ISSN 2223-0858 (Online) Subject: theoretical and applied sciences, technology and industry in the field of energy and automation Year established: 2009 Founders: National University of Life and Environmental Sciences of Ukraine Published 4 times a year Media identifier R40-02287. The National Council of Television and Radio Broadcasting of Ukraine Decision No. 1796 of 21 December 2023, protocol No. 31. Speciality DAK: Technical Sciences Languages of the publication: Ukrainian, English Address: Heroiv Oborony st., 12, Kyiv-03041, Ukraine Phone: +38 044 527 85 22 Indexed in the following international scientometric databases: Google Scholar AGRIS MIAR BASE ResearchBib DRJI Ulrichsweb
Національний університет біоресурсів і природокористування України
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The influence of stator winding resistance imbalance of an induction motor: evaluation of phase current asymmetry
Asymmetry of the active resistances of stator windings occurs in approximately 30 % of repaired induction motors operating in power complexes of seaports, industrial enterprises, and ships. The resistance asymmetry causes current imbalance in the windings even under symmetrical supply voltage. In a non-symmetrical network, the asymmetry of active resistances can both increase and decrease the current asymmetry coefficient. The use of the Mathcad system enables the calculation of the current asymmetry coefficient depending on the deviation of the supply voltage, variation of stator winding resistances, load current, and supply frequency. Key words: induction motor, active resistance asymmetry, voltage asymmetry, current asymmetry coefficient
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Investigation of spectra and of aggregation of vanadium phtalocyanine molecules in two-component solutions
It was studied the electronic spectra of vanadium phtalocyanine dye molecules in diluted and concentrated solutions as well as in low- and high-polarity solvents. In diluted low-polarity solvent VOPc molecules exist in monomer state, whereas dye molecules concentration increase leads to appear of dimer formation. It was shown that using of mixed acid-water solvent is an effective approach to controlled aggregation of dye molecules. Main parameters of the influence on VOPc aggregation are concentration of water ingredient and associates “growth” time. In a concentrated high-polarity solvent, the dye molecule is in the form of a monocation solvated by solvent molecules and unable to interact with other dye ones. In this case, it is just the monomolecular absorbance spectrum that is characteristic for the solution. As water is added, the dye molecular interaction becomes possible due to the solvatic shell destruction, and association of organic molecules occurs. In our case, this results in the appearance of a broad 980 nm band in the absorbance spectrum. Using acid-water mixtures and varying the water concentration therein, the dye aggregation process can be controlled as well as the number of molecules in an aggregate. So the appearance of absorbance bands at 775 and 690 nm is observed which can be attributed to the formation of sandwich-type dimers (H-dimers). As the water concentration increases, large dye aggregates are formed. At high water concentrations, micro-scale single crystals may grow. The “growth” process can be observed in absorbance spectra as the appearance of the 980 nm band and its further intensity increase, long-wavelength shift and broadening. Above features demonstrate an approach to size-controlled preparation of dye molecules aggregates in polar – non-polar solutions mixture for farther use in photovoltaic and sensors applications. Key words: nano-size organic dye crystals, association of dye molecules, enhancement of electronic properties of aggregated dye molecules, seft-assembling of molecules
Comprehensive assessment of power quality in a low-voltage node with distributed generation and energy storage: evidence from field monitoring
The objective of this study is to conduct a comprehensive assessment of power quality parameters in a low-voltage node incorporating photovoltaic modules and an energy storage system, based on long-term field monitoring. The methodology involved analyzing time series of voltages, currents, active power, power factor, and total harmonic distortion recorded with a 15-minute resolution during the period September 2024 – March 2025. Data were segmented according to import and export modes of energy flow, resampled, and subjected to event-based detection of intervals deviating from EN 50160 and IEEE 519 standards. The results demonstrated that voltage consistently remained within permissible limits, whereas approximately 81% of measurements indicated current harmonic distortion exceeding 5%. The absolute power factor was not lower than 0.9 in 90% of cases, but declined to 0.85–0.90 in nearly 10% of intervals, primarily due to harmonic distortion and reactive power exchange. Moreover, the analysis confirmed the high stiffness of the supply network, which accounts for the stability of voltage parameters despite pronounced current harmonics. The findings underline the necessity of implementing active or passive filtering measures to mitigate harmonic distortion and maintain power factor stability. Key words: power quality, harmonic distortion, power factor, grid stiffness, short-circuit capability, low-voltage networks, municipal facilities
Improving the efficiency of a photovoltaic converter using the maximum power point tracking method
