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In this work it is presented an energy harvesting system based on disperse magnetic energy produced by electric current across power line of a power distribution network in order to supply energy for devices in a wireless sensor network. The system is based on toroidal cores tested and validated with different materials and dimensions (five based on ferrite, seven based on nanocrystalline, three based on iron powder) aiming harvesting optimal power device. From principles of magnetic ferromagnetic materials, it is discussed the magnetic field theory to obtain energy for supplying power to devices. It was implemented a prototype consisting of a test bench capable of emulating power-line high currents and of a power conditioning circuit. Test procedures were executed in three parts. The first was to determine the magnetic parameters (e.g. relative permeability and magnetic curve) of each harvester using a circuit able to measure core permeability in order to obtain B x H cycle. The second was to test a proposed power conditioning circuit composed of an AC/DC rectifier and a voltage regulator. The third, the experimental results were compared with theoretical ones. The obtained experimental results have been in agreement with theory, showing that the energy harvesting system is capable of supplying up to 315.6 mW from ferrite based core, 54mW from nanocrystalline based cores and 0.77mW from iron powder based ones, by capturing magnetic dispersion produced by a 15A current in the power line, which can be applied to various low power devices, mainly in wireless sensor network for data acquisition and control parameters of the power line itself ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES ; Neste trabalho é apresentado um sistema de captação de energia por dispersão magnética produzida pela corrente elétrica em uma linha de potência de uma rede de distribuição de energia, para alimentação de dispositivos de uma rede de sensores sem fio. Esse sistema é baseado em núcleos toroidais testados e ...

This work presents a study of the behavior of a nanocrystalline core with toroidal shape based on experimental data where a mathematical model basic on hyperbolic tangent and Maxwell's equations is used, and is demonstrated useful and able to characterize the parameters of the nonlinear magnetic core with some level of precision. The model presented was run on Matlab software, which is needed to introduce the core properties to predict the characteristics of the desired energy harvester considering a specified power. The resulted computational tool can be used to determine the behavior of magnetic and electrical parameters of the core. The obtained simulations were compared with experimental results to validate the modeling used. ; Neste trabalho é apresentada uma pesquisa sobre o comportamento de um núcleo nanocristalino com forma toroidal, com base em dados experimentais. Sendo realizada a partir do estudo de um modelo matemático utilizando a tangente hiperbólica e as equações de Maxwell, que demostra ser útil e capaz de caracterizar os parâmetros de um núcleo magnético não linear com aproximações. O modelo apresentado foi implementado no software Matlab, em que é necessário introduzir as propriedades do núcleo para prever as características de um dispositivo captador de energia com uma potência desejada. A ferramenta computacional implementada pode determinar o comportamento das grandezas magnéticas e elétricas do núcleo. As simulações obtidas foram comparadas com resultados experimentais a fim de validar a modelagem utilizada.

In this dissertation we present the main results about the magnetic properties of elastic ferromagnets based on the analysis of different behaviours of the exchange parameter O (or exchange interaction). Firstly, we analyzed the variation of exchange parameter O with H and T , i.e., O vH w , O vT w and O vH,T w , obtaining an additional contribution whitout defined physically origin, vH,T w adic { ´S , which when added to the conventional entropy, conv { ´S , results in the variation of total entropy, total { ´S , obtained by Maxwell¡¦s relation. In what follows, we implement a model that includes a vibrational energy in the Einstein approximation for high temperatures, and an other with a quadratic dependence of the isothermal compressibility with the temperature by means of the relation 2 o T K ­ K y a T , so that obtain an additional contribution with defined physically origin. These additional contributions are obtained by magnetoelastic coupling to rewrite the system in terms of the exchange parameter O x that when applied to the model entropy exchange (proposal by Plaza-Campoy), leads to additional contributions to the { ´S eT curves. In a third approximation, we formulate the O parameter within the RKKY fenomenology, Ë Í o RKKY O ­ O J ç , and analyse the magnetic properties (magnetization, exchange parameter, deformation, magnetic entropy, etc.) for different regions of the RKKY curve. In this fenomenology, the exchange parameter varies in a non linear form as a function of the deformation, although when we get closer to a linear region we verified that the Bean- Rodbell model approximates well the RKKY model. Finally, we start from a generalized exchange Hamiltonian and formulate an generalized exchange energy that inserted in the Gibbs free energy, promotes an additional contribution to the magnetic properties, showing up the importance of the v1 4 w factor in the exchange hamiltonian when the exchange parameter depends on the interatomic distances. ; Nesta dissertacao sao apresentados os principais ...

