The lithium disilicate (LS2) glass system provides the basis for a large number of useful glass-ceramic products. Microwave processing of materials such as glass-ceramics offers unique benefits over conventional processing techniques. Variable frequency microwave (VFM) processing is an advanced processing technique developed to overcome the hot spot and the arcing problems in microwave processing. In general, two main questions are addressed in this dissertation: 1. How does microwave energy couple with a ceramic material to create heat? and, 2. Is there a "microwave effect" and if so what are the possible explanations for the existence of that effect? The results of the present study show that VFM processing was successfully used to crystallize LS2 glass at a frequency other than 2.45 GHz and without the aid of other forms of energy (hybrid heating). Crystallization of LS2 glass using VFM heating occurred in a significantly shorter time and at a lower temperature as compared to conventional heating. Furthermore, the crystallization mechanism of LS2 glass in VFM heating was not exactly the same as in conventional heating. Although LS2 crystal phase (Orthorhombic Ccc2) was developed in the VFM crystallized samples as well as in the conventionally crystallized samples as x-ray diffraction (XRD) confirmed, the structural units of SiO4 tetrahedra (Q species) in the VFM crystallized samples were slightly different than the ones in conventionally crystallized samples as the Raman spectroscopy revealed. Moreover, the observed reduction in the crystallization time and apparent temperature in addition to the different crystallization mechanism observed in the VFM process both provided experimental evidence to support the presence of the microwave effect in the LS2 crystallization process. Also, the molecular orbital model was successfully used to predict the microwave absorption in LS2 glass and glass-ceramic. This model was consistent with experiments and indicated that microwave-material interactions were highly dependent on the structure of the material. Finally, a correlation between the Fourier transform infrared reflectance spectroscopy (FTIRRS) peak intensities and the volume fraction of crystals in partially crystallized LS2 glass samples was established. / Ph. D.

This thesis focuses on the study, implementation and improvement of a digital Generator Control Unit (GCU) for a high-speed synchronous brushless generator. The control of variable frequency power system, a preferred candidate in More Electric Aircraft (MEA), becomes a big challenge. Compared with conventional analog GCU, digital GCU is a future trend due to the properties such as easy tuning, modification and no aging. Control approaches adopted in the new GCU design is introduced. It has multiloop structure and model-based characteristics. Sensorless rotor position detection was used to finish Park transformation. DSP+FPGA based controller hardware was developed in the lab. A set of hardware was designed to implement the control algorithms. VHDL-based software was developed for FPGA, which is working as a bridge between DSP and peripheral circuits. C-based software was designed to implement control algorithm inside DSP. A testbed system was developed according to the lab capacity of CPES. The complete load transit responses were tested according to the standard ISO1540 and EN8420. Good match between simulation and experiment has been reached. Compared with benchmark controller, great improvement in both steady state and dynamic performance is realized. A feasibility of using digital GCU in the next generation aircraft has been proved preliminarily. However, the challenge of reliability issues in digital system and software still needs further attention. / Master of Science

Este trabalho avalia a aplicação de inversores de freqüência realizada em estações elevatórias de água tratada da cidade de São José dos Campos que são monitoradas pelo Centro de Controle Operacional da Sabesp. Foram estudadas as características técnicas de quatro sistemas de bombeamento que operam com velocidade variável. O trabalho apresenta uma proposta de metodologia para a seleção de inversores de freqüência, com base na metodologia recomendada pelo EUROPUMP e HYDRAULIC INSTITUTE (2004) aplicada em quatro sistemas da cidade de São José dos Campos. Essa proposta de metodologia foi executada através da avaliação seqüencial de um fluxograma e da análise gráfica das informações instantâneas e históricas dos parâmetros de vazão, pressão e freqüência de rotação, existentes no banco de dados dos servidores de supervisão e controle do Centro de Controle Operacional de São José dos Campos. Após a aplicação dessa metodologia, conclui-se que, a aplicação de inversores de freqüência nos sistemas estudados estava adequada e recomenda-se a sua aplicação em sistemas de bombeamento semelhantes. / The main purpose of this work is to evaluate the application of Variable Frequency Drives ? VFD, carried out in water pumping stations managed by SABESP ? Companhia de Saneamento Básico do Estado de São Paulo, located in the city of Sâo José dos Campos that are monitored by the Operational Control Center ? O.C.C. Technical characteristics of four pumping systems were studied, mainly those operating with fixed or changeable speed. It proposes a new methodology for VFD selection, based on the methodology recommended by EUROPUMP and HYDRAULIC INSTITUTE (2004), used on the systems mentioned before. This proposal of methodology were done using instantaneous and historical information of flow, pressure and rotation frequency parameters stored on data base installed on supervision and control servers installed. After this application, we also concluded that the use of VFD on the evaluated systems was correct and through this we recommend its use on similar pumping systems.

