Analysis and monitoring of electrical grounding grid encapsulated with concrete: case study using simulation in finite element method

This work study the influence of concrete, plaster, clay and others buried structures in grounding systems. Comparison of soil characteristics between dry and rainy seasons on different grounding systems. The study includes comparison of six different grounding system on dry season and wet season. Simulations in finite element method was performed for tree layer stratified soil and the electrostatic equipotential surfaces were mapped into the region of interest

Estimativa das Indutâncias de uma Máquina Síncrona a partir de Ensaio com Rotor Bloqueado

Este trabalho apresenta uma simulação computacional da máquina síncrona de pólos salientes (SPSM), utilizando as indutâncias obtidas experimentalmente dos enrolamentos do estator e do rotor. Para obter as indutâncias e suas derivadas utiliza-se o método Volt-Ampere implementado em um módulo de aquisição de dados. Uma rotina computacional é desenvolvida para realizar a simulação da máquina, que irá funcionar como gerador em sincronismo com a concessionária de energia elétrica. Para validar o método proposto, os resultados das medições de correntes obtidos nos terminais da máquina são comparados com os resultados obtidos na simulação em condições semelhantes de funcionamento

Reconditioning in synchronous operation with one parallel induction generator

The purpose of this paper is to compare mathematical modeling and practical bench in order to validate the electrical interactions between an induction generator and a synchronous generator. Two generators was connected to a common bus in steady state, subject to non-linear load. The results comparing modeling and bench tests show that the induction generator besides the active power increasing, has a better way for harmonic currents flowing in common bus. It was concluded that the induction generator repowering and attenuates current harmonic components present at the connection point, improving the network voltage profile

Does resistance training improve body image satisfaction among the elderly? A cross-sectional study

OBJECTIVE: This study aims to evaluate whether body image satisfaction improves with practice in resistance training in elderly women. METHODS: Forty women were selected and randomly divided into an untrained group (UN) group and a group trained in resistance exercises (RT). To evaluate body image satisfaction, the silhouette matching task was used. RESULTS: No differences were found between current (5.45±0.24) and ideal (4.7±0.12) silhouettes in the RT group. However, the UN group showed a significant difference (po0.01) between current (10.4±0.43) and ideal (5.6±0.26) silhouettes. The current silhouette was significantly different between the UN and RT groups (po0.002). However, the ideal silhouette value did not differ between them. Body satisfaction was present in 90% of the participants in the RT group, and the difference was 15% less than that in the UN group (x2 test, po0.001). CONCLUSION: Resistance training in elderly women can promote satisfaction with their body image

Geoelectric method applied in correlation between physical characteristics and electrical properties of the soil

This paper presents the study of the relationship between electrical properties and physical characteristics of the soil. Measures of apparent electrical resistivity of the soil were made for different types of soil, varying moisture content gradually while maintaining a constant compaction, and then varying the compaction and relating it to a constant humidity. Development of a correlation surface is proposed in order to identify granulometry of the soil from moisture and compaction measurements. For the study of spatial variability, two areas were chosen to allow the change of moisture content and compaction in order to verify the measurement capacity of apparent electrical resistivity of the soil as methodology to identify change in soil dynamics. Results obtained show correlations among apparent electrical resistivity of the soil, moisture, soil compaction and clay content

Uma modelagem da máquina síncrona considerando o efeito da curvatura da sapata polar