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; CNPq: 131180/2014-2 ; Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE ; Maçãs são consideradas fonte de compostos fenólicos e representam uma das culturas economicamente mais importantes e consumidas no mundo. Por serem fontes de monossacarídeos, minerais e fibras dietéticas são parte importante da dieta humana, e o hábito de comê-las traz benefícios à saúde. Alimentos com alto teor de umidade, como as frutas, deterioram-se em períodos curtos, fazendo com que o emprego de técnicas de conservação, como a secagem, seja fundamental para a cadeia de produção. No entanto, a secagem exige um consumo intenso de energia e pode causar danos indesejáveis aos parâmetros de qualidade dos produtos, devido à temperaturas altas e longos tempos de exposição do produto ao ar de secagem. Uma alternativa para redução do gasto energético é a secagem intermitente, na qual as condições de operação são alteradas com o tempo. Com o intuito de avaliar os efeitos da aplicação da intermitência na secagem convectiva de fatias de maçã Fuji sobre parâmetros de qualidade física (textura, densidade, atividade de água e cor) e nutricional (retenção de ácido clorogênico), cinética de secagem e correspondente consumo de energia, foram comparadas amostras e tratamentos de secagens contínuas e intermitentes. Para isso, foram avaliadas 7 configurações de secagem intermitente feitas em dois estágios, o primeiro com três níveis de temperatura (95, 85 e 75 °C) e de tempo (30, 45 e 60 minutos) e o segundo com três níveis de temperatura (50, 60 e 70 °C). Secagens contínuas foram conduzidas à temperatura do segundo estágio de secagem. O consumo de energia foi mensurado por um equipamento analisador e também calculado através de um balanço de energia, considerando o sistema adiabático. O conteúdo de ácido clorogênico nas amostras in natura e processadas foi acompanhado por espectroscopia de ressonância magnética nuclear de 1H pela análise das ressonâncias características de ...

In recent decades, the growing demand for miniaturized, portable and autonomous electronics has intensified the search for new and appropriate energy sources. Following this context, the purpose of this work is to develop an energy-autonomous electronic system, powered by magnetic energy harvesting. Being the energy harvesting system composed of an electromagnetic transducer, to capture and convert stray magnetic field around power lines, and an electronic circuit to condition the energy generated by the transducer and provide adequate power for a resistive load of low consumption. An experimental methodology was employed to select the appropriate material for the core of the transducer therefore been conducted many laboratory tests to analyze and compare the performance of the transducers with respect to power and power density provided by the transducers two ferromagnetic materials distinct, the Ferrite and Nanocrystalline Alloy (FeSiB). After analyzing the data, it is concluded that for this application the Nanocrystalline Alloy showed the best results in terms of power density, and therefore, was selected as the material of the toroidal core of the transducer. However, in the output of the secondary coil was observed high voltage peaks, so that could cause damage to electronic devices connected to the coil circuit. Therefore, it chose to divide the secondary coil into two coils, both connected in parallel to reduce the inductance, at end It is found the effectiveness of the solution, because, reduced voltage spikes and kept the magnitude of the effective tension. However, the showed transducer high inductive reactance, due to its physical parameters, in particular, the high permeability, to compensate were used capacitances connected in series with the coil, in order to define the ideal situation for the system provide maximum power for the load. The power conditioning circuit has been designed to power the wireless sensor node nRF24LE1 the Nordic semiconductors, therefore, have been designed a full-wave ...