Methods and models of power consumption control systems for energy generation by solar photovoltaic converter (SPC) is an urgent task of finding the maximum power point (Maximum Power Point Tracking, MPPT) to increase efficiency. The results of mathematical numerical modeling in the MATLAB environment and experimental research using the physical model of SPC confirm the effectiveness of the developed control system. The input conditions included variable insolation, which was specified as a combination of two sinusoidal signals with an additional restriction within 200–1200 W/m², which allows modeling dynamic weather conditions, for example, the passage of clouds or partial shading. During the simulation, the voltage and current on the load were calculated through the conditional linear equivalent of the SPC taking into account the load resistance, which was changed according to the Perturb and Observe (P&O) algorithm. The developed system provides maximum power support throughout the entire simulation period, which confirms the practical value of the system for controlling SPC in energy systems. Key words: solar photovoltaic converter, resistance, maximum power point, mathematical model, perturb and observe
Research on the influence of frequency control methods on the energy efficiency of an automated electric drive of a pumping station
Pumping units are widely used for pumping various liquids, and most of all in water supply and drainage systems. Water consumption is a random function of time during the day (day, evening, morning) and depends on the season (summer, winter or spring). The efficiency and cost-effectiveness of cold and hot water supply, heating, drainage and water treatment enterprises of cities, urban and rural areas can be significantly increased through automation and the introduction of regulated electric drives. The article considers methods for increasing the energy efficiency of an automated electric drive of a pumping station, developed on the basis of a frequency converter using a PID regulator and an MRS controller. Existing technologies for regulating pump performance, such as the use of throttle valves and frequency converters (FCs), are analyzed. To study the impact of frequency regulation with a PID regulator and a digital twin on the energy efficiency of pumping units, a simulation model has been developed in the Matlab application package. The conducted studies show that the use of frequency control ensures the maintenance of the required technological parameters of the hydro network, reducing energy consumption compared to throttling with an unregulated pump drive, since operation at constant speeds leads to significant energy losses, especially in partial load modes. The use of an MPC controller allows you to improve the quality of the regulation process compared to a PID regulator, thereby increasing energy efficiency, anti-cavitation effect, and predictive diagnostics of defects reduces unplanned downtime. The potential for reducing energy consumption and improving the efficiency of pumping stations when using such methods has been assessed. The main advantages and disadvantages of frequency control, as well as the prospects for the development of these technologies in the context of energy saving, have been identified. Key words: automated electric drive, water pumping station, frequency control, MPC, digital twin, PID regulator, energy efficiency
Intelligent system for monitoring and forecasting the state of electrical equipment based on Microgrid
The concept of building an intelligent system for monitoring and forecasting the technical condition of electrical equipment within a decentralized energy system of the Microgrid type is considered. The architecture of the Predictive Maintenance (PdM) system is proposed, based on the use of sensor networks, Internet of Things (IoT) technologies, artificial intelligence (AI) and big data analytics (Big Data). A mathematical model for assessing the technical condition of electric motors is developed, which takes into account changes in the main electrical and mechanical parameters (current, voltage, temperature, vibrations, speed). The structure of the PdM process is proposed, which includes the stages of collecting, processing, analyzing data and forming predictive solutions based on machine learning algorithms. Key words: Microgrid, Predictive Maintenance, monitoring, electric motor, artificial intelligence, Internet of Things, Big Data, modeling, technical condition, energy efficiency
Experimental study of environmental factors' impact on surface leakage currents of high-voltage support insulators
Ensuring the reliability of high-voltage insulation systems is critical for the safe and efficient operation of power equipment. Surface leakage currents, formed under the influence of atmospheric and anthropogenic factors, accelerate the aging of insulation materials, reduce their dielectric strength, and increase the risk of emergency failures. Particular attention is given to the combined impact of relative humidity, temperature fluctuations, surface contamination, and wind speed, which together create highly unfavorable conditions for the operation of insulation systems and necessitate the implementation of automated approaches to monitoring and managing their condition. The aim of this work is to experimentally determine the influence of key climatic and anthropogenic factors on the leakage currents of support insulators, to assess the relative contribution of these factors, and to construct generalized graphical dependencies. The results obtained can be used to predict the performance of insulation systems and to develop automated methods for optimizing the operating modes of power equipment. The research was conducted on IOS-35-1000 UHL insulators operated at substations in the central region of Ukraine. It was found that the dominant influencing factors are relative humidity (30%), negative temperature difference (25%), and surface contamination (20%). Absolute humidity, duration of moisture exposure, and wind speed have a secondary effect on leakage current, with wind partially reducing surface conductivity. The experimental graphical dependencies reflect the dynamics of conductive layer formation under various moistening conditions. Critical operating conditions for insulation systems arise when high humidity, negative temperature differences, and the presence of a hygroscopic contamination layer are combined. The results obtained can be used to predict the reliability of insulation structures and to improve automated insulation condition monitoring systems. Key words: high-voltage insulator, leakage current, surface contamination, atmospheric factor, experimental study.