This work develops a new mathematical model to the salient pole synchronous machines (SPSM), based on the abc reference system. The model considers the distribution and coil pitch factors of windings and develops a new function for the variable air gap, generated by the curvature of the polar mass. As a result, the development of the modeling takes into account the spatial harmonic components of: magneto motive force MMF(θ)h, electromagnetic ux density B(θ)h and variation function of the air gap g(θ)h. It is also proposed a new and simplied methodology using the locked rotor tests, volt-ampere method, to obtain the constants of the synchronous machine design, which allow the calculation of the modeling parameters and the terminals magnitudes determination. It presents also contributions to traditional methods of obtaining experimental inductances, using the locked rotor test. Yet it develops procedures and makes the simulation of the main temporal magnitudes at the generator terminals connected to the utility grid, electrical torque, speed, voltage and current. The model is validated through the theoretical and experimental confrontation of inductances, and also of the voltages and currents at the generator terminals connected to the utility grid.Doutor em CiênciasEste trabalho desenvolve uma nova modelagem matemática para as máquinas síncronas de polos salientes (MSPS), baseada no sistema abc de referência. A modelagem considera os fatores de distribuição e de passo de bobina dos enrolamentos e desenvolve uma nova função para o entreferro variável, gerado pela curvatura da sapata polar. Como conseqüência o desenvolvimento da modelagem leva em consideração os componentes harmônicos espaciais de: força magneto motriz FMM(θ)h, densidade de uxo eletromagnético B(θ)h e da função de variação do entreferro g(θ)h. É também proposto uma nova e simplificada metodologia a partir dos testes de rotor bloqueado, método volt-ampere, para a obtenção das constantes de projeto da máquina síncrona que possibilitam os cálculos dos parâmetros da modelagem, bem como a determinação das grandezas terminais. Também apresenta contribuições aos métodos tradicionais de obtenção de indutâncias experimentais, a partir dos testes de rotor bloqueado. Ainda desenvolve os procedimentos e faz a simulação das principais grandezas temporais nos terminais do gerador conectado à rede da concessionária: torque elétrico, velocidade, corrente e tensão. A modelagem é convalidada através das confrontações teórico-experimental das indutâncias, e também dos resultados de correntes e tensões nos terminais do gerador conetado à rede da concessionária

Analysis and monitoring of electrical grounding grid encapsulated with concrete: case study using simulation in finite element method

This work study the influence of concrete, plaster, clay and others buried structures in grounding systems. Comparison of soil characteristics between dry and rainy seasons on different grounding systems. The study includes comparison of six different grounding system on dry season and wet season. Simulations in finite element method was performed for tree layer stratified soil and the electrostatic equipotential surfaces were mapped into the region of interest

Transferrin polymorphism in Amazon turtle (Podocnemis expansa) stocks

The transferrin gene locus (Tf) was investigated in five populations of the Amazon turtle (Podocnemis expansa) sampled from five geographical areas in the Amazon region. This locus was polymorphic, showing three genotypes (TfaTfa, TfaTfb and TfbTfb), presumably encoded by two co-dominant alleles, Tfa and Tfb. All populations showed good genetic balance according to Hardy-Weinberg expectations, and may sustain the hypothesis of a single stock in the area investigated. The data are consistent with free flow of genes among the population samples examined

Reconditioning in synchronous operation with one parallel induction generator

The purpose of this paper is to compare mathematical modeling and practical bench in order to validate the electrical interactions between an induction generator and a synchronous generator. Two generators was connected to a common bus in steady state, subject to non-linear load. The results comparing modeling and bench tests show that the induction generator besides the active power increasing, has a better way for harmonic currents flowing in common bus. It was concluded that the induction generator repowering and attenuates current harmonic components present at the connection point, improving the network voltage profile

Electromagnetic Problems Solving by Conformal Mapping: A Mathematical Operator for Optimization

Having the property to modify only the geometry of a polygonal structure, preserving its physical magnitudes, the Conformal Mapping is an exceptional tool to solve electromagnetism problems with known boundary conditions. This work aims to introduce a new developed mathematical operator, based on polynomial extrapolation. This operator has the capacity to accelerate an optimization method applied in conformal mappings, to determinate the equipotential lines, the field lines, the capacitance, and the permeance of some polygonal geometry electrical devices with an inner dielectric of permittivity ε. The results obtained in this work are compared with other simulations performed by the software of finite elements method, Flux 2D