Inthescientificliterature,energyharvestingtofeedsensornodeinwirelesssensornetworks can be accomplished in several ways: by magnetic induction, by temperature difference between surfaces (thermal energy), by displacement/movement devices (kinetic energy), and others. Some works with magnetic energy harvesters take advantage the magnetic field produced by the mains electrical current (60 Hz) to supply these sensor nodes, through the principle of magnetic induction. Part of these works neglects the effects of hysteresis or saturation in the device’s magnetic material, which can lead to lower energy harvesting efficiency. To increase the efficiency of these devices, in this work is presented a nonlinear model of the magnetic harvester, whose structure is similar to those used in current transformers (CTs). The material in which the core is formed is a nanocrystalline alloy with very high relative magnetic permeability (greater than 100,000), different from the conventional materials used and with high non-linearity. The flux density and magnetic field in the harvester are modeled using Maxwell’s equations. A nonlinear constitutive relation using the hyperbolic tangent function is applied to approximate the phenomena of hysteresisandsaturationintheCT.Fromtheequationsobtained,theoutputvoltageofthe CT can be calculated and expressed by nonlinear differential equations whose resolution is given by numerical computational methods. To solve such equations the MATLAB© software was used. Experimental data (voltage, secondary and primary currents) were collected for various harvesters changing their dimensions, the number of secondary turns and the primary electrical current levels. From these data the hysteresis loop of the CTs was extracted and their magnetic parameters (for example the coercive field strength and saturation magnetic flux density). In addition to the nanocrystalline alloys, toroidal ferrite cores were used to verify if the model can reproduce the operation of traditional magnetic materials used in CTs. Simulation and ...

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia O trabalho efetuado teve como objetivo primordial a realização de testes experimentais para a validação de um protótipo de um gerador síncrono de ímanes permanentes (PMSG)de seis fases.O projeto e conceção de equipamento de suporte por forma a permitir a aplicação de uma estratégia de controlo preditivo de corrente (PCC) e a execução de testes em laboratório para determinar os parâmetros do PMSG foram as principais tarefas executadas no âmbito do trabalho realizado. O Capítulo 1, de cariz introdutório, releva a necessidade do estudo de máquinas elétricas multifásicas. A aplicação, vantagens e diferentes configurações de acionamentos baseados em PMSG multifásicos encontram-se também descritos neste capítulo. A secção final deste capítulo sintetiza os objetivos pretendidos na realização do trabalho efetuado. O Capítulo 2, inclui uma revisão geral ao trabalho realizado previamente no estudo de PMSGs de seis fases. Os modelos matemáticos válidos para o controlo de PMSG de seis fases com diferentes variáveis de controlo são explicitados, sendo finalizado com uma revisão dos métodos de determinação de parâmetros em PMSGs de três e seis fases. No Capítulo 3 é realizada uma abordagem ao procedimento experimental efetuado. A montagem experimental utilizada é descrita e é feita uma análise aos resultados obtidos.O Capítulo 4 conclui o trabalho realizado, finalizando com tópicos de sugestão para trabalhos futuros. The main goal of this work is to execute experimental tests for the validation of the prototype of a six-phase permanent magnet synchronous generator (PMSG). The project and building of support hardware in order to run the prototype under a predictive current control (PCC) strategy and the determination of the PMSG parametersthrough the execution of experimental tests were the main tasks executed in this work. Chapter 1, of introductory nature, highlights the need to study multiphase electrical machines. The applications, advantages and different congurations of PMSG based electric drives are described in this chapter. The main tasks of this work are briefly stated at the end. Chapter 2, reviews the previous studies related to the six-phase PMSG. The mathematical models for six-phase PMSG with dierent control variables are included and the chapter is concluded with a revision of the parametrization methods available in the literature for three-phase and six-phase PMSGs. Chapter 3 mainly consists in an approach to the experimental procedure. The experimental setup is described and the experimental results are presented and analysed. Chapter 4 contains the main conclusions of this work, and some proposed subjects that can be addressed in future work, mainly in the parameterization of six-phase PMSG subject.