Speed optimization of positional electric drives using the maximum principle
The performance quality of many technological processes depends to a large extent on the inertial properties of executive devices. Positional electric drives with servomotors, which have integrating properties, are widely used as executive devices of automatic control systems. Optimizing the speed of such electric drives makes it possible to improve the quality of technological processes, reduce dynamic adjustment errors caused by the influence of the inertia of the executive device. The maximum principle is a convenient means of determining the optimal control law as a function of phase coordinates, that is, a means of synthesizing optimal regulators in closed systems, and a function of time, that is, a means of finding optimal software controls in open systems, which are positional electric drives with relay control. The purpose of this work is to substantiate the application of the maximum principle for the problem of optimizing the speed of positional electric drives and to find an analytical solution to this problem. Key words: optimal control, maximum principle, electric drive, optimality criterio
Influence of voltage deviations on the drive characteristics of working machines with dc motors of independent and parallel excitation at Mc=const
Voltage deviation in DC motors leads to losses that have an electromagnetic and technological component. Studies on the influence of voltage deviation and asymmetry on the technological and energy characteristics of working machines and mechanisms with an asynchronous electric drive have shown that when they deviate, productivity decreases and specific energy consumption increases. However, there are no studies on the influence of voltage deviation on DC electric drives. The purpose of the study is to establish the influence of voltage deviation in electric drives with DC motors of independent and parallel excitation on the technological and energy characteristics of working machines with a static resistance moment independent of angular velocity. When the voltage deviates, the angular velocity of DC motors of independent and parallel excitation changes, which causes a change in the productivity of the working machine. In DC motors of independent excitation, the dependence of the productivity of the working machine on the voltage change is linear, and in DC motors of parallel excitation, the productivity of the working machine during voltage deviation changes according to a complex algorithm. When the voltage deviates, the constant and variable power losses in the DC electric motor change. It is proposed to conduct an energy assessment of a DC electric drive based on specific electricity consumption. The study of the influence of voltage deviation on the energy characteristics of working machines with a constant moment of static resistances, which are driven by DC motors of independent and parallel excitation, was carried out. It was established that with a decrease in voltage, specific electricity losses increase. Key words: DC motor with independent and parallel excitation, voltage deviation, specific power consumption
Method of structural synthesis of the power supply network of critical infrastructure facilities
At present, the urgent problem is to enhance the structural resilience of energy networks against their constant destruction caused by air attacks. The article examines the issue of integrating decentralized generation sources to ensure the energy autonomy of critical infrastructure facilities. The purpose of the study is to improve the structural resilience of energy supply networks for critical infrastructure based on the optimal integration of renewable energy sources, biogas plants, and energy storage systems. To achieve this objective, the problem statement was formulated, and a modified branch and bound method was proposed for its solution. An algorithm for solving the multi-criteria optimization problem of energy network structures was developed. The main results confirm that the optimal structural integration of solar and wind generation, biogas plants, and batteries makes it possible to cover critical loads under forecasted conditions. The implementation of such systems significantly increases the structural resilience of energy systems and creates conditions for the sustainable development of energy-independent communities. Key words: structural stability, power grid, solar, wind generation, energy storage, biogas plants, optimization
Analysis of parallel operation of autonomous wind power plants with asynchronous generators
