Electrical Engineering and Power Engineering http://ee.zntu.edu.ua/ ISSN 1607-6761 (Print). ISSN 2521-6244 (Online)<o:p></o:p></span></b></p> <p class="MsoNormal" style="margin-top:6.0pt;margin-right:0cm;margin-bottom:0cm; margin-left:0cm;margin-bottom:.0001pt;line-height:normal"><span style="mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin">The scientific journal " <b style="mso-bidi-font-weight:normal">Electrical engineering and power engineering</b> " is a peer-reviewed open access scientific journal, that publishes work on new developments in the field of electrical engineering, electrical engineering, electric power engineering, as well as automation of computer-integrated technologies in the development and improvement of electrical machines and apparatus, power electronics, and issues of theoretical electrical engineering and electro physics, technology of strong electric and magnetic fields, cable technology, electric transport, power plants, networks and systems, their safety, as well as alternative energy sources.<o:p></o:p></span></p> <p class="MsoNormal" style="margin-top:6.0pt;margin-right:0cm;margin-bottom:0cm; margin-left:0cm;margin-bottom:.0001pt;text-align:justify;line-height:normal"><span style="mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin">Abbreviated key-title "<span class="SpellE"><b style="mso-bidi-font-weight:normal"><a href="https://portal.issn.org/resource/ISSN/2521-6244">Elektroteh. Elektroenerg</a></b></span><b style="mso-bidi-font-weight:normal">"</b><strong><span style="font-family: &quot;Calibri&quot;,sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font: minor-latin;mso-bidi-theme-font:minor-latin;font-weight:normal;mso-bidi-font-weight: bold">, </span></strong></span><span class="tlid-translation"><span style="mso-ansi-language:EN" lang="EN">transliteration of the title of the journal</span></span><span style="mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin" lang="EN"> </span><span style="mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin">"<span class="SpellE"><b style="mso-bidi-font-weight:normal"><a href="https://portal.issn.org/resource/ISSN/2521-6244">Elektrotehnìka ta elektroenergetika</a></b></span><b style="mso-bidi-font-weight:normal">"</b>, parallel title<span class="tlid-translation"> "</span><b style="mso-bidi-font-weight: normal"><a href="https://portal.issn.org/resource/ISSN/2521-6244">Electrical engineering and power engineering</a>"</b>,</span><span class="tlid-translation"><span style="mso-bidi-font-family:Calibri;mso-bidi-theme-font:minor-latin;mso-ansi-language: UK"> </span></span><span style="mso-bidi-font-family:Calibri;mso-bidi-theme-font: minor-latin">parallel title<span class="tlid-translation"> "</span></span><b style="mso-bidi-font-weight:normal"><span style="mso-bidi-font-family: Calibri;mso-bidi-theme-font:minor-latin;mso-ansi-language:RU" lang="RU"><a href="https://portal.issn.org/resource/ISSN/2521-6244">Электротехника<span style="mso-ansi-language:EN-US"> </span>и<span style="mso-ansi-language:EN-US"> </span>электроэнергетика</a></span></b><span style="mso-bidi-font-family:Calibri; mso-bidi-theme-font:minor-latin">"<o:p></o:p></span> Zaporizhzhia Polytechnic National University en-US Electrical Engineering and Power Engineering 1607-6761 <h3 align="justify"><span style="font-size: small;">Creative Commons Licensing Notifications in the Copyright Notices</span></h3><p align="justify"><span style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: small;">Authors who publish with this journal agree to the following terms:</span></p><ul><li><p align="justify"><span style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: small;">Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a<a href="http://creativecommons.org/licenses/by/3.0/" target="_new">Creative Commons Attribution License</a> that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.</span></p></li><li><p align="justify"><span style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: small;">Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.</span></p></li><li><p align="justify"><span style="font-family: Verdana, Arial, Helvetica, sans-serif; font-size: small;">Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work.</span></p></li></ul> The influence of nonlinear load on the autonomous electrical network at parallel work of the active power filter http://ee.zntu.edu.ua/article/view/220864 <p class="a"><strong>Purpose.</strong> The purpose of the article is to investigate the modes of operation of a three-phase active power filter in the composition of an autonomous electrical network when connected to a network of three-phase nonlinear load of different spectral character.</p><p class="a"><strong>Methodology.</strong> For the research, the provisions of the pq-theory of power, the theory of electrical circuits, the theory of automatic control, mathematical modeling in the Matlab package were used.</p><p class="a"><strong>Findings. </strong>The graphs and spectral composition of the mains voltage and load current have been obtained, which makes it possible to evaluate the effectiveness of using a power active filter in the filtration mode as part of an autonomous electrical network, which is a synchronous generator.<strong> </strong></p><p class="a"><strong>Originality.</strong> The efficiency of the parallel operation of a power active filter in the filtration mode with a synchronous generator at an abruptly variable nonlinear load is proved.