Dissertação de Mestrado, Engenharia Elétrica e Eletrónica, Especialização em Sistemas de Energia e Controlo, Instituto Superior de Engenharia, Universidade do Algarve, 2016 A conversão de energia elétrica a partir de fontes de energia renováveis tem vindo a aumentar. A energia das ondas é uma mais valia, uma vez que as ondas do mar apresentam uma elevada densidade energética. Nesta dissertação propõe-se um dispositivo capaz de aproveitar a energia das ondas para a conversão de energia elétrica, composto por um gerador linear acoplado a uma mola magnética. Para isso, foi necessário estudar alguns tipos de molas magnéticas existentes, efetuando simulações recorrendo a um programa de simulação de elementos finitos, o FEMM e ao MATLAB. Foi criado um modelo dinâmico do sistema, de maneira a simular o sistema boia-gerador em ambiente Simulink, analisando as suas respostas quando submetido a uma onda linear. De modo a ter uma ideia mais aprofundada do funcionamento da mola magnética, foi desenvolvido um banco de ensaio, que permitiu analisar a força que uma mola magnética consegue suportar em relação à distância total dos magnetos permanentes que constituem a mola magnética. The conversion of electricity from renewable energy sources has been increasing. Wave energy is an asset, since the waves have high energy density. This thesis proposes a device able to harness the energy of the waves for electric power conversion, composed of a linear generator coupled to a magnetic spring. For this purpose, we need to study several types of magnetic springs and to perform simulations using a simulation finite element program, the FEMM, and MATLAB. A dynamic model system was created, in order to simulate the float-generator system in Simulink, and to analyse its responses when subjected to a linear wave. In order to have a more detailed view of the operation of the magnetic spring, a test bench has been developed, which allowed analysing the force that a magnetic spring can withstand in relation to the total distance between the permanent magnets that constitute the magnetic spring.

Wind generators have recurring operating interruptions due to internal failures. Internal failures are difficult to detect and may silently lead to machine damages since they occur between turns, being named turn-to-turn, or between turn and machine housing, being named turn-to-ground. Thus, these plants must be constantly monitored so that these faults are detected in their initial stage. This early detection makes it possible to reduce maintenance costs while decreasing wind turbine downtime. This work proposes a strategy for noninvasive detecting stator failures in its initial stage through a classifier module that analyzes the stator current patterns. This classifier is based on a Multilayer Perceptron (MLP), that is a class of feedforward artificial neural network (ANN), which was trained using a dataset generated by a mathematical model of the PMSG-based wind turbine. The results show that the MLP classifier is able to detect the proposed problem with 97.62% global accuracy. In addition, detection was performed at a initial stage of 1% to 4% of faulty turns with 100% accuracy, contributing to continuous and noninvasive detection of internal wind turbine stator faults. ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES ; Os geradores eólicos apresentam interrupções de operação recorrentes devido à ocorrência de falhas internas. Falhas internas são de difícil detecção e que podem conduzir, silenciosamente, a danos na máquina e podem ocorrer entre as espiras, sendo denominadas espira-espira, ou entre espiras e a carcaça da máquina, sendo denominadas espira-terra. Assim, estas plantas devem ser constantemente monitoradas para que essas falhas sejam detectadas em seu estágio inicial. Essa detecção precoce possibilita a redução do custo de manutenção, ao mesmo tempo em que diminui o tempo de inatividade das turbinas eólicas. Este trabalho propõe uma estratégia para detectar falhas no estator em seu estágio inicial de forma não invasiva por meio de um módulo classificador que analisa os padrões ...