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The aim of the work was to simulate the residual stresses and distortion of an electric arc welding with tungsten electrode and gas shielding of a hypoeutectoid steel, using the finite element method, the microstructural transformations and taking into account the effect of the filler material, an element little studied in the specialized literature that focuses more on autogenous welds. The modelling was divided into two stages: one thermal simulation and another structural simulation. The thermal-dependent properties of an ASTM A210 Gr. A1 steel and an ER - 70S6 wire were used. The spots were analyzed in the thickness of the plate and at different lengths of the weld center. The results obtained were similar to those reported in the literature. The maximum stresses were tensile. The most important values of total distortion were found at less than 20 mm from the weld center. Above this length, they are practically nil. A marked difference between longitudinal and transverse residual stresses was found in the molten zone. [ABSTRACT FROM AUTHOR]

This work shows a methodology known as the S Transform for time-frequency analysis of different distortions in electric power systems, which mostly are non-stationary and short-duration events, due to the contribution of network impedances and loads types connected by the users. The ability to identify all types of power quality distortions encrypted in the current and voltage signals is very important for failures and malfunctions analysis of monitoring equipment, protection, and control of electrical networks. An important feature of the S Transform is that it combines a frequency dependent resolution of time-frequency space, with information fully connected to the local phase. This allows defining the term of local phase spectrum. Additionally, it shows that amplitude response is invariant from frequency, in contrast to Wavelet and Short Time Fourier Transforms. The following study cases will be simulated by means of PSCAD software: motors starting up and shutting down, line-ground fault, zero-sequence harmonics in a balanced three-phase load, unbalanced three-phase load, a signal with high frequency components and notches presence. [ABSTRACT FROM AUTHOR]

This paper presents the design, simulation and implementation of a small scale battery charger with low harmonic distortion in current. It was proposed a design composed of two boost converters in cascade, the first operating as PFC and second as a regulator of the injected current to the batteries. Additionally, it was presented the procedure for the controllers design of each stage. In the first stage was used a control in average current mode and in the second stage were used two controls that enable you to employ the method of constant current - constant voltage in order to charge the batteries. In both stages were used the PI controllers and with the power electronic circuit were simulated in the PSIM® and MATLAB® software and validated experimentally In this tests, power factors close to 0.98 and harmonic distortion in current below 10% were obtained, complying with the requirements of the IEC 61000-3-2 standard. Finally, the conclusions are presented. [ABSTRACT FROM AUTHOR]

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The current paper addresses the design of an electronic system using XBee modules to transmit voice. These modules operate on the IEEE 802.15.4 wireless standard, which is not originally intended to transmit voice. A configurable model is presented as both, a master or a terminal device. The printed circuit board supporting this application and operation is discussed. A terminal equipment is programmed through the use of a protocol, this specifically designed for acquiring, digitizing, compressing and packing the voice signal using a microcontroller. Packages are delivered via serial communication to an XBee module that allows wireless communication with other XBee module located in the master device. The master device performs the function of managing receiver in order to reconstruct the voice signal. Moreover, the structure of the various commands is shown. This commands are used for implement the communication protocol and allow to monitor the terminal devices by the master device. Finally, the results are obtained using two complementary models and the distortion of the received signal is analyzed. [ABSTRACT FROM AUTHOR]

A study of Joule losses in electrical feeder lines carrying harmonic currents is presented. Different formulae proposed in the literature were used to estimate the neutral current and electrical losses. In the environment of the Alternative Transients Program, different levels of harmonic distortion were simulated, arriving at findings that show that losses may become considerably higher than in the condition in which active power without distortion is carried. A real case and the importance of reducing the harmonic content associated with losses are analyzed. [ABSTRACT FROM AUTHOR]

Introduction. This paper introduces a new method of islanding detection for distributed energy generation systems. Objective. To demonstrate that, with the method proposed, it is possible to achieve detection time measurements within the security margins defined by the regulations. Materials and methods. The method was implemented on a 230 W inverter. This method is based on the introduction of a disturbance at the inverter's output and the subsequent observation of the tension in the common coupling point (CCP), which depends on the impedance connected to the latter, in an islanding situation. The islanding detection is based on the Fourier's analysis. Results. Simulation and experimental results are provided, under several load and net conditions, achieving, in all cases, adequate detection times, not affecting the inverter's performance in terms of harmonic distortion or reactive power. Conclusions. The method proposed, if compared to others based on the injection of harmonics, can detect the islanding situation by the use of the Fourier's analysis applied to a unique harmonic, with no degradation of the power quality and within the time periods defined by the regulations. [ABSTRACT FROM AUTHOR]

Copyright of Tecnura is the property of Tecnura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper both a method and apparatus are applied to different configurations of thyristor-based ac/dc rectifiers to reduce the distortion of currents flowing from the ac supply. The load may be either inductive or capacitive. The technology involves an accurate shaping of the dc current by using two self-commutated switches. This dc-current shaping is reflected back into the shaping of the ac input currents, which become pure sine waves. The control circuit is simple, and also able to deal with both rapid load variations and failures in the self-commutated switches. Furthermore, the overlap conduction of bridge thyristors is eliminated completely. Experimental verification is provided from a 400-V 50-Hz 30-kVA laboratory prototype. [ABSTRACT FROM AUTHOR]

Using the SGFM (Surface Green's Function Matching) method and the tight-binding approximation we have studied the electronic states of(112) metallic surface of CuInSe2. In this work, we include tetragonal and anion distortions. Because the parameters of the bi-dimensional unitary cell and the distance between atomic planes change when we include these distortions, in consequence, the surface electronic states change too. We study the influence of the distortion on both the dispersion diagrams and Local Density of States (LDOS). Surface states were found in both cases and the effect of the distortions is strong. Such states are localized into the energy gap of the material. We have not considered reconstructions or relaxation of the surface. The inclusion of distortion in the study of the electronic states in the surface is made for the first time, as we know at present. [ABSTRACT FROM AUTHOR]