Daily Archives: 14 December 2016

Electromagnetic Shielding System for Information and Communication Equipments

Abstract

Today, most of the human activities are computer-controlled with respect to equipments and platforms functionality, quality of the process and people and goods safety. Unlike the specialized platforms, where this feature is already implemented and developed according to the system architecture, in many other applications this function can be achieved by including a simple desktop or laptop and the specific software application in the platform original configuration. These applications can be also very sensitive, in terms of safety, quality and costs, so the whole controlling process must be accurate, stable and robust. One of the main problems that can occur and affect these systems workability is represented by electromagnetic interference (EMI) presence and the complementary issues, especially when the scenario takes place in a hard electromagnetic environment (industrial, military, IT&COM high-density areas etc.). There are some technical approaches to solve this inconvenience, but most are focused to adapt the current equipment configuration, which was intended to work in a specific environment and to provide specific features, to the new place working requirements. Our solution is to develop a self-independent EMI protection system that can be easily adapted to a large range of the IT&COM equipments in order to minimize costs, product performances distortion and overall time implementation. images

Technical Aspects Regarding Electromagnetic Compatibility Compliance of the Electric and Electronic Integrated Systems

Abstract

The modern world’s needs of electric and electronic devices and systems lead to a continuously electromagnetic interferences growing in ways that were hard to predict few decades ago, a serious reason to consider the electromagnetic compatibility (EMC) regulations a top priority for the developers and the end-users as well. An important segment of these products is represented by integrated systems, and not only the large scale ones, as a natural consequence of the increased equipments interoperability and versatility. The integrated systems developers are facing many issues regarding EMC products compliance, although the individual components of their systems are fully or partially compliant with the EMC standards and regulations. Practical solution to identify and solve these problems consists in preliminary precompliance tests deployed in specialized EMC laboratories. Unlike the classic EMC tests, the specialized pre-compliance probes enable the developers to improve their products, according to the provided feedback, and to minimize their efforts to reach that goal. Our specialized EMC laboratory has been involved in many testing and evaluation projects for different types of electric and electronic systems compliance characterization. The authors participated in experimentation activities as well as software simulation sfor EMI protection solutions design and realization. The accumlated experience allow us to investigate the associated phenomena related to EMC problems and to find solutions for these inconveniences images

Load Flow Analysis of Unbalanced Distribution Networks using Symmetrical Components Based Software

Abstract

This paper presents the algorithm and the main features of a Matlab (R2014a)-based software conceived by the authors for analysis of the asymmetrical operation of the three-phase distribution networks. The software’s algorithm is based on an iterative procedure of Newton-Raphson type. This algorithm is independently applied on three equivalent sequence networks and includes an equivalent model for the unbalanced loads supplied from the analysed distribution grid. In order to outline the capabilities of this software tool named PFASYM and illustrate the key concepts a comprehensive case study was considered. This one summarizes the results of a three-phase load flow analysis performed for a real representative 110/20 kV distribution network supplying industrial unbalanced loads. The PFASYM’s results are validated by comparison with those generated by a proprietary software package. The analysis methodology used in this illustrative case study and the results generated for different grid configurations could assist the grid operator in conducting the power flow studies of operational areas of interest. This work is part of an overall energy systems modelling and analysis project developed by the authors, in collaboration with the local power distribution operator. This one has as objective to facilitate the understanding of the power flow concepts for the present distribution networks operating in asymmetry conditions and to assist the grid operator in applying optimal mitigation measures. images

Aspects of Behavior Regarding Certain Electronic Equipment Subject to Electrostatic Discharge

Abstract

Electrical discharge due to human operators may cause disturbances with very fast variation reaching the sensitive equipment by conduction and radiation and can affect and even destroy them. Therefore, between a human, possible to load electrostatic voltages of 10-15kV ordinal, and an electronic device (computer, laptop, memory stick, etc.), system connected to the grounding, an electrostatic discharge can occur as a result of electric charging (electrification) the person wearing clothes made of synthetic fibers, due to friction with the air. This paper proposes a study of the transient arrangement produced by human electrostatic discharge and the disruptive or destructive effects that may occur. Experimental tests have been performed to determine the degree of immunity to electrostatic discharge (ESD) into the air and through direct contact, in accordance with the regulations in force, in the specialized laboratory of ICMET Craiova, subjecting a memory stick and a wireless Internet connection stick to electrostatic discharge. The results obtained revealed the individualized behavior for each device tested. images

On the Immunity of Data Acquisition Systems Used in Power Systems

Abstract

The paper deals with some tests regarding the immunity for radiated emissions and compliance with international standards for electromagnetic compatibility (EMC) measurements for an industrial data acquisition system (DAS) used in power systems. The behavior of the DAS, when functioning near electromagnetic disturbance sources, is studied. The goal is to test its robustness in similar conditions as those encountered in its normal environment. It is known that multiple factors may affect the accuracy of data acquired by DAS. The Equipment Under Test (EUT), witch in this case is represented by DAS is tested for immunity in a specialized enclosure (GTEM Cell). The immunity based on the analysis of the influences of an electric field with constant magnitude and variable frequency in the range of 80 MHz…1 GHz is studied. After analyzing the initial tests results, partial and, afterwards, full shielding of the EUT’s case is performed in order to remove the EM influence. The tests’ results drive to the conclusion that it is necessary to design and build an enclosure from conductive material for the DAS. After the implementation of the measures, the EUT passed the tests concerning the immunity. The GTEM Cell construction, GTEM model, generation and distribution of electric and magnetic field inside the GTEM Cell, equipment under test (EUT), radiated emission measurement scheme, EMC standards for GTEM Cell, are exposed. images

