Browsing by Author "Savvin, Oleksandr V."

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    Calculation of the Probability of Test Object Compliance with the Specified Requirements and Non-Binary Decision-Making Rules
    (MM Publishing s.r.o., Praha, Czechia, 2024) Rimar, Miroslav; Fedak, Marcel; Kulikov, Andrii; Bilonozhko, M. V.; Rudko, K. V.; Martynova, V. V.; Yeromin, Oleksandr O.; Savvin, Oleksandr V.; Sukha, Iryna V.; Krenicky, Tibor
    ENG: The probability of test object compliance with the specified requirements and non-binary decision is a measure of how likely the test object is to meet the criteria for acceptance or rejection based on multiple factors. It is necessary to calculate by using a valid mathematical model that takes into account the test object's characteristics, the test conditions, the test criteria, and the uncertainty of the measurements. The significance of the probability of test object compliance with the specified requirements and non-binary decision can help to evaluate the quality, reliability, and performance of the test object, as well as to support decision making in complex situations.
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    Identification of the Thermal Process in an Induction Motor
    (Dnipro University of Technology, Dnipro, Ukraine, 2022) Kuznetsov, Vitalii V.; Tryputen, M.; Nikolenko, Anatolii V.; Tsyplenkov, Dmytro; Kuvaiev, Victor; Savvin, Oleksandr V.
    ENG: Purpose: synthesis of a mathematical model of an asynchronous motor, taking into account the impact of changes in the quality of electricity on the processes of heating and heat exchange for an economically justified choice of means of protection. Methodology: Theoretical substantiation of the expediency of using a one-mass thermal model of an asynchronous motor, for the conditions of operation of the latter in conditions of low-quality electricity, in order to determine losses in it. Results: Experimental studies of the operation of an asynchronous motor at nominal load were carried out. The obtained results of the measurements made it possible to determine the parameters of the single-mass thermal model, the heat transfer coefficient of the engine, and the coefficient of its heat capacity. A single-mass thermal model of an induction motor is a mathematical model used to describe the thermal processes occurring in an induction motor. This model is based on the assumption that all motor elements can be combined into one mass that heats up during engine operation. The model assumes that the thermal capacity of the motor is a constant, and the heat flow that is released during the operation of the motor is proportional to the square of the current passing through the motor windings. In addition, the model assumes the presence of thermal conductivity between the mass of the motor and the external environment, which affects the rate of heat dissipation. Scientific novelty: A methodology for determining losses in an asynchronous motor using a synthesized mathematical model is proposed, taking into account the influence of changes in the quality of electricity on the processes of heating and heat exchange in it. Practical significance: The obtained results indicate the adequacy of the proposed thermal model of an asynchronous motor operating in a network with low-quality electricity. Taking into account the fact that for many types of engines in the reference literature, there are no necessary data on the coefficients of heat transfer and heat capacity, and only the thermal time constants for certain types of engines are given, the value of the specified parameters of the model can be obtained on the basis of the methodology presented in the work. A single-mass thermal model can be useful for analyzing the thermal processes occurring in an induction motor and for improving the efficiency of the motor. In particular, it can help determine the optimal operating temperature of the motor, as well as calculate the necessary cooling system to ensure stable operation of the motor under conditions of variable load and temperature conditions.
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    The Influence of Reactive Power Compensation Methods on the Burning Characteristics of Shunted Electric Arc in an Ore Reduction Furnace
    (Dnipro University of Technology, Dnipro, 2024) Nezhurin, Vadym I.; Nikolenko, Anatolii V.; Tsyplenkov, D.; Bobrov, O.; Fedorov, Serhii S.; Savvin, Oleksandr V.
    ENG: The purpose of the work was to study the effect of compensation on the stability of the combustion of an electric arc in the furnace bath. Methodology. The results of the research of operating furnaces by traditional methods, such as measurement and oscillography of the form of voltage and current on the electrodes during the smelting of ferroalloys, were used. Results. Schemes of transverse capacitive compensation on the high or medium voltage side and longitudinal capacitive compensation in the medium voltage circuit of the furnace transformer are used for Electric ore reduction furnaces. Electric ore reduction furnaces are large consumers of reactive power, and their power has already reached such an amount that the value of the inductive voltage drop becomes unacceptably large; and their natural power factor does not exceed the value of 0.6–0.7. Compensation of the reactive power of the longitudinal compensation devices is traditionally resolved by usage of capacitor banks. Determined that longitudinal compensation devices are based on the phenomenon of voltage resonance, then if there are active, inductive and capacitive resistances in the furnace circuit – the arc burns continuously, even in the case of partial compensation. This mode occurs at a power factor of about 0.85. In case of full compensation of the inductive component of resistance of the furnace circuit, the mode of arc burning changes and becomes intermittent. Scientific novelty. Determined that with a fixed value of the power factor and the value of conductivity bc, it is very difficult to achieve ideal current resonance, and when bc = −⌂bl+bl+⌂blс the burning mode of the electric arc will be continuous; however, if the capacitive conductivity becomes more inductive, overcompensation is possible. In the case of transverse compensation, the total power of the furnace unit should be approximately 10% higher. Practical significance. The results obtained can be used for a reasoned selection of reactive power compensation installations for existing ore reduction electric furnaces. With full compensation of the reactive power (transverse and longitudinal), the arc burning mode of the ore reduction furnace becomes intermittent.
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    Nonlinear Analysis of Bifurcatory Properties of Mathematical Model of Subpopulation Dynamics in the Case of a Single Niche for Subpopulation
    (IEEE, 2022) Kuzenkov, Olexandr; Busher, Victor; Chornyi, Oleksii; Nikolenko, Anatoliy V.; Kuznetsov, Vitaliy V.; Savvin, Oleksandr V.
    ENG: The article is devoted to the use of mathematical models of the dynamics of heterogeneous populations, and computer simulation based on the above models allows to identify general trends in subpopulations, predict the state of the system and obtain results on possible consequences of artificial intervention. Also, the use of mathematical models can predict the spread of genetic anomalies. The authors propose a model of subpopulation dynamics with a logistic function as a basic one. It is concluded that the system-wide dynamics of subpopulation processes depends not only on the reproductive potential of subpopulations, but also on the intrasystemic dynamics that objectively occur in such systems. The adequacy of the proposed mathematical model is proved. © 2022 IEEE.