reliability Assessment Problems References Electric Power Quality Basic Definitions Definition of Electric Power Quality Classification of Power Quality Types of Disturbances Measurements of Electric Power Quality Power in Passive Elements Harmonic Distortion Limits Effects of Harmonics Sources of Harmonics Derating Transformers Neutral Conductor Overloading Capacitor Banks and PF Correction Short-Circuit Capacity or MVA Bus Voltage Rise and Resonance Harmonic Amplification Resonance Harmonic Control Solutions Harmonic Filter Design Load Modeling In The Presence Of Harmonics Problems References Appendix A: Impedance Tables for Lines, Transformers, and Underground Cables Appendix B: Graphic Symbols Used in Distribution System Design Appendix C: Glossary for Distribution System Terminology Appendix D: The Per-Unit System Notation Answers to Selected Problems Index

Power supply for body implant and method of use

Abstract: An implanted blood pump system is described wherein power for driving the pump is provided by a transcutaneous transformer having an external primary winding and an implanted secondary winding. Control of the driving voltage to the pump is provided by an implanted shunt regulator. Voltage applied to the primary winding is controlled in accordance with the power factor sensed in the primary winding.

An SCR Inverter with an Integral Battery Charger for Electric Vehicles

Abstract: A thyristor-based inverter/charger for use in electric passenger vehicles is described, and prototype charger test results are presented. A battery charger is included integral to the inverter by using a subset of the inverter power circuit components. The integral charger employs the inverter commutation components as a resonant ac/dc converter rated at 3.6 kW. The resulting charger provides electrical isolation between the vehicle propulsion battery and ac line and is capable of charging a 25-kWh propulsion battery in 8 h from a 220-V ac line. Charger efficiency and power factor at an output power of 3.6 kW are 86 and 95 percent, respectively. The inverter, when operated with a matching polyphase ac induction motor and nominal 132-V propulsion battery, can provide a peak shaft power of 34 kW (45 hp) during motoring operation and 45 kW (60 hp) during regeneration. Thyristors are employed for the inverter power switching devices and are arranged in an input-commutated topology. This configuration requires only two thyristors to commutate the six main inverter thyristors. The combined ac inverter/charger package weighs 47 kg (103 lb).

PWM Control Techniques for Rectifier Filter Minimization

Abstract: Minimization of input/output filters is an essential step towards manufacturing compact low-cost static power supplies. Three PWM control techniques that yield substantial filter size reduction for three-phase (self-commutated) rectifiers are presented and analyzed. Filters required by typical line-commutated rectifiers are used as the basis for comparison. Moreover, it is shown that in addition to filter minimization two of the proposed three control techniques improve substantially the rectifier total input power factor.

A Novel Sinewave in AC to DC Converter with High-Frequency Transformer Isolation

Abstract: A novel Switch-Mode-Rectifier (SMR) structure is proposed and analyzed in this paper The proposed converter structure employs a high-frequency sine PWM cycloconverter to provide high-frequency ohmic isolation between the source and the load Furthermore, it draws high-quality current from the ac source thus requiring only small input reactive components Consequently, the proposed converter structure exhibits high power density and has low implementation cost

Variable speed constant frequency generating system

Abstract: A variable speed constant frequency generating system for generating constant frequency electrical output power from a variable speed source of motive power includes an exciter for generating excitation current, a main generator for developing the output power, both of the exciter and main generator being driven by a shaft coupled to the motive power source and power converters mounted on the shaft to transfer power between the exciter and the main generator. At shaft speeds below synchronous speed, i.e. that speed which would produce the desired output frequency when DC power is coupled to the main generator field windings, the exciter output is rectified and inverted so that alternating current power of proper frequency is delivered to the field windings of the main generator to maintain the output of the generator at a constant frequency. At synchronous speed, the power converters transfer substantially only DC power to the main generator windings. At speeds above synchronous speed, power is returned back to the exciter to cause same to operate as a motor and apply negative torque to the shaft and thereby maintain the output power at the desired frequency.

An Adaptive Power Factor Controller for Three-Phase Induction Generators

Abstract: An adaptive power factor controllerfor three-phase inducti on generators (and also for motors) is proposed in this paper. The controller senses the reactive current drawn by the machine and accordingly provides the needed reactive power to improve the power factor to as close to unity as possible. The controller is a modular, low-cost, harmonic free device. It does not create any transients in line current. It is designed to eliminate the self-excitation problems associated with induction generators. The controller is tested on an induction generator, which is being used in wind energy and similar applications.

