# Programa de Pós-graduação em Engenharia Elétrica e da Computação

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### Navegando Programa de Pós-graduação em Engenharia Elétrica e da Computação por Por Orientador "ALVARENGA, Bernardo Pinheiro de"

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Item Aplicação do mapeamento conforme no cálculo do fator de Carter(Universidade Federal de Goiás, 2008-06-06) CALIXTO, Wesley Pacheco; BRITO, Leonardo da Cunha; http://lattes.cnpq.br/6660680440182900; ALVARENGA, Bernardo Pinheiro de; http://lattes.cnpq.br/9850449311607643Mostrar mais The present work proposes a numeric formulation for the determination of Carter's factor as a function of the geometry of the slot of electric machines. This task is made by the use of the Schwarz-Christoffel transformation. In order to reach the objective, there is the need to calculate the Schwarz-Christoffel inverse transformation. This represents a non-linear optimization problem. Therefore, it is proposed a methodology to calculate the parameters of the Schwarz-Christoffel inverse transformation using genetic algorithms. The assessment of Carter s factor is achieved considering polygonal domains with many vertices. The transformation leads to a rectangular domain approach. Moreover, some case studies are proposed and the methodology results are compared to traditional formulation results for the Carter s factor, yielding some disparities.Mostrar mais Item Controle Fuzzy e acionamento a velocidade variável de sistema resfriador de leite(Universidade Federal de Goiás, 2010-06-17) CHAVES, Eric Nery; ALVARENGA, Bernardo Pinheiro de; http://lattes.cnpq.br/9850449311607643Mostrar mais This work presents the application of control techniques to drive single-phase induction motors with the aim of improving the performance of cooling systems. The control system is based on Fuzzy Logic and is applied to a three-phase PWM inverter adapted to drive singlephase motors with volts per hertz technique. The main feature of the work is to control the temperature of the cooling system driven by a hermetic compressor using variable speed. A commercial milk cooling system is used to obtain the results.Mostrar mais Item Operação do gerador de indução em conexão assíncrona com a rede monofásica(Universidade Federal de Goiás, 2010-03-26) LIMA, Nelio Neves; ALVARENGA, Bernardo Pinheiro de; http://lattes.cnpq.br/9850449311607643Mostrar mais This text reports the effort to present a proposal of a power generation system based on cage rotor Induction Electrical Machine associated to a sinusoidally-switched PWM (Pulse Width Modulation) frequency converter responsible for maintaining constant 60 Hz frequency at the generator leads. DC side at the PWM converter is nonsynchronously connected to a single-phase utility line by means of a full-bridge current-fed thyristor inverter, employing a step-down DC-DC converter in order to turn the grid injected current into a sinusoidal waveform. The proposed system allows for the operation as cogenerator in sites fed by single-phase utility net where there is availability of energetic resources. The DC capacitor voltage (Vdc) is controlled through the DC side energy balance adjusting the amplitude of the active current sent to the utility grid. The control strategy employed was the analogic proportional-integral (PI) error compensation. The system is also able to act as reactive power compensator to the AC loads as the Cdc capacitor represents a voltage source to the inverter and the three-phase diode bridge allows for bidirectional power flow between AC and DC sides. Simulation and experimental results has corroborated system viability to provide three-phase balanced regulated voltages complying with ANEEL 505/2001 Resolution and with IEEE Std 519-1992.Mostrar mais Item Avaliação dos Impactos da Impedância de Falta e da Geração Distribuída em Estudos de Afundamentos de Tensão(Universidade Federal de Goiás, 2009-09-21) RAMOS, Alessandro Candido Lopes; LEBORGNE, Roberto Chouhy; http://lattes.cnpq.br/3938003534716565; ALVARENGA, Bernardo Pinheiro de; http://lattes.cnpq.br/9850449311607643Mostrar mais This work presents an impact analysis of the fault impedance and distributed ge- neration on the amplitude and annual average quantity of voltage sags in sensitive end-users. Phase-to-ground solid and non-solid faults were simulated in 62 transmission lines at 230, 138, 69 and 13.8 kV, which made part of the electrical system of the municipality of Goiânia, the capital city of the Goiás State, Brazil. For each fault position, a resistive fault impedance was considered. This impedance was considered equal to 0, 2, 5, 10, or 15 or even random. In this case, each one of the mentioned impedance values has a specific probability to occur. The voltage-behind-reactance synchronous machine model was used to model the distributed generation units. The analysis here described is based on simulation results obtained through the Fault Position Method in combination with the Monte Carlo Method. The faults were si-mulated through a frequency-domain fault simulation software called ANAFAS. In order to overcome some limitations and increase the flexibility of the simulation tool, a computational program, called ANAFAS-GUI, was developed in Java language. This program allows the automatic simulation of several cases, with different fault characteristics, by running ANAFAS in background mode. The Monte Carlo Method was implemented in MATLAB. Thus, an efficient computational tool has resulted from the combination of the developed computational tools for the purposes of this work. The main simulation results are the tenden-cy and probability density curves of the voltage sags and their classes. From the results it can be concluded that, if the fault impedance is considered as being a random variable, then the predict voltage sags quantity and severity at the sensitive end-user bus are more accurate when compared to the cases in which this impedance is not considered as such. It can also be concluded that, the connection of a distributed generation unit next to the sensitive end-user bus may result in a decreasing of the voltage sags quantity and severity at this bus, depending on the rated power of the unitMostrar mais Item PROJETO, IMPLEMENTAÇÃO E AUTOMAÇÃO DE UMA BANCADA PARA ENSAIOS DE MOTORES A RELUTÂNCIA CHAVEADOS(Universidade Federal de Goiás, 2009-06-30) TEIXEIRA, Weldon Carlos Elias; ALVARENGA, Bernardo Pinheiro de; http://lattes.cnpq.br/9850449311607643Mostrar mais This work presents a proposal for testing Switched Reluctance Motors, which is feasible by the design and construction of an automated test bench. The test proposal intends to measure phase s resistance; to compute copper loss; to obtain the magnetizing curves for aligned and unaligned rotor and a performance test, which is based on fixing the under test motor rotor speed by a drive machine that is drove by a frequency inverter. The computational automation is restricted in changing the d.c. voltage applied to the under test switched reluctance motor by a programmable sinusoidal voltage source; changing and/or fixing the under test rotation speed of the switched reluctance; changing the semiconductor-switch switching angle; acquisition and processing of the data obtained in the tests. Computational simulations were performed for validating tests results made in an available switched reluctance motorMostrar mais