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ELECTRIC POWER ENGINEERING
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INTEGRAL MEASURE OF EVALUATION OF THE STATUS OF ENERGY SECURITY
Authors: Fedorchenko S.G., Fedorchenko G.S. State University of Transnistria, Tiraspol
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Abstract: We present a new approach of creation of the integral measure of estimation of energy security using a generalized Harrington-Menchers’s function. It is prezented an example of the construction of such a measure using real data. A detailed description of the Harrington-Menchers’s function is presented. In carrying out this work the analysis of the indicators recommended in the literature as components of energy security is made. It is shown that a significant part of these indicators is closely linked with each other. |
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Keywords: Generalized utility function, galaxy correlation, a display method, energy security.
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ANALYSIS OF ENERGETIC INDICES OF TRADITIONAL GEARED ELEVATING MECHANISM WITH TWO-SPEED ASYNCHRONOUS MOTOR FOR PASSENGER LIFTS
Authors: Boyko A. Odessa National Polytechnic University
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Abstract: In the article the technique of the mathematical description and researches of the two- speed asynchronous electric drive for the passenger lift of a traditional design is offered. The mathematical model is presented and its elements are described. The attention is paid to nonlinearities of the two-speed asynchronous electric drive and to detailed analysis of its energetic indices. The results of research of electromechanical transformation in the mechanism of the passenger lift with the two - speed asynchronous motor by a method of mathematical modeling are submitted. At researches are taken into account: variable parameters of an equivalent circuit of the asynchronous motor at work on high and low speeds, variable value of а worm gear reducer efficiency, load of a cabin, direction and real structure of a motion cycle of the lift, which moved under the optimum diagram. The results of modeling are checked up and are confirmed experimentally on the working passenger lift. |
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Keywords: Passenger lift, reducer, two-speed asynchronous electric drive, efficiency, modeling, energetic parameters.
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POWER ELECTRONIC SYSTEM FOR POWER ELECTRIC VEHICLES WITH ALGORITHMS OF SYNCHRONOUS MODULATION
Authors: Oleschuk V., Ermuratskii V. Institute of Power Engineering of the Academy of Sciences of Moldova
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Abstract: Schemes of synchronous space-vector modulation have been adapted for control of split-phase drive for electric vehicle with open-end windings of induction motor, supplied by several voltage source inverters. MATLAB-based simulation of processes in this system has been executed. It has been shown, that the use of algorithms of synchronous modulation provides symmetry of phase voltage waveforms for any ratio between the switching frequency and fundamental frequency, and for any voltage magnitudes of dc-sources. Spectra of the phase voltage of system do not contain even harmonics and subharmonics (of the fundamental frequency), which is especially important for drives for the medium-power and high-power electric vehicles. |
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Keywords: Adjustable speed AC drive for electric transport, voltage source inverters, space-vector pulsewidth modulation.
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INVESTIGATION OF SPECIAL ASYMMETRICAL MODES OF THREE-PHASE THREE-LEG AUTOTRANSFORMERS
Authors: Bosneaga V.A., Suslov V.M. Power Engineering Institute of Academy of Sciences of Moldova
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Abstract: On the base of earlier proposed model calculations were made and were investigated peculiarities of special asymmetric modes of three-phase three legs autotransformer (AT) with tertiary winding, connected in triangle. Calculations were carried out taking into account the electromagnetic coupling of coils, located on different legs. Modules and angles of currents and voltages vectors in autotransformer windings were calculated at breakage of one of the phases of the supply voltage and its simultaneous fault to ground at the side of AT. Based on these data vector diagrams were constructed, which give a visual representation of specific features of such regimes. Considered mode at grounded neutral is characterized by the occurrence of significant currents of the same value in all windings, app. equal to nominal current. Voltage of the windings varies slightly from the nominal values, except for the short-circuited phase. Furthermore, there is a considerable flow of the zero sequence flux, which may lead to additional heating of AT. At ungrounded neutral in this particular mode and absence of load on the secondary AT side, only a small magnetizing currents flows and neutral is significantly displaced. If the load is present, despite of the absence of the current in the neutral, currents in the windings, comparable with the nominal one appeared, also zero sequence flux appeared. In the general case, the currents of this failure (as in the previous case) are much smaller, than the usual short-circuit currents, so are insufficient to trigger the relay protection, this may require additional measures to protect AT against such damage. |
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Keywords: Transformer model, special asymmetric modes, autotransformer, three legs core, zero sequence magnetic flux.
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SIMULATION OF CHARACTERISTICS OF DUAL-CORE PHASE SHIFTING TRANSFORMER
Authors: Kalinin L., Golub I., Zaitsev D., Tirsu M., Institute of Power Engineering of Academy of Sciences of Moldova
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Abstract: The role and importance of phase shifting transformers are increased as a result of the further development of integrated power systems. This gives the rise to new technical solutions which entails the necessity of comparison of new developments with existing. The article consider the technical characteristics of dual-core phase shifting transformer which later will be used as a basis for comparison with other competing options and assess of their technical efficiency. |
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Keywords: Phase shifting transformer, phase shift angle, transformation ratio, comprehensive conversion factor.