Power source device for a load with a stand-by power supply system

Abstract: A power source device according to this invention comprises a voltage and phase detector for detecting the voltage and phase of a power supply system, a first controller for controlling an inverter so that an output of the inverter may agree with either a reference voltage and a reference phase or with the voltage and the phase of the power supply system, a second controller for switching the inputs of the first controller from the reference voltage and phase to the power supply system voltage and phase, or vice versa, when the phases of a reference oscillator and the power supply system have agreed, and a third controller for switching the power to a load from the inverter to the power supply system, or vice versa, when the synchronism between the inverter output and the power supply system has been detected.

A low voltage power source power inverter for an electroluminescent device

Abstract: A power inverter for an electroluminescent device is disclosed which enables the electroluminescent device to be powered from a low voltage DC power source. Switching transistors convert the low voltage DC power to low voltage AC power which is subsequently increased and coupled to a resonant circuit including the electroluminescent device. Current in the resonant circuit is sampled, referenced to half the low voltage DC power, and coupled back in phase to an amplifier and switching transistors to create an oscillator which oscillates at a frequency determined by the resonant circuit.

Power supply system and a control method thereof

Abstract: A power supply system including an inverter, a reserved power source and changeover switches for outputting one of outputs of the inverter and reserved power source to supply a load current to a load. The system further includes a control circuit for controlling a phase, a frequency and a voltage of the output of the inverter to coincide with a phase, a frequency of the output of the reserved power source and a specified voltage, respectively. The specified voltage is determined to be a predetermined reference voltage when the load current is below a detection level and to be a reduction voltage decided between zero volt and the voltage of the reserved power source when the load current is equal to or more than the detection level. A method for controlling a power supply system described above is also disclosed.

A Novel Bilateral Power Conversion Scheme for Variable Frequency Static Power Supplies

Abstract: PWM voltage source inverters (VSI's) supplied from diode rectifiers are employed with most of today's static power supplies for variable frequency ac type loads. This method generates nonsinusoidal input and output voltage/current waveforms and yields poor system reliability. An upgraded method of power conversion is presented that eliminates both problems. In addition, it allows bidirectional power flow which improves efficiency and simplifies cooling requirements. The subject method requires a PWM rectifier and a PWM current source inverter. Advanced PWM techniques employed with both static Converters allow the minimization of all associated passive components.

Reserve power source with power failure detection apparatus

Abstract: A reserve power source, switchably connected to a network between a primary power supply and a load, provides an auxiliary power signal to the load when a power failure condition is detected in the signal from the primary power supply. The reserve power source includes a circuit for instantaneously detecting and switching upon the occurrence of a power outage. An overvoltage/noise detector circuit is included to detect when either a sustained overvoltage condition or a high, short duration overvoltage condition occurs. A low voltage detector circuit is included for detecting a low voltage, or brown-out, condition. When an overvoltage or low voltage condition is detected, a preferred embodiment of the invention switches the load to the auxiliary power signal within one-half cycle of, but in zero-crossing synchronization with, the primary power signal.

Study of a resonant converter using power transistors in a 25KW x-rays tube power supply

Abstract: This paper describes a converter whose purpose is to feed an χ-rays tube (25 KW, 140 KV) from the industrial main power supply (380 V, 50 Hz). The authors justify the structure of this generator that is constituted by an inverter using power transistors and a transformer-voltage multiplier set which are connected by a series resonant circuit. The control logic of the transistors gives them the dual properties of these of thyristors. An accurate analytical study of this system allows to predetermine the characteristics of this converter now in its industrialization phase.

Computer-attached uninterruptable DC power supply

Abstract: A DC power supply comprising a sealed lead-acid battery, a charging regulator, a discharge pass element, an output power switch for disconnected the power supply from the computer and four light-emitting diode indicators which display the condition and trend of the battery charge state. The power supply may be permanently attached to an Apple IIc brand computer without marring the computer's plastic housing by means of tabs on upper and lower projections of the power supply housing which interlock with slots on the upper and lower surfaces of the computer's housing. The power supply also features an electronic "sleep" switch which not only prevents battery drain when the power output switch is turned off, but also prevents deep discharge of the battery and possible damage to the powered equipment when battery voltage drops below a preset value while the output switch is turned on and adequate voltage from the power line is unavailable. The sleep switch disables all of the power supply's circuitry save an input-deactivated driver transistor and a CMOS logic circuit required for both disabling and reawakening the circuitry. A one-shot awakening feature is triggered for approximately one second whenever the output power switch is closed. If the battery is adequately charged, the power supply remains awake; if not, it reverts to sleep. When connected to an adequate DC source, the unit functions as an on-line uninterruptible power supply; when disconnected, the computer becomes a battery-powered portable.

