Proposta de uma metodologia de rebobinamento para converter motor de indução trifásico em monofásico

This paper proposes the conversion of a three-phase induction motor into single phase through rewinding its stator. It presents a methodology to calculate this rewinding process considering the constructive parameters of the, such as number of slots and number of poles, for instance. The operating principles of DC motors are highlighted to introduce the logic involved in the calculation of lap and wave windings. The construction of the stator three-phase induction motor generally uses the lap winding, which is also used in single phase to perform the conversion. The rewinding process is widely used for reconstruction of industrial and residential electric motors that have suffered damage or present flaws with use. Therefore, many three-phase electric motors that are discarded or disposed of could be recovered by the method described in this work for a purpose that contributes to energy efficiency or simply saving resources in single-phase uses

Chaveamento de cargas intermitentes usando sensor de corrente

Due to concerns about rational use of energy, several alternative technologies of power generation appeared, including the conversion of solar energy into electrical energy by photovoltaic panels. In low-income households, the refrigerator represents considerable impact on the electric bill, since it requires constant power given its use in food preservation. It is possible to reduce this share, with the use of an alternative energy source. This work presents a timed switching electronic system, which allows commercial equipment that is not affected by short interruptions in the power supply to use a photovoltaic panel as a source of alternative energy, which usually do not provide energy continuously. Switching is made automatically in case of low incidence of sunlight, and without any form of energy storage. Between each switching, there is a dead time without power supply, therefore preventing the use of synchronizers circuits between the photovoltaic panel and the public power grid. A circuit containing a 80C31 microcontroller is used to control the system’s switching. The photovoltaic panel’s voltage inverter is in H bridge configuration, and is also controlled by the microcontroller through Pulse Width Modulation, which makes use of preprogrammed tables to generate the control signals of the power transistors. Through the use of software simulations, the proposed system was tested, which is capable of supplying intermittent single-phase loads. The simulations indicates that the project developed in this paper can be assembled into a prototype and be tested under real operating conditions, as long as the scaling of components, the characteristics of the photovoltaic panel to be used, and the project involved load are taken into account

Structural and functional characterization of barium zirconium titanate/epoxy composites

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SnO2 dense ceramic microwave sintered with low resistivity

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Piezoresponse force microscopy behaviour of Bi4Ti3O12 ceramics with various excess bismuth

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dielectric response of tungsten modified Ba(Ti0.90Zr0.10)O3 ceramics obtained by mixed oxide method

The electrical response of Ba(Ti0.90Zr0.10)O3 (BZT) ceramics obtained by the mixed oxide method as a functionof tungsten content was investigated. According to X-ray diffraction analysis the single phase BZT1W (1wt.% W doped BZT) and BZT2W (2 wt.% W doped BZT) ceramics, crystallized in a perovskite structure, wereobtained. It is also shown that tungsten substituted ceramics can be sintered at a reduced temperature whencompared to the undoped BZT. Electron paramagnetic resonance (EPR) analyses reveals that substitution ofTi4+ by W6+ causes distortion in the crystal structure changing lattice parameter. Substitution of W6+ on B-siteof ABO3 perovskite BZT ceramics shifted the phase transition to lower temperatures up to a tungsten contentof 2 wt.% leading to a relaxor-like behaviour.Keywords: donor dopant; ceramics; dielectric response; mixed oxide method

Avaliação da deposição e da agitação de calda em reservatórios de pulverizadores agrícolas utilizando uma análise numérica (CFD) e experimental

Pós-graduação em Engenharia Mecânica - FEB

The role of oxygen vacancies and their location in the magnetic properties of Ce1-xCuxO2-delta nanorods

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Pigments based on Cr and Sb doped TiO2 prepared by microemulsion-mediated solvothermal synthesis for inkjet printing on ceramics

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Studies on structural, morphological and electrical properties of Ce1-xErxO2-delta (x=0.05-0.20) as solid electrolyte for IT - SOFC

