2011
Authors
Baptista, J; Moura, AM;
Publication
Proceeding of the International Conference on Electrical Power Quality and Utilisation, EPQU
Abstract
Power-Quality (PQ) is a crucial competitive and developing factor to all economic areas. The economic impact resulting from a bad PQ will be drastic to all consumers. Computers, uninterruptible power supplies (UPS), commuted power sources and fluorescent lamps/tubes are examples of nonlinear loads that have for main drawback the consumption of non-sinusoidal current. This paper presents a useful computer tool that can simulate and predict the behavior of non-linear loads and LV power systems with main focus on residential electrical grids. The paper also reviews some of the basic concepts and techniques related with power quality parameters and how they can be computed and presented in the simulation tool. The tool has an easy-to-use, friendly interface, and can be used as a tool to teach design techniques or as a laboratory to study the applicability of methods to real situations. The students can do simulations with their own data on Microsoft™ Windows® based platforms. © 2011 IEEE.
2011
Authors
Morais, R; Silva, NM; Santos, PM; Frias, CM; Ferreira, JAF; Ramos, AM; Simoes, JAO; Baptista, JMR; Reis, MC;
Publication
SENSORS AND ACTUATORS A-PHYSICAL
Abstract
Ever since the first studies about biomedical implantable devices, the problem of how to energize them has stood out as both important and notoriously difficult to solve. In order to extend the lifetime of implants, it is imperative to develop power generators that are autonomous, safe and maintenance-free. Energy harvesting is a natural way of meeting these requirements. First, the energy source is theoretically everlasting, a fact that helps to guarantee the autonomy. Second, the energy is obtained from the environment of the application itself, contributing to its safety. Finally, a properly designed energy harvesting system is very unlikely to ever require maintenance. This paper follows this line and describes an electromagnetic power transducer that harvests electrical energy from the human gait and stores it. An efficient power management module uses the stored energy to energize the telemetric system of a smart hip prosthesis implant, enabling the early detection of loosening, the target application of this work. The system is able to extract a total 1912.5 mu J of usable energy under normal walking conditions.
2010
Authors
Morais, R; Silva, N; Santos, P; Frias, C; Ferreira, J; Ramos, A; Simoes, J; Baptista, J; Reis, M;
Publication
EUROSENSORS XXIV CONFERENCE
Abstract
This paper describes an improved micro-power electric generator where energy harvested from human movements is used as an everlasting mechanical energy source to suffice smart hip implant electronics power needs. Its architecture is designed so that the mechanical energy promotes the movement of a combination of magnets and a spring embedded inside a Teflon tube, used to reduce friction. The changing magnetic field induces current in two coils so that the output of the generator is the sum of their signals. The end result is like a double generator in one casing. Produced electrical energy is stored in an energy reservoir handed over to a power management module. Experimental results shows that energy harvested from human walking can be used as an effective power source for hip prosthesis implants. (C) 2010 Published by Elsevier Ltd.
2010
Authors
Valente, A; Soares, S; Morais, R; Baptista, JM; Cabral, M;
Publication
Proceedings - 1st International Conference on Sensor Device Technologies and Applications, SENSORDEVICES 2010
Abstract
Recent developed button heat pulse probes (BHPP) demonstrated a great potential for soil water content measurements. This new probe compared to conventional heat pulse probes (HPP), does not use needles, and measurement accuracy is significantly improved. This new design, with the possibility to assembly the probe and electronics in the same package, with low-cost, and with less power consumption compared to conventional HPP, make it suitable to be connected to wireless data acquisition systems in precision agriculture. The probe was tested in agar to demonstrate the potential advantages of the button heat pulse sensor for soil water content measurements. It was possible to have an 0.5 °C temperature rise with only 156mW of power consumption, a ten times power reduction in heat-pulse soil water content measurements. These tests showed the potential use of the button heat pulse sensor for the determination of soil water content. © 2010 IEEE.
2010
Authors
Baptista, J; Morais, R; Valente, A; Soares, S; Bulas Cruz, J; Reis, MJCS;
Publication
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS
Abstract
In this paper we present a software tool to be used in residential/household generic power circuitry analysis and simulation, under non-linear loads. This tool can both be used by electrical engineers and by students of electrical engineering. It has an easy-to-use, friendly interface, and can be used to teach design techniques or as a laboratory tool to study the applicability of known methods to real world practical situations. Also, the users may supply their own data. The simulated results are very close to the measured ones.
2010
Authors
Baptista, J; Gonçalves, J; Soares, SFSP; Valente, A; Morais Dos Santos, R; Bulas Cruz, JAM; Reis, MJCS;
Publication
19th International Conference on Electrical Machines, ICEM 2010
Abstract
The main aim of this paper is to analyze the behavior of the three-phase squirrel cage induction motor under different voltage fluctuation levels. To achieve this goal several simulations were performed using the EMTP/ATP tool. Here we present how mechanical torque, speed and efficiency parameters varied with different levels of voltage fluctuation and modeling frequencies. As it was expected, the induction motor is sensitive to voltage fluctuations within certain amplitude levels and frequencies. Also, the speed is more affected by low frequencies and high amplitudes of voltage fluctuations, while the torque and efficiency are more affected by middle and high frequencies and amplitudes. ©2010 IEEE.
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