The article presents an analysis of modern studies dedicated to the parallel operation of autonomous wind energy systems with asynchronous generators. The advantages and limitations of using asynchronous machines in decentralized power systems are considered, particularly their simple design, reliability, and cost-effectiveness. Various approaches to organizing parallel operation are analyzed, including the features of ensuring and maintaining self-excitation, the use of capacitor banks, connection schemes for generators of different capacities, and methods of voltage and frequency regulation. Special attention is paid to the role of mathematical and simulation modeling, as well as experimental studies, which make it possible to evaluate the efficiency of systems under variable operating conditions. The prospects of applying controllers, especially those based on fuzzy logic, to enhance the stability and efficiency of autonomous power systems are also discussed. Based on the analysis, directions for further research are identified, particularly the need for a comprehensive consideration of transient processes, wind speed fluctuations, and the impact of load characteristics on the operation of parallel-connected generators. Key words: renewable energy sources, wind energy, wind power plant, asynchronous generator, parallel work, autonomous work
Development of new heat exchanger design for the use of exhaust gases of ice in cogeneration plants. heat calculation
A new design of a heat exchanger for the use of exhaust gases of an internal combustion engine, which is part of a cogeneration plant, is proposed. This exchanger differs from traditional designs by the presence of compact bundles of small diameter pipes with no gaps between adjacent pipes in the longitudinal direction of the gas coolant movement. A method of heat calculation of heat exchanger-utilizer has been developed, which makes it possible to determine the dimensions of heat exchanger. The results obtained have been analyzed and it has been shown that the new design of heat exchanger-utilizer has a number of advantages compared to the known designs of shell-and-tube heat exchangers. It has been found that the new design of heat exchanger improves the mass-dimensional indicators of heat exchanger-utilizer compared to known designs and can be used in the development of cogeneration plants based on internal combustion engines. Key words: shell-and-tube heat exchanger, method calculation, heat calculation, design, cogeneration plant, tube bundle
Luminescent labeling of leaves for remote monitoring of plants
Luminescent markers are attracting increasing attention as a means of monitoring plant health due to the development of modern technologies for collecting, processing, and storing data necessary for precision agriculture. The combination of optical characteristics (reflection and emission of light) of markers (phosphors) and plant leaves allows remote monitoring, which contributes to the automation of the plant growing process. At the same time, the choice of the phosphor and the method of its application to the plant remains a relevant area of scientific research. In this work the results of the study of optical characteristics such as: diffuse reflection, photoluminescence (PL), and PL excitation spectra of leaves "before" and "after" the application of suspensions of two types: phosphor + water and phosphor + water + PVA, where the phosphor was SrAl2O4:Eu,Dy powder, have been analyzed. It was found that the application of suspensions of both types increases the diffuse reflection of light by leaves in the entire visible region., Three PL bands were observed in the photoluminescence spectra of untreated leaves: one of low intensity with a maximum at 535 nm, and two intense bands with maxima at 685 and 740 nm. The latter two bands of red luminescence correspond to the emission of the molecules of chlorophyll a, while the band at 535 nm may be ascribed to the emission of carotenoids in the leaves. The application of the SrAl2O4:Eu,Dy+H2O suspension practically does not lead to a change in the spectrum of intrinsic "red" PL of the leaves in the region of 625–825 nm. At the same time, for leaves coated with the SrAl2O4:Eu,Dy+H2O+PVA suspension, there is an increase in the luminescence intensity in the region of 450–650 nm, compared to the intensity of the band at 685 nm. The relative intensity of the PL band at 740 nm, however, decreases. It has been demonstrated that the PL spectra of the samples are sensitive to changes in the PL excitation wavelengths, ghat allows for selective excitation of the photoluminescence of the phosphor label and chlorophyll a contained in the leaf. The obtained results indicate the possibility of using the optical properties of leaves treated with suspensions to collect information about the condition of the plant, with the aim of applying the Internet of Things (IoT) concept in crop production. Key words: chlorophyll, light absorption, luminescent marker, photoluminescence
Comprehensive approach to energy efficiency assessment of induction furnaces under unstable power supply