The design of a high efficiency, low voltage power supply using MOSFET synchronous rectification and current mode control

Abstract: The power supply described in this paper was developed for use in systems utilizing VHSIC integrated circuits which require voltages between two and three volts at substantial levels of current. The philosophy guiding this design, the pertinent trade-offs which were examined, and the data taken are presented.

Turbine-generator steady-state reactances

Abstract: The variation of the steady-state axis reactances of a 500 MW generator with load and power factor has been obtained from measured load points. At rated power, the direct axis reactance can be as much as 30% below the unsaturated value, and measured values of quadrature-axis reactance can vary by 20% over a range of power factors. The finite-element method has been used successfully to simulate the same load points. In these calculations, the absence of experimental error, and the ability of the method to show distributions of flux and saturation, have allowed a clearer insight into the complex phenomena that cause reactance variation. On load, the rotor body carries field leakage flux on the d-axis, and mutual flux displaced from it. These fluxes act together to give a saturation pattern about an intermediate axis. Thus, when current acts on one axis (d or q), flux is produced on both axes, although the cross-axis effect is only about one-tenth of the self effect. Each operating point may be described by effective values for the three conventional reactances (xd, xq and xa) used in a normal phasor diagram, or by six more basic reactances (three self- and three cross-axis reactances), each of which is load dependent. The variation of these reactances with load angle, at 100% and 50% of rated power, has been calculated, and its significance is discussed.

Operation of a Fixed Capacitor-Thyristor Controlled Reactor (FC-TCR) Power Factor Compensator

Abstract: A fixed capacitor-thyristor controlled reactor (FC-TCR) type of power factor compensator with thyristor-controlled series R-L load is analysed using an approximate and also a more exact circuit. The variation of power and power factor before and after compensation is examined for both cases. It is shown that considerable power factor improvement can be achieved in the circuit for low values of load thyristor firing- angle. However, for higher values of firing-angle, any improvement is obtained at the expense of additional. power losses.

Electronic ballast with high power factor

Abstract: A source of 120 Volt/60 Hz power line voltage is full-wave-rectified and yields an unfiltered DC voltage pulsed at 120 Hz rate. This pulsed DC voltage is applied to an inverter of a type that must be triggered into oscillation. At the beginning of each of the DC voltage pulses, the inverter is triggered into oscillation; and at the end of each of the DC voltage pulses, the inverter ceases to oscillate frm lack of adequate voltage to sustain oscillation. The output of the inverter is a 30 kHz squarewave voltage amplitude modulated at the 120 Hz rate. Across the inverter output is connected a high-Q series L-C circuit resonant at about 30 kHz. A fluorescent lamp is connected in parallel with the tank capacitor of the L-C circuit. With is high-Q resonant L-C circuit series-excited and parallel-loaded, the instantaneous magnitude of the current drawn by the inverter is substantially proportional to the instantaneous magnitude of the DC voltage provided; which implies that power is drawn from the power line with a relatively high power factor.

Method and apparatus for optimizing power consumption in an electrostatic precipitator

Abstract: A process for optimizing the power consumption of electrostatic precipitators communicating with a boiler or the like includes a load indexed signal fed forward to a field power controller to approximate the required power levels. An optical transducer is provided in the boiler stack for monitoring the emissions therefrom and feeds back a signal to the controller proportional to the emission from the stack to trim the power level. The controller incrementally adjusts the field power by comparing the opacity generated signal to a continuously optimized limit in order to thereby optimize the power consumption by lowering and raising the field power in response to changes in the opacity. The measurement of power permits the process to be extended to include supervision of electrode cleaning, compensation for fields out of service and flow balancing.

A Direct Method for Identifying the Optimal Power Factor Correction in Nonsinusoidal Systems

Abstract: This paper presents a new method employing the Golden Section search algorithm to determining the capacitor value for optimal power factor correction in a nonsinusoidal system. The major attribute of the method is that it, unlike conventional approaches, guarantees convergence to the optimal solution. This accomplishment is a direct result from the improvement in (1) the algorithm in which provisions are made to identify and to avoid capacitor values which would create resonant conditions, and (2) the problem formulation in which the effect of the transmission line impedance on the load voltage is included while calculating the optimal capacitor value. Finally, the contribution of the newly developed method is demonstrated in examples taken from previous publications.

