Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains iv, 116 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 66).

Report (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaf 59). Also available via the Internet

M.Ing. (Electrical And Electronic Engineering) / The theme of this thesis is the time compression of energy in electrical systems with the aim of improving the efficiency and average power throughput capability of existing pulse compression systems. Recent success in the design of pulse lasers indicated successful operation at repetition rates of up to 2kHz, demanding more powerful pulse power supplies. These pulse lasers require unusually high peak power, not obtainable with conventional switching techniques. Typical pulse voltages of up to 40kV with peak currents of lOkA and rise times of 150ns are required. Traditionally thyratrons have been used for this application, but the limited lifetime of these devices is a major shortcoming, especially when operating at 2kHz. New switching techniques were needed. Excellent results have been obtained using saturable inductors as magnetic switches in pulse compressors, but notwithout limitations. The generation of heat due to core losses tends to limit the power throughput capability of these compressors, especially in the final stages. The minimisation of these losses is therefore of utmost importance. In order to improve the current systems, a study of the basic principles of compression was conducted. Loss-mechanisms, especially in the magnetic components, were modelled with the object of minimising losses. The limitations imposed on the system by flux conservation in magnetic and dielectric materials, led to the development of the new concept of bipolar compression. A full-scale bipolar compressor and pulse power supply was constructed and experimental results on this system are presented, showing an improvement in the efficiency. A new method for designing pulse compressors, incorporating core losses,evolved from this development

This thesis is concerned with the timing and coincidence circuitry which controls the operation of a time-sharing function generator and four-quadrant analog multiplier. The functions to be generated are fed into the computer in time sequence as voltage waveforms of short duration, A waveform is sampled at a particular value of the independent variable x and the resulting ordinate Ef is normalized with respect to the maximum function ordinate Em and multiplied by a reference voltage Er. The output of the multiplier is then a voltage which represents the expression EfEr/Em and this voltage is channeled through the computer. Multiplication is performed by the following method. Two voltages E₁ and E₂ are simultaneously applied to two identical linear networks whose response to unit voltage is N(t). The outputs are then E₁N(t) and E₂N(t). If, on comparing E₁N(t) with a reference voltage E₃, the second sweep E₂N(t) is clamped at the instant of equality, then N(t) = E₃/E₁ and the output is E = E₂N(t) = E₂E₃/E₁. The present proposal is to generate the functions optically. A function is graphed, photographed on 35 millimeter film, and mounted on the rim of a rotating disc. The optical system projects a narrow segment of the function onto a phototube and its output, biased for the zero level, follows the function ordinate in a strict voltage analog sense. The full abscissa scale is represented by a constant voltage and the input specifying the sampling point is some fraction of this full-scale voltage. In order that the sampling point x be independent of the velocity of the scanning disc the coincidence circuitry eliminates velocity as a variable in the selection of x. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The research assesses the value of forecast information in operating a hydro-electric project with a storage reservoir. The benefits are the increased hydro power production, when forecasts are available. The value of short term forecasts is determined by comparing results obtained with the use of one month ahead perfect predictions to those obtained without forecasts but a knowledge of the statistics of the possible flows. The benefits with perfect forecasts provide an upper limit to the benefits which could be obtained with actual less than perfect forecasts. The effects of generating capacity and flow patterns are also discussed. The operation of a hypothetical but typical project is modelled using stochastic dynamic programming. A simple model of streamflow is formulated based on the historical statistics ( means and deviations). The conclusions are: The inflow forecasts can improve the operational efficiency of the reservoir considerably because of the reduction in forecasting uncertainty. The maximum release constraints affect the additional expected values. The benefits from the forecasts increase as the discharge limits reduce. Flow predictions in the high flow season are most valuable when the runoff in that time period dominates the annual flow pattern. However flow predictions at other times of the year also have value. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

More-electric aircraft have been the focus of considerable development in recent years. Increased utilisation of electrical systems on-board the latest generation of aircraft has seen an increase in fuel efficiency, through improved electrical derivation from the gas turbine engine and weight savings from the replacement of mechanical and hydraulic transmission systems. The advancement of power electronic and DC breaker devices has led to the reconsideration of DC power distribution systems for standalone networks. Aircraft can benefit from this through the reduced transmission losses, improved controllability and intelligent networking.Through the use of a multiphase synchronous generator, connected to a diode rectifier, a standalone DC network capable of providing power with redundancy can be produced. The aim of this research project is to investigate the effects that phase number, connection topology and winding pitch have on the behaviour of an AC generator connected to a passive diode rectifier. This thesis develops the methodology for determining the number of phases and the topology of the generator. Static and dynamic modelling is conducted through the use of computer finite element modelling and circuit simulation. The dynamic circuit simulation model is configured using parameters obtained from experimental data. The experimental test-rig, which is constructed to be reconfigurable in phase number, connection topology and winding pitch, is used to validate the simulation and provide detailed results on the steady-state operation of the generator-rectifier system. Open-circuit faults are introduced to assess the fault tolerance of the system and the effects of the inherent phase redundancy on the generator performance.

M. Ing. / The overall purpose of this research project was to develop a proposed maintenance strategy for generator sets utilised in biogas applications. One specific biogas application, involving the use of landfill gas (LFG) to generate electrical energy, was the focal point of the research project. This is due to the fact that the author’s organisation is extensively involved with landfills and power generation through the use of LFG.

<p> This thesis deals with the construction of Free Lattices on various sets of generators, ranging from a set of unordered generators to a countable set of chains. It also considers sublattices of the structures presented.</p> / Thesis / Master of Science (MSc)

Deregulation of the electric utility industry has increased the need to monitor the state of powerplant equipment, such as critical generators and motors, to improve availability and reduce life cycle costs via condition-based maintenance. To achieve these goals, nondestructive condition assessment and diagnostic tests are necessary to evaluate the quality and condition of a machine?s stator winding insulation system. Periodic tests are generally conducted to monitor insulation aging, diagnose problems, or provide some assurance that the winding has a minimum level of electrical strength. The basic principles of insulation testing are presented herein, and the physical mechanisms that affect the current versus voltage response are described. A stator winding insulation model was developed based on this theoretical foundation for use in understanding and analyzing the macroscopic behavior of complex insulation phenomena. A comprehensive, controlled laboratory experiment was conducted on a set of stator coils that were deliberately manufactured with and without insulation defects. Specific defects were chosen to represent the types of insulation problems typically encountered during manufacture or as a result of in-service aging, and included lack of resin cure, loosely-applied insulating tapes, internal conductive contamination, reduced density of the groundwall insulation, and thermal cycling damage. Results are presented from a series of electrical tests conducted on the coil specimens to compare the effectiveness of various test methods in detecting the different insulation problems. The tests included insulation resistance, polarization index, ramped direct voltage, dissipation factor, dielectric spectroscopy, partial discharge, and recovery voltage measurements. Dielectric principles and testing experience obtained during this investigation were applied to a collection of test results obtained by the author from in-service machines during the past ten years. These results and analyses provide a practical illustration of the ability of the ramped direct high-voltage test method to distinguish between normal insulation and that with problems, and to help identify the cause and extent of the deficiencies. While no single diagnostic method is ideally suited to detect all possible stator winding insulation problems, ramped voltage tests are shown to be useful in determining when corrective actions are needed and what the appropriate actions are.

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