A comprehensive approach to evaluating the energy efficiency of induction furnaces under unstable power supply has been developed, integrating electromagnetic, thermodynamic, and stochastic models. The influence of power grid parameter fluctuations on electromagnetic field penetration depth, eddy current distribution, and temperature gradients in the melt has been investigated. The nonlinear nature of heating power dependence on voltage and frequency deviations has been established. A mathematical model for probabilistic assessment of energy losses under various types of power supply anomalies has been formulated. A methodology for calculating integral energy efficiency indicators has been developed, including the coefficient of variation of efficiency and the probability of ensuring a minimum acceptable efficiency level. A phenomenological analysis of the relationship between power quality indicators and thermodynamic characteristics of the melting process has been conducted. Theoretical principles for constructing adaptive control systems for induction furnaces based on predictive models of power grid fluctuations have been substantiated. The research results create a theoretical basis for developing intelligent control systems for induction melting units capable of ensuring an optimal balance between energy efficiency and product quality. Key words: induction furnace, energy efficiency, unstable power supply, electromagnetic field, stochastic modeling, adaptive control, metallurgical processes
Research on the influence of the specific density of the raw material fermented in a biogas reactor on heat distribution
Biogas technologies are becoming increasingly widespread in industrial and domestic facilities. However, the profitability of biogas production depends on the energy consumption to support the fermentation process, so it is necessary to conduct research aimed at reducing energy costs for heating and mixing the raw material being fermented. Raw materials with different physicochemical compositions are used for fermentation, which significantly affects energy costs. The aim of the work is to study the influence of the specific density of the raw material being fermented in a biogas reactor on the energy costs for mixing and changing the Reynolds criterion. The paper presents the constructed mathematical model and research results. The research considered a wide range of changes in the specific density of the substrate from 750 to 1500 kg/m3. According to the research results, graphical dependences of the change in the Reynolds criterion, heat transfer coefficient and heat transfer coefficient were obtained, depending on the change in the specific density of the raw material and the frequency of rotation of the working body of the mixing device. It has been established that the change in the criterion and coefficients depending on the change in the density of the raw material occurs according to a linear law. The results obtained will allow setting a rational rotation frequency of the mixing device in which the heating device is located from the point of view of energy consumption for the processes of mixing and electrical heating of the raw material. Key words: Reynolds criterion, heat transfer coefficient, heat transfer coefficient, specific density of raw materials, anaerobic digestion, mixing
Experimental study of heat and mass transfer in solid dispersed materials during vapor-depression drying
The intensity of technological processes involving dispersed materials is most often limited by the speed of internal mass transfer. The vapor-depression drying method, developed by scientists of the Institute of Thermal Physics of the National Academy of Sciences of Ukraine, allows for the intensification of internal moisture transfer and thus creates the prerequisites for accelerating the drying process. The vapor-depression drying process has been considered in detail in the literature for the case of drying a capillary-porous body - sheet plaster. The purpose of this study is to consider the effect of a vapor-permeable shell on the intensification of internal mass transfer during the drying of a capillary-porous colloidal body - viscose fiber. In experimental studies, ordinary knitted shells and shells with increased density, as well as cloth and paper shells were used. The absence of a clearly defined period of constant drying speed was recorded, which indicates a low intensity of moisture transfer in the material. The highest values of the drying speed are achieved when using a single knitted shell, the lowest - when dewatering the fiber in a cloth shell. The obtained experimental data can be used to develop effective methods for controlling the drying processes of solid dispersed bodies. Key words: vapor-depression drying, solid dispersed bodies, vapor-permeable shell, drying rate
Experimental study of the operation of a Stirling engine with a solar concentrator and an additional energy source
The efficiency of solar energy is limited by the natural variability of solar radiation levels. The Stirling engine is a promising solution for solar energy systems, especially when using concentrators, such as a Fresnel lens. The main obstacle to the widespread implementation of such systems is their dependence on the stability of solar radiation. The purpose of the research is to create an experimental stand and methodology to determine the feasibility of using an additional energy source (electric heater) to prevent the shutdown of the Stirling engine, which uses concentrated solar radiation using a Fresnel lens as the main source of heat. The paper presents an experimental study of the Stirling engine, which includes the study of the effect of variable insolation and the assessment of the efficiency of using an electric heater as an additional energy source (AES) to improve system stability. A series of experiments was conducted with different durations of insolation interruption (20, 40 and 60 s). The results confirmed the ability of the AES to prevent engine shutdown and increase the total energy produced by 47 %, 90 % and 130 % for the respective intervals. Key words: Stirling engine, Fresnel lens, additional energy source, power stabilization, solar energy, experimental stand