</p><p class="a"><strong>Practical value.</strong> The use of the proposed technique will make it possible to create a three-phase power active filter for its use in autonomous electrical networks, represented by a synchronous generator with automatic regulation of the excitation voltage. </p> R.V. Vlasenko O.V. Bialobrzheskyi Copyright (c) 2020 R.V. Vlasenko, O.V. Bialobrzheskyi https://creativecommons.org/licenses/by/4.0 2020-12-24 2020-12-24 2 40 50 10.15588/1607-6761-2020-2-5 Parametric control of efficiency of asynchronous drive by means of converter with the increased power factor http://ee.zntu.edu.ua/article/view/220821 <pre><strong><em>Purpose.</em></strong> <em>Development of circuit solution and substantiation of parameters of control system and power part of power supply converter, provided its operation with high power factor and smooth or stepwise methods of energy efficiency control of asynchronous drive.</em></pre><pre><strong><em>Methodology</em></strong><strong>.</strong> <em>The provisions of the theory of electric machines, methods of circuit design of automatic systems in the Multisim component of the National Instruments electronic laboratory, mathematical modeling in the Matlab package were used for research</em><em>.</em><em> </em></pre><pre><strong><em>Findings.</em></strong><strong> </strong><em>Digital models of pulse-phase control systems for stepwise and smooth regulation of the supply voltage of motors using the method of pulse-width modulation of the mains voltage have been developed and built, recommendations are given for the level of load sagging, at which it is necessary to reduce the supply voltage and its magnitude with relay control, and also tested a smooth control system with coordinate-phase duty cycle control to achieve rational energy efficiency of the drive. </em></pre><pre><strong><em>Originality. </em></strong><em>The choice of the switching limit of the relay regulator and the level of rational value of the converter</em><strong> </strong><em>output voltage </em><em>is substantiated</em><em>, at which rational and energy-efficient control of the drive is achieved, the algorithm for determining the RC filtering circuit parameters is proposed to ensure simultaneously the best conditions for switching the converter power switches and the implementation of continuous compensation of the engine reactive power, provided that the converter is operated with an increased power factor.</em><em></em></pre><strong><em>Practical value</em></strong>.<strong> </strong><em>The introduction of a simplified conversion system with a high power factor will create an automatic asynchronous drive system, through which it is possible to achieve energy conservation at the engine, converter and power system, with minimal capital investment in its production.</em> V.A. Borodai O.R. Kovalov O.Yu. Nesterova Copyright (c) 2020 V.A. Borodai, O.R. Kovalov, O.Yu. Nesterova https://creativecommons.org/licenses/by/4.0 2020-12-24 2020-12-24 2 8 16 10.15588/1607-6761-2020-2-1 Research of the non-sinusoidal loads impact on the operability of tap-changers contacts http://ee.zntu.edu.ua/article/view/220852 <p class="Abstract"><strong>Purpose.</strong> To establish quantitative indicators of the influence of non-sinusoidal loads on the parameters and operability of contacts of voltage control devices of transformers of power-consuming electrical installations</p><p class="Abstract"><strong>Methodology.</strong> In our research, we used the probabilistic-statistical methods to analyze the experimental findings. Experimental studies were carried out applying advanced software-based methods for processing, systematizing and visualizing the findings derived.</p><p class="Abstract"><strong>Findings.</strong> The analysis of the accident rate of transformers for power-consuming technological installations showed that adjustable transformers, in particular, on-load tap-changers, are in many cases the cause of failure in the operation of electrical installations. On the example of a switching device of the RNOA-110/1250 type, it was experimentally established that the non-sinusoidality of the current caused by abruptly alternating loads, in combination with an increase in the number of switchings, leads to an increase in the contact resistance, which significantly reduces the reliability and serviceability of contacts. </p><p class="Abstract"><strong>Originality.</strong> The dependence of the transient resistance of the contacts of the voltage control device under the load of the transformer on the degree of non-sinusoidality of the load current is obtained.</p><p class="Abstract"><strong> Practical value.</strong> The results of the work can be used in the development of new designs of on-load tap-changers for special purpose operation under conditions of load fluctuations. In particular, the work is aimed to increase the reliability of on-load tap changers contact systems, as well as in the study of the operating conditions of network and furnace transformers in power supply systems of energy-intensive technological installations.</p> V.V. Zіnovkin O.V. Blyzniakov Copyright (c) 2020 V.V. Zіnovkin, O.V. Blyzniakov https://creativecommons.org/licenses/by/4.0 2020-12-24 2020-12-24 2 17 23 10.15588/1607-6761-2020-2-2 Method of calculation of steady-state processes in electrical circuits http://ee.zntu.edu.ua/article/view/220855 <p class="a"><strong>Purpose.