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INFORATION SYSTEMS AND ROBOTICS
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SPECIAL ROBOTS FOR ENERGETICS
Authors: Sit M.L., (Institute of Power Engineering of the ASM), Shkolnik Sofia, Andreev E., Karpov E., Chisteakov М. (Lyceum ”Rambam”, Chisinau)
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Abstract: An overview of robots used in the power industry for diagnostics of power lines, cable lines, for the control, monitoring and maintenance of wind turbines, in nuclear energy, for optimum orientation of solar photovoltaic plants and solar panels for cleaning. Equations of statics and dynamics of robotic car which lifts along the vertical flexible rope are considered. It is presented the design which is made on the basis of "Lego Mindstorms" to solve the problem. |
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Keywords: Autonomous mobile robot, energetics, vertical rope climbing.
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STEGO TRANSFORMATION OF SPATIAL DOMAIN OF COVER IMAGE ROBUST AGAINST ATTACKS ON EMBEDDED MESSAGE
Authors: 1 A. Kobozeva, 1E. Lebedeva, 2O. Kostyrka 1Odessa National Polytechnik University, Ukraine 2Academy of Fire Safety named after Chernobyl Heroes, Ukraine
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Abstract: One of the main requirements to steganografic algorithm to be developed is robustness against disturbing influences, that is, to attacks against the embedded message. It was shown that guaranteeing the stego algorithm robustness does not depend on whether the additional information is embedded into the spatial or transformation domain of the cover image. Given the existing advantages of the spatial domain of the cover image in organization of embedding and extracting processes, a sufficient condition for ensuring robustness of such stego transformation was obtained in this work. It was shown that the amount of brightness correction related to the pixels of the cover image block is similar to the amount of correction related to the maximum singular value of the corresponding matrix of the block in case of embedding additional data that ensures robustness against attacks on the embedded message. Recommendations were obtained for selecting the size of the cover image block used in stego transformation as one of the parameters determining the calculation error of stego message. Given the inversely correspondence between the stego capacity of the stego channel being organized and the size of the cover image block, l=8 value was recommended. |
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Keywords: stego algorithm, robustness, attack against the embedded message, spatial domain, digital image.
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INDUSTRIAL ENGINEERING
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EXPERIMENTAL RESEARCH OF THE INFLUENCE OF VARIOUS TYPES OF SOLAR COLLECTORS FOR PERFORMANCE SOLAR DESALINATION PLANT
Authors: Rakhmatulin I.R. South Ural State University, Chelyabinsk, Russian Federation
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Abstract: The article discusses the possibility of using renewable energy for water purification. Results of analysis of a preferred energy source for a water purification using installed in places where fresh water shortages and a lack of electrical energy. The possibility of desalination of salt water using solar energy for regions with temperate climate. Presented desalination plant working on energy vacuum solar collectors, principles of action developed by the desalination plant. The experimental results of a constructed distiller when working with vacuum glass tubes and vacuum tubes with copper core inside. Conclusions about the possibility of using solar collectors for water desalination, are tips and tricks to improve the performance of solar desalination plant. |
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Keywords: Solar collector, a desalination plant, shortage of fresh water.
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MONITORING OF DISTRICT HEATING SYSTEM OF KISHINAU
Authors: Chernei M., Leu V. Joint Stock Company „Termocom”, Kishinau
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Abstract: The article describes basic modules of SCADA in district heating system of mun. Kishinau and some main components of it. |
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Keywords: District heating system, automated monitoring, telemetry systems.
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DETERMINATION OF THE INFLUENCE OF RANDOM FACTORS ON THE QUALITY AND RELIABILITY OF POWER SUPPLY
Authors: V.S. POPESCU Agrarian University of Moldova
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Abstract: The operation of power networks is accompanied by a number of issues including the key issue is the reliability of these networks. At the present stage in the transmission and distribution of electricity held a significant number of disconnections, subject to various random factors of influence. The problem of ensuring continuity and quality of electricity supply to consumers is a fairly current Republican power generation and its solution is imperative to know the influence factors and their impact on the reliability of the equipment installed in the electrical network. This paper is dedicated to the criteria for assessing the impact of influence factors on the reliability of electrical networks and forecasting mechanism and continuity of power supply to consumers. |
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Keywords: Quality of operation, electrical networks, indicators of reliability, random factors, characteristics of faults in electric networks.
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METHOD OF CALCULATION OF THE NON-STATIONARY TEMPERATURE FIELD INSIDE OF THERMAL PACKED BED ENERGY STORAGE
Authors: Ermuratschii V.V., Gritsay M.A. Institute of Power Engineering of the Academy of Sciences of Moldova
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Abstract: The paper presents a method of the approximate calculation of the non-stationary temperature field inside of thermal packed bed energy storages with feasible and latent heat. Applying thermoelectric models and computational methods in electrical engineering, the task of computing non-stationary heat transfer is resolved with respect to third type boundary conditions without applying differential equations of the heat transfer. For sub-volumes of the energy storage the method is executed iteratively in spatiotemporal domain. Single-body heating is modeled for each sub-volume, and modeling conditions are assumed to be identical for remained bod-ies, located in the same sub-volume. For each iteration step the boundary conditions will be represented by re-sults at the previous step. The fulfillment of the first law of thermodynamics for system “energy storage - body” is obtained by the iterative search of the mean temperature of the energy storage. Under variable boundary con-ditions the proposed method maybe applied to calculating temperature field inside of energy storages with packed beds consisted of solid material, liquid and phase-change material. The method may also be employed to compute transient, power and performance characteristics of packed bed energy storages. |
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Keywords: Sensible and latent heat storages, fixed packed bed, equivalent thermal network, thermal resistances, a phase change materials.
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