Research on the efficiency of using solar tracker in urbanized conditions
In the context of rising energy prices and the need for energy independence, the development of renewable energy sources, in particular solar, is becoming particularly relevant. Solar power plants (SPPs) on the roofs of multi-story buildings are a promising solution for urban environments, where the area for ground-based installations is limited. To maximize electricity production from a limited area, it is critical to use technologies that increase system efficiency. Solar trackers, which automatically orient photovoltaic modules perpendicular to the sun's rays, are one of the most effective tools for achieving this goal. The main objective of this study is to analyze the technical and economic feasibility of implementing different types of solar trackers for a solar power plant located on the roof of a typical nine-story building. The objectives are: • to conduct a comparative analysis of single-axis (HSAT, VSAT, tilted axis) and dual-axis trackers; performing technical generation calculations and assessing the impact of key factors such as spatial constraints, shading and temperature; • assessing economic feasibility, taking into account initial investments and payback; • providing sound recommendations for two specific locations in Ukraine: Zaporizhia (south) and Ivano-Frankivsk (west). Key words: photovoltaic module, solar tracker, single-axis trackers, temperature, insolation, multi-storey building
Modeling of an energy efficient fan installation based on an adjustable electric drive with a fuzzy logic regulator
Centrifugal fan installations are the most common in various spheres of production, both light and heavy industry. More often, centrifugal fans are installed as unregulated electric drive installations, especially low capacity. But there are a lot of technological equipment, especially in the production sphere, where it is necessary to regulate the productivity of fans. Moreover, regulation is carried out in a fairly wide range. Electrical drive of centrifugal fans is usually realize on the basis of an asynchronous short -circuited engine. To adjust the supply of such fan is carried out the adjusting of the speed rotation of the engine using the frequency converter Among the known ways of regulating the efficiency of fan installations, namely throttling, change of the angle of installation of blades, using of guiding machines, regulating of the number of rotations of the fan shaft is the most effective way. In modern conditions, the change of the fan shaft rotation is carried out by changing the drive shaft rotation of drive engine. In the article is considered the issue of increasing the energy efficiency of fan installations by using an adjustable electrical drive with using the regulator, built on the principles of fuzzy logic. The mathematical model of the system in the Matlab application package has been developed, computer modeling has been carried out and the benefits of the proposed approach are shown in comparing to the traditional methods of regulation. Key words: fan installation, energy efficiency, adjustable electrical drive, asynchronous engine, sub- regulator, fuzzy logic controller, Matlab
Study of the influence of changes in the motor speed on the technological characteristics of a feed pellet mill
The influence of changes in the motor speed on the pellet mill performance, as well as on the technological and energy parameters of feed pellet mills is investigated. The dependencies between the motor speed and such indicators as productivity and general characteristics of the equipment operation are revealed. Productivity increases with increasing speed up to a certain point, but for most feeds, there is a stabilisation or even a decrease in productivity after reaching the maximum level. Different feeds have their own optimal characteristics: soybeans and a mixture of cereals are better suited for pellet mills due to their higher productivity, while barley has a much lower productivity, so it is necessary to make adjustments to the technological process (change the structure, moisture content or other parameters). Feed moisture content in the range of 9-9.6% contributes to high productivity, while barley has the lowest productivity even at optimal moisture content, which may be due to its physical properties. The research allows us to determine the optimal operating modes of the pellet mill, which achieve the production of high-quality feed with minimal energy consumption. Further research can be aimed at studying the influence of other parameters, such as temperature and the addition of various components. Deviations in the change in the motor speed lead to a disruption in the stable flow of technological processes, a decrease in product quality, a reduction in the service life of electrical equipment, an increase in electricity losses in power consumption systems, and the creation of emergencies that can threaten human safety [1]. Key words: feed pellet mill, electric drive, performance, frequency converter, network analyser