Comparisons Among p – Channel, n-Channel and Mixed n/p Channel OTFTs

Abstract

Some theoretical approaches of an alternative organic semiconductor device are presented in this work. The Organic transistors are based either on n-type or p-type or mixed p/n overlapped layers. The carrier modulation insides different films is carried out by two gates electrodes, as is usual in the thin film transistor field. This paper introduces some novel aspects for these kinds of organic transistors, selecting a suitable biasing regime. The simulations emphasize a stronger influence on the static characteristics when the superior gate is acted. One of the novelties of this paper concerns the electrical conduction occurrence by two simultaneous channels, in comparison with one volume channel conduction, for different gate voltage regimes. A similar work regime is also encountered in the SOI devices with ultra-thin films that develop a volume channel. The volume channel regime is advantageously when the technology of fabrication of the organic semiconductors on different insulators provides an extremely charged interface, which can degrade the surface currents. Comparisons and applications for both situations – with one volume channel or two accumulation channels – are finally discussed. The vertical n/p junction arose between the upper n-channel and the bottom p-channel, offers novel physical properties and prevented any interaction among channels. The device simulations revealed multiple behaviors, depending on the Top and Bottom Gate voltages, if a positive drain-source voltage is applied. images

The Analysis of Magnetic Field Measurements in a Public Access Area

Abstract

 This paper describes a case study referring to the magnetic field measurements performed in a public access area. Compared to the standard limits regarding the human exposure to electromagnetic fields, the measurement results were significantly higher. Based on these results and the scarce data regarding the magnetic field sources in the area, there are discussed several cases of power lines configurations and their corresponding magnetic field levels. images

Enhancing the dynamic frequency of microgrids by means of PV power plants with integrated energy storage

Abstract

Achieving a high-level of stability represents one major concern in autonomous microgrids (MGs) with high penetration levels of renewable energy sources. The aim of this paper is to study how photovoltaic (PV) power plants can provide dynamic frequency support in MGs, in order to obtain an improved stability for the entire power system. On the PV side an energy storage subsystem is added, with the main purpose of better control and higher power reserve of the PV power plant. By this way the necessary input power is provided by the PV system along with the battery block. The required output power is supplied by a three-phase voltage source converter (VSC). The VSC control is implemented in a rotating dq reference frame, including a harmonic compensation loop for the output current. To improve the dynamic frequency stability of the MG, specific functions are implemented within the PV inverter control. To highlight the performance of the proposed system, a comparative analysis is provided, which cover four cases of interest depending on the status of the storage system and dynamic support (i.e. with/without storage and with/without dynamic support). Simulation results are included to validate the power control system, showing that the dynamic frequency control can be improved by the proposed solution. images

Dynamic Regime Electromagnetic Torque in Brushless Direct Current Motors

Abstract

This study aimed at establishing the mathematical model for determining the dynamic regime torque and at emphasizing constructive aspects which influence its magnitude and variation. Brushless direct current motors are very present and there have been carried out researches regarding their design and optimum construction. The technology evolution in several areas has caused an increase in production of permanent-magnet BLDC motors, which has good technical-economic performances for a large range of controlled-speed applications. The study carried out, by the simulations we presented, shows that these motors have high torque oscillations in a complete rotation. There are identified the slots which create high torques, respectively low torques, in a complete rotation, thus justifying the oscillations. In this paper there is emphasized that the optimum variant of maximum torque involves a supply by six pulses per period in direct direction, also indicating the value of the control angle. The most unfavourable variant occurs at brushless direct current motor supplied by three pulses per period and reverse succession of phases, where the average value of the torque decreases by 56.7% over the optimum machine. A complete elimination of oscillations in this type of motor is not possible, but an optimal design can reduce them considerably images

Small Scale Model of Automatic Barrier Powered by Photovoltaic Panel

Abstract

Access control systems offer numerous benefits and are able to constitute extremely good solutions for securing an area of high or very high importance. An access control system allows restriction, monitoring and directing human trafficking as cars to a location or from a location. In generally at access control systems call the managers of circulated spaces or areas where must enter only authorized persons. To access the vehicles in different areas are frequently used automatic barriers. This paper presents such an access system, achieved a small scale named ˝automatic barrier model˝, that uses photovoltaic panels (PV) as main energy source. Automatic operation of barrier is provided by a development system achieved around a microcontroller. In the first part of paper is presents the structure and minimum requirements of development system. Also are highlighted aspects of dimensioning and design for both parts hardware and software respectively. To achieve electrical diagrams and PCBs was used a dedicated software. Finally was tested the achieved automatic barrier model. The tests consist of verifying the correct operation of the automated system. Were made test regarding to automation and to power supply from PV panel. Experimental results show a smooth functioning of experimental automatic barrier powered by PV panel and can be successfully expanded at real scale. images