</strong> Development of a method for calculating established periodic processes of complex shape</p><p class="a"><strong>Methodology.</strong> Polynomial approximation of functions, numerical methods for solving integro-differential equations, mathematical apparatus of matrix algebra, computer programming and methods of electric circuit theory are used.</p><p class="a"><strong>Findings. </strong><strong> </strong>As a result of modification of the known method for calculating transient processes, a method has been developed that allows you to directly perform the calculation of steady-state periodic processes. This will reduce the time of computer simulation of electrical processes in linear electrical circuits. An example of using the proposed method is shown. Based on the developed method, a computer program for calculating the steady-state process in the model circuit is worked out. This example shows a 45% reduction in CPU time compared to the use of known methods.</p><p class="a"><strong>Originality</strong><strong>. </strong> Processes in electrical circuits are described by integro-differential equations. The approximation of functions of current derivatives to time by series on orthogonal Tchebyshev’s polynomials is used in their solution.When approximating functions, Chebyshev polynomials have uniform error in the whole range of argument change. It is advantageous stand out them from a number of other orthogonal functions. The proposed method uses a polynomial approximation not of the solution function itself, but of its derivative. The function itself is obtained with the help of integration operation. This operation has a small margin of error compared to the differentiation operation. The direct calculation of the steady-state periodic process is achieved by taking the initial conditions for currents and their derivatives at the beginning of the period as the values of the same functions at the end of the period. In the proposed method, integro-differential equations of state are transformed into linear algebraic equations. A method for creating a unified system of linear algebraic equations is proposed. The solution of this system allows you to perform directly the calculation of steady-state periodic processes.</p><p class="a"><strong>Practical value</strong> The developed method opens a new possibility of using a diverse apparatus of the electric circuits theory to work with images of currents. Based on this method, a universal software package is developed for calculating steady-state periodic processes in electrical circuits of arbitrary complexity. This will reduce the CPU time for modeling complex circuits.</p> D. Patalakh S. Tykhovod Copyright (c) 2020 D. Patalakh, S. Tykhovod https://creativecommons.org/licenses/by/4.0 2020-12-24 2020-12-24 2 24 31 10.15588/1607-6761-2020-2-3 Improvement of the evaluation method of calculation of power losses in power transformer http://ee.zntu.edu.ua/article/view/220859 <p class="Abstract"><strong>Purpose. </strong>The purpose of the work is to perform analytical analysis of methods for calculating power losses of a power transformer and to improve the estimation method of calculation to increase the accuracy of calculating power losses on the example of an industrial power transformer.</p><p class="Abstract"><strong>Methodology.</strong> Analytical and calculation method was used to determine power losses in the power transformer.</p><p class="Abstract"><strong>Findings. </strong>Analysis of the main power losses of power transformers is an important task to determine the optimal conditions for their operation. Analytical analysis of transformer power loss calculation methods is carried out. The relative contribution of different types of power losses is shown. The calculation of energy losses of the power transformer TM 1000/10/0.4 is performed. The losses of active and reactive energy of the transformer are determined. The efficiency of the power transformer is calculated. A generalizing formula for determining the efficiency of the transformer is proposed.</p><p class="Abstract"><strong>Originality. </strong>On the basis of the analytical analysis of methods of calculation of power losses of the power transformer the estimation technique is improved and calculation of losses of active and reactive energy of the industrial power transformer TM 1000/10/0.4 is carried out. A new generalizing formula for determining the efficiency of a power transformer, which takes into account the operating time of the transformer at maximum load, is proposed.</p><p class="Abstract"> <strong>Practical value.</strong> The estimation method for calculating the power losses of an industrial power transformer under load is improved, in which a generalizing formula for determining the efficiency of a transformer is applied. The proposed technique simplifies the calculations, reduces the estimated time to determine the operating parameters of the power transformer with the required accuracy. The proposed technique was tested on the example of the power transformer TM 1000/10/0.4. It is shown that with increasing maximum load time, the efficiency of the transformer increases and asymptotically approaches the maximum value. </p> O.S. Pidlisniy O.S. S.P. Lushchin Copyright (c) 2020 O.S. Pidlisniy O.S., S.P. Lushchin https://creativecommons.org/licenses/by/4.0 2 32 39 10.15588/1607-6761-2020-2-4