Research and analysis of testing nonlinear overvoltage limiters for high-voltage electrical networks
Research and analysis of nonlinear surge arresters (NSAs) for high-voltage electrical networks is a key process for assessing their effectiveness, reliability, and compliance with standards, which includes: determining NSA characteristics, conducting laboratory and field tests, simulating their operation, analyzing the results, and comparing them with regulatory requirements to ensure the protection of networks from overvoltages. The paper provides a detailed analysis of the testing of AZBD series surge arresters, as well as a study of the surge arrester for a 220 kV high-voltage electrical network of the type OPN-P-220/158/10/2 surge arrester with residual voltage values of 510 kV and 574 kV at a lightning impulse current of 8/20 μs with amplitudes of 10 kA and 20 kA, respectively, and 402 kV and 419 kV at a switching current pulse of 30/60 μs with an amplitude of 500 A and 1000 A, respectively. This article analyzes the testing of surge arresters with short-circuit currents, describes the charge transfer characteristics and energy capacity of surge arresters, presents new tests in accordance with DCU EN 60099-4:2016, and verifies the characteristics of surge arresters after applying bending loads and testing for resistance to environmental influences. A brief description of the structural and basic electrical diagram of the test setup used in the laboratory of electrical installations and power supply systems for testing surge arresters, valve arresters, vitelline discs, and spark gaps of various voltage classes is provided. The volt-ampere characteristics of the surge arrester, the dependence of the residual voltage on the impulse current, and the dependence of the leakage current on the alternating voltage were constructed. Additional graphs were also constructed for the OPN-P-220/158/10/2 surge arrester, an approximation graph (U = a·Ib) with the obtained equation, a graph of dynamic resistance R = U/I as a function of current, and the dependence of residual voltage on the conditional pulse energy. These graphs together provide a complete picture. In particular, the approximation describes the general mathematical relationship; the dynamic resistance R(I) shows the effectiveness of the limiter; the relationship between the residual voltage and energy U(E) allows us to evaluate the behavior under pulses of different nature. Key words: electrical networks, nonlinear surge arresters, lightning discharge, impulse current, residual voltage, pulses
Development of software for controlling the movement of jib crane mechanisms
The article provides an overview of software products from leading developers of software for the operation of cranes. The statement and solution of the problems of optimal control of the movement of the mechanisms of load hoisting and slewing the jib crane in the acceleration and braking modes are presented. Calculations were carried out for three quadratic integral quality criteria, which reflected the driving factors and their higher derivatives in time up to the second inclusive. The laws of change of the driving elements (angular velocities of the drives of the mechanisms) were obtained, which ensure the implementation of optimal control. The software "Optimal control of the movement of jib crane mechanisms" was developed, which allows using frequency-controlled drives of both mechanisms to implement optimal control in practice. A description of the communication settings between frequency converters and a computer with the developed software via a serial communication port is presented. The sequence of actions of the user of the software product is shown in order to calculate the optimal laws of motion, their visualization and transmission of control commands to frequency converters to perform tasks of optimal control of the movement of mechanisms. Key words: hoisting crane, software, optimal control, development
Dynamics of a double-head streamer in air: numerical analysis for an inter-electrode gap of 0.3 cm
The work investigates the dynamics of a double-headed streamer discharge in air at 14 kV using hydrodynamic modeling. Numerical simulations in COMSOL Multiphysics (2D axisymmetric geometry, finite element method) revealed significant differences in the development of positive and negative streamers in a 0.3 cm gap: the negative streamer shows high initial velocity (0.4 cm/ns) that rapidly decreases, limiting its maximum propagation distance (0.15 cm), while the positive streamer accelerates over time (up to 0.0378 cm/ns), covering a greater distance (0.14 cm) due to higher electron density (up to 3.34×10²⁰ 1/m³) and more intense electric field (375×10⁵ V/m vs 119×10⁵ V/m for the negative one). The obtained results confirm the model's ability to accurately reproduce spatiotemporal evolution of streamers, which is crucial for high-voltage device development and breakdown analysis. The study was conducted at 760 Torr with a time step of 0.05 ns over 3.75 ns. Key words: double-headed streamer, streamer discharge, numerical simulation, air gap, interelectrode gap, COMSOL Multiphysics, hydrodynamic model, positive streamer, negative streamer, air breakdown, high-voltage discharge