Abstract: This paper presents the results of an experimental investigation into the application of inverter-based variable speed drives to positive displacement rotary compressors. Designs and implements a DSP-microprocessor based of an inverter drive for high-efficiency compressor used in air conditioner. We control the compressor with sine PWM and V/F scheme. Permanent magnet synchronous motor has potential for energy saving in general applications on compressor drives. Permanent magnet synchronous motor drives are used for applications like compressors¡Awhere high dynamic performance is not a demand¡Asimple V/F control strategies may be sufficient to obtain the required control performance. For energy saving to find the best control strategy for an inverter drive for high efficiency compressor used in air conditioner.

The analysis of the feature and application of linear induction motors at work have been performed; mathematical models of linear motors have been studied; mathematical description of induction machine have been presented; coordinate transform have been studied; dynamic equations in moving and move-less systems of axes of linear induction motor have been presented; the analysis of the classification of induction drives control modes have been performed. Four models of the frequency-regulated electric drives with linear induction motors have been studied: when the motor is supplied from variable frequency mains supply, when the motor is supplied from frequency converter, when frequency is changed by program, when frequency is changed in close-loop by vector control system. The characteristics of those models have been compared and performed. The received results are summarized in the conclusions.

In this thesis, a new approach for single-stage power factor correction converters is proposed to increase their power ratings to be in the multiple kilowatts levels. The proposed techniques are based on the utilization of modified three-level resonant converter topologies. These topologies provide low component stresses, high frequency operation, zero voltage switching, applicability under a wide range of input and output conditions as well as added control flexibility. The proposed control algorithms are based on a combination of variable frequency and asymmetrical pulse width modulation control or variable frequency and phase shift modulation control. In either case, the variable frequency control is used to tightly regulate the output voltage, whereas, pulse width or phase shift modulation is used to regulate the dc-bus voltage as well as the input power factor. New converter topologies, their operation and steady state and dynamic analyses are presented in details. A modelling approach based on average multiple frequency methods is also proposed. This approach leads to the development of a full order state space model with the two control variables explicitly separated allowing a better controller design. The model can be used either at high level of detail expressing the non-linearities of the system or it can readily be simplified to a linear decoupled model for approximate solutions. Finally, a discrete time controller for the proposed converters, which is suitable for FPGA implementation, is presented. Analytical, simulation and experimental results are provided to verify the proposed concepts. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2008-01-30 14:28:15.725

Variable frequency drives (VFD) and subsea (umbilical) cables are frequently used in electrical submersible pump (ESP) systems for offshore platforms. There are two basic system configurations for ESP systems; VFD can be installed on the platform and the motor is connected to it through an umbilical cable, and VFD and the motor are installed closely and they are connected to the system through an umbilical cable. In this thesis, the pros and cons of each configuration are mentioned, but the focus is on the system with a VFD controlled motor through a long umbilical cable. A 36-pulse VFD is studied. Since multilevel VFDs have high frequency harmonics, high frequency modeling of the umbilical cable is used, and skin effect is also taken into consideration in the cable. The effect of the interactions between the umbilical cable and high frequency harmonics on the motor terminal voltage is explored.

This study incorporates the potential use of Variable Frequency Drives on various motors as well as areas of improved heat transfer in an older, mid-sized coal fired power plant. In power plants, fluid flow rates are often controlled using dampers or valves while the motors that power the pumps stay at full speed resulting in a significant amount of wasted electrical power; energy is also lost due to poor heat recovery prior to gases leaving the system. By examining pump usage as well as additional heat available for recovery, potential energy savings will be determined. Preliminary results of five motors suggested for variable frequency drive application show annual savings that total 31.1 GWh, resulting in a 1.66% increase in overall plant efficiency. Total project costs are near $2 million resulting in a simple payback period of less than two years assuming 0.04 $/kWh. For every degree reduction of the flue gas temperature by means of heat recovery that is reused elsewhere in the cycle, 2 Billion BTU of coal would be saved annually. One realistic scenario suggested heat recovery resulting in a 120°F degree reduction of flue gas temperature amounting to a 2.54% increase in cycle efficiency.

Este trabalho avalia a aplicação de inversores de freqüência realizada em estações elevatórias de água tratada da cidade de São José dos Campos que são monitoradas pelo Centro de Controle Operacional da Sabesp. Foram estudadas as características técnicas de quatro sistemas de bombeamento que operam com velocidade variável. O trabalho apresenta uma proposta de metodologia para a seleção de inversores de freqüência, com base na metodologia recomendada pelo EUROPUMP e HYDRAULIC INSTITUTE (2004) aplicada em quatro sistemas da cidade de São José dos Campos. Essa proposta de metodologia foi executada através da avaliação seqüencial de um fluxograma e da análise gráfica das informações instantâneas e históricas dos parâmetros de vazão, pressão e freqüência de rotação, existentes no banco de dados dos servidores de supervisão e controle do Centro de Controle Operacional de São José dos Campos. Após a aplicação dessa metodologia, conclui-se que, a aplicação de inversores de freqüência nos sistemas estudados estava adequada e recomenda-se a sua aplicação em sistemas de bombeamento semelhantes. / The main purpose of this work is to evaluate the application of Variable Frequency Drives ? VFD, carried out in water pumping stations managed by SABESP ? Companhia de Saneamento Básico do Estado de São Paulo, located in the city of Sâo José dos Campos that are monitored by the Operational Control Center ? O.C.C. Technical characteristics of four pumping systems were studied, mainly those operating with fixed or changeable speed. It proposes a new methodology for VFD selection, based on the methodology recommended by EUROPUMP and HYDRAULIC INSTITUTE (2004), used on the systems mentioned before. This proposal of methodology were done using instantaneous and historical information of flow, pressure and rotation frequency parameters stored on data base installed on supervision and control servers installed. After this application, we also concluded that the use of VFD on the evaluated systems was correct and through this we recommend its use on similar pumping systems.