A series of four different powders ceria doped Ce1-xErxO2-delta (0.05 <= x <= 0.20) were synthesized by applying self-propagating reaction at room temperature (SPRT method). SPRT procedure is based on the self-propagating room temperature reaction between metal nitrates and sodium hydroxide, wherein the reaction is spontaneous and terminates extremely fast. The method is known to assure very precise stoichiometry of the final product in comparison with a tailored composition. XRPD, Raman spectroscopy, TEM and BET measurements were used to characterize the nanopowders at room temperature. It was shown that all obtained powders were single phase solid solutions with a fluorite-type crystal structure and all powder particles have nanometric size (about 3-4 nm). Densification was performed at 1550 degrees C, in an air atmosphere for 2 h. XRPD, SEM and complex impedance method measurements were carried out on sintered samples. Single phase form was evidenced for each sintered materials. The best value of conductivity at 700 degrees C amounted to 1.10 x 10(-2) Omega(-1) cm(-1) for Ce0.85Er0.O-3(2-delta) sample. Corresponding activation energies of conductivity amounted to 0.28 eV in the temperature range 500-700 degrees C. (C) 2015 Elsevier B.V. All rights reserved.

Dielectric properties of Sr0.75Ba0.25Nb 2O6 thin films: Bias field, frequency and temperature dependence

Ferroelectric strontium barium niobate solid solutions had received great attention due to their excellent pyroelectric, electrooptic and photorefractive properties. Furthermore, they usually also present very interesting phase transition characteristics. In this work, polycrystalline single phase Sr 0.75 Ba 0.25 Nb 2 O 6 thin films were prepared by a hybrid chemical method and deposited on Pt/Ti/SiO 2 /Si substrates. The temperature dependence of dielectric constant was measured at different frequencies and bias field levels. The presence of two dielectric dispersion regions with relaxor characteristics was observed at distinct temperature ranges, corresponding to the ferro-paraelectric and to a structural phase transition at low temperatures, respectively. A specific dielectric dispersion region, associated with an incommensurate superstructure frequently observed in bulk samples, was not observed in this films probably due to their small grain sizes. © 2002 Taylor & Francis.

Representation of transmission lines: comparison of models and parameters distributed discrete parameters

A transmission line is characterized by the fact that its parameters are distributed along its length. This fact makes the voltages and currents along the line to behave like waves and these are described by differential equations. In general, the differential equations mentioned are difficult to solve in the time domain, due to the convolution integral, but in the frequency domain these equations become simpler and their solutions are known. The transmission line can be represented by a cascade of π circuits. This model has the advantage of being developed directly in the time domain, but there is a need to apply numerical integration methods. In this work a comparison of the model that considers the fact that the parameters are distributed (Universal Line Model) and the fact that the parameters considered concentrated along the line (π circuit model) using the trapezoidal integration method, and Simpson's rule Runge-Kutta in a single-phase transmission line length of 100 km subjected to an operation power. © 2003-2012 IEEE.

Retificador entrelaçado com elevado fator de potência para operação de um veículo trólebus alimentado por redes em CA Ou CC

This paper presents the development and the main results for an interleaved boost rectifier operating as a special input power stage for a trolleybus type vehicle, allowing its feeding by alternate current (AC) or direct current (DC) distribution power systems. When feeding with two wires (single phase) alternate current distribution system, the converter accomplish active power factor correction, providing a relatively sinusoidal current with low total harmonic distortion (THD) and fully complying with IEC 61000-3-4 standards. In addition, a management control system promotes the required automatic operation changes for the proposed rectifier when the vehicle is changing from the DC distribution power system to the AC distribution power system and vice-versa, keeping its original electrical DC system characteristics for the adjustable speed driver sub-system. The main experimental results for a prototype rated at 150kW are presented, considering its application for a trolleybus with DC adjustable speed driver, demonstrating the proposed converter benefits and the possibility of AC feeding system for trolleybus type vehicle.

Microinversor integrado ao módulo fotovoltaico para sistemas conectados à rede elétrica utilizando controlador ressonante

This paper shows the modeling and control of a single-phase full-bridge inverter with high-frequency transformer that may be used as part of a two-stage converter with transformerless DC-DC side or as a single-stage converter (simple DC-AC converter) for grid-connected PV applications. The inverter is modeled in order to obtain a small-signal transfer function used to design the P+Resonant current controller. A highfrequency step-up transformer results in reduced voltage switches and better efficiency compared with converters in which the transformer is used on the DC-DC side. Simulations and experimental results with a 200 W prototype are shown. 1

Synthesis, structure and magnetic properties of Y3Fe5-xAlxO12 garnets prepared by the soft chemical method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)