Electroluminescent display drive circuitry

Abstract: An electroluminescent display drive circuit which compensates for the decrease in capacitance of the electroluminescent display panel that is experienced as the panel ages; this is accomplished by use of an RC time constant which will effectively increase the voltage presented across the electroluminescent display panel as the capacitive element of the RC time constant decreases with the age of the panel. Also presented is high frequency power supply to excite electroluminescent displays without a transformer such that the voltage across the display is in phase with the current through the display thereby reducing the effect of power factor and electromagnetic interference.

A Sinusoidal Pulsewidth Modulated Three-Phase AC to DC Converter-Fed DC Motor Drive

Abstract: The external performances such as power factor, displacement factor, harmonic factor, and ripple factor of a three-phase ac to dc converter-fed separately excited dc motor drive employing sinusoidal pulsewidth modulation (SPWM) control technique are obtained for different speeds and modulation indexes. Since separately excited dc motors with armature voltage control provide constant torque operation, the external performance is also determined for the drive motor operating at different values of constant load torque. Motoring and regenerating operations of the dc drive machine are considered. The three-phase PWM converter-motor drive system is analyzed, taking commutation effects into account in motoring and regenerating operations. The analysis has revealed 27 common modes in one repetitive period of the output voltage. The sequence of modes for all pulses in one period of the output voltage is established. Experimental oscillograms of typical waveforms from a laboratory-sized dc motor are illustrated to verify the basic principles of operation. Although the converter circuit requires some additional components in comparison with the commonly used phase-controlled converter, the improved performance characteristics make it attractive for industrial applications involving large power ratings.

Control circuit for diode-or connected power supplies

Abstract: A control circuit which monitors the output voltage of multiple power supplies connected to each other in a diode-or arrangement. When one power supply provides a higher voltage than the others the control circuit causes the lower output power supplies to operate in a standby mode. The control circuit includes voltage dividers on both sides of the output diode of the power supplies. These voltage dividers provide indications of the voltage output of their associated power supply and the other power supplies. A voltage comparator monitors the output voltage of its associated power supply and the other diode-or connected power supplies as indicated by the voltage dividers. The voltage comparator to adjust the voltage output of the associated power supply to a level just below the high output power supply, thereby leaving it in a standby mode of operation. If the high output power supply provides a reduced level of output voltage the voltage comparator in the standby power supply causes that power supply to then supply power to the load without any interruption in supply of the power.

Shutdown circuit for blocking oscillator power supply

Abstract: A protective circuit arrangement is provided for shutting down a power supply at the occurrence of a fault condition. The circuit arrangement allows current limiting in a switching transistor during a power on and/or power off cycle, but shuts down the power supply if current limiting occurs at any other time.

Tap switching protection circuit

Abstract: A protection circuit is provided for a tap switching line voltage regulator of the type which selectively switches in one of a predetermined number of taps on a winding of a transformer. The selective switching of the taps is controlled in response to the sensed load voltage to provide a regulated voltage to a load in the presence of a varying input line voltage. The tap switching line voltage regulator in response to the sensed load voltage controls the conductive state of a solid state series switching element in each of the switched tap lines. The protection circuit provides current limiting inductors in series with each of the solid state switching elements with all the inductors being wound on a common magnetic core. When switching from one tap to another tap, the tap switching line volage regulator in response to the sensed voltage operates to select an adjacent tap to the tap currently selected. Thus, tap switching proceeds in a sequential fashion up and down along the taps. The series inductors are wound on the common magnetic core such that the direction of the windings alternates between adjacent taps. Accordingly, the protection circuit provides a current limiting impedance to circulating currents that is four times the impedance to normal load currents. Accordingly, the circulating current caused by leading or lagging power factor operation is limited to prevent damage to the solid state switching elements.

Transistorized power supplies for induction heating

Abstract: In the last five years power MOSFETS have become available which have good radio frequency capability, low drive power requirements and ease of paralleling for higher power output. An induction heating power supply using power MOSFETS as switches is more efficient, is more easily controllable and has a lower capital cost than a valve supply, and the MOSFET power supply is not limited in frequency as thyristor supplies are. This paper gives details of three different types of transistorized power supplies developed for induction heating applications and compares their performances.