Made available in DSpace on 2014-07-29T14:52:05Z (GMT). No. of bitstreams: 1 Tese Antonio Marcos 25022010.pdf: 1893079 bytes, checksum: 7678a19648ddfd55dd2c6b7a3ecaa4fd (MD5) Previous issue date: 2010-02-26 / It has been noticed lately that some regions of Brazil has presented lower supplying of water and energy. It has occurred mainly during the period of the year when it is higher the need for irrigation water. It is necessary to recognize the possibility of negative impacts of irrigation, to analyze them and present solutions so as to improve the irrigation systems. The aim of this study is the estimation by one system of irrigating the central pivot, breaking from the characteristics of this systems and considering the analyzed of varies combinations of pipes for water main and lateral line, choice of the set motor pump with major yield, utilization and comparison among motor standard and of high yield after the selection from best option in diameter from water main and lateral line, analyze the system using a variable frequency drives. The result with the calculations performed was an energy saving of 25% considering the use of the diameter for the two economic systems adopted. For analysis using a frequency inverter with resulted in a saving of 9.23% for center pivot irrigation system exists, and for the new center pivot irrigation system resulted in savings of 10.6%. The analysis of return on investment considering the use of the system with variable frequency drive was a rate of return on investment of 6.52% pa, center pivot irrigation system for existing and center pivot irrigation system was again 9.48 % pa. The project's return, more long-term, or feasible in the short term, considering the benchmark interest rate to 12.25% pa. The results presented in the study show that there is great potential for power savings, and economic analysis showed the feasibility of the system with return on invested capital. The calculation used for determining the center pivot irrigation system reduces the cost and time to obtain data that make analysis of the potential of saving electricity. / Ultimamente vem percebendo com mais intensidade, a escassez de água e energia elétrica em algumas regiões do país. Esta observação ocorreu justamente no período do ano quando existe a maior necessidade de demanda de água das culturas irrigadas. A necessidade de reconhecer a possibilidade de ocorrência de impactos negativos do uso da irrigação, avaliando-os e desenvolvendo soluções tecnológicas que provoquem melhorias, viabilizando a atividade agrícola irrigada, de forma adequada. Este trabalho teve por objetivo a otimização de um sistema de irrigação pivô central, partindo das características desse sistema e considerando a análise de várias combinações de tubos para a adutora e linha lateral; escolha do conjunto motobomba com maior rendimento; utilização e comparação entre motor padrão e de alto rendimento, após a escolha da melhor opção de diâmetro da adutora e linha lateral, aná lise do sistema utilizando inversor de frequência. A metodologia adotada consistiu na otimização de dois sistemas de irrigação pivô central um existente no local e outro considerando um sistema de irrigação pivô central novo projetado para atender determinada lamina d água. Para os dois sistema de irrigação pivô central foi considerando a análise econômica do diâmetro das tubulações que compõem o sistema de irrigação a pivô central, analisando varias configurações de diâmetros diferentes, rotações do conjunto moto bomba, utilização de motores de alto rendimento e padrão, uso do inversor de freqüência. O resultado com os cálculos realizados foi uma economia de energia elétrica de 25% considerando o uso do diâmetro econômico para os dois sistemas adotados. Para análise com uso inversor de frequência com, resultou em uma economia de 9,23% para o sistema de irrigação pivô central existente, e para o novo sistema de irrigação pivô central resultou em uma economia de 10,6%. A análise do retorno do investimento considerando o uso do sistema com inversor de frequência foi de uma taxa de retorno do investimento de 6,52% a.a, sistema de irrigação pivô central existente e para o sistema de irrigação pivô central novo foi de 9,48% a.a. O projeto tem retorno, mas de longo prazo, ou seja, inviável em curto prazo, considerando a taxa básica de juro com 12,25% a.a. Os resultados apresentados no trabalho mostram que há um grande potencial de economia de energia elétrica, e a análise econômica mostrou a viabilidade do sistema com retorno do capital investido. O cálculo utilizado para a determinação do sistema de irrigação pivô central diminui o custo e o tempo para obtenção de dados que compõem a análise do potencial de economia de energia elétrica.