Optimization of glass furnace heat recovery exchanger parameters
The research results on the efficiency and optimization of glass furnace heat recovery exchangers parameters using complex methods, including exergy analysis methods and optimization algorithms used in statistical experimental design theory are presented. Two types of heat recovery exchangers using the heat from exhaust gases of glass furnaces were investigated. This is an air-heating heat recovery exchanger (end recuperator) designed to preheat cold air before it enters the furnace regenerator, and a water-heating heat recovery exchanger with a staggered and corridor arrangement of pipes in a bundle, which is used in schemes for heating water in heating systems. To optimize the heat exchange surface parameters of heat recovery exchangers, a complex methodology has been developed based on an exergy approach and the canonical transformation method used in statistical experimental design theory. Within the framework of the exergy approach, exergy criteria are used that can serve to evaluate the exergy efficiency of heat recovery exchangers and as optimization objective functions (response functions) when solving optimization problems. The canonical transformation method is used as the optimization algorithm, which allows obtaining a graphical interpretation of the optimum region for the response function in the form of a series of contour curves on a plane. Functional dependencies of the efficiency evaluating criteria for air-heating and water-heating heat recovery exchangers on their main parameters in canonical form have been obtained. Graphs of specified dependencies and graphical interpretations of the optimum regions for response functions are presented in the form of a series of contour curves on a plane. A detailed study of response surfaces in the response function minimum region was conducted, and the optimal regions of geometric parameters for the heat exchange surface of air-heating and water-heating heat recovery exchanges were determined. When determining the intervals for changing parameters based on the optimal parameters exact values, the technological requirements for the heat exchange surface of heat recovery exchangers were also taken into account. The research conducted will serve to develop increased efficiency heat recovery systems.
Electroelastic bulk and normal shear waves in a layered-periodic medium of the type metal-piezoelectric-dielectric
A method for constructing dispersion relations for bulk and normal electroelastic shear waves propagating in layered-periodic media formed by repeating a "generating" metallized package consisting of a piezoelectric layer and a dielectric layer that has no electrical properties is proposed. As a result of the analytical calculations, dispersion relations for normal and bulk electroelastic shear waves were obtained. CdS or ZnO were considered as piezoelectric materials, and the dielectric layer was chosen with the parameters GaYIG. The obtained dispersion relations were numerically analyzed for different geometries and physical properties of the materials forming the "generating" package. . Numerical analysis showed that a feature of the obtained bulk wave spectrum is that in the range of changes in the wave number and circular frequency, the zone boundaries do not intersect. The spectrum of normal waves is localized in the transmission zones of bulk waves except for one dispersion curve. The influence of physical, mechanical and geometric parameters of the layers on the structure of the blocking and transmission zones has been studied, as well as the influence of the piezoelectric effect has been investigated. Based on the approach proposed in the works of M.O. Shulga, the problems of bulk and normal electroelastic waves are reduced to the study of the properties of the transmission matrices of the "generating" package of layers, through the elements of which the desired dispersion relations are expressed. In the work, it was possible, using the condition of metallization on the outer surfaces of the package, to write the dispersion relations through the elements of second-order matrices instead of the fourth, which allows simplifying the analysis of the dispersion equations. Key words: bulk and normal shear waves, periodic layered structure, piezoelectric, dielectric, transmission zones, bulk wave blocking zones
Theoretical study of the motion of material particles in centrifugal devices with curved blades and variable angle of their rise
In centrifugal scattering devices, the blades provide the necessary trajectory and speed of the particle in relative motion. The operation of scattering devices with straight blades has been sufficiently studied. From a theoretical point of view, it seems interesting to study the motion of a particle along a curved blade, when the angle of elevation of the particle increases from zero to a given value at the moment of its descent from the blade. The purpose of the study is to perform a comparative analysis of the motion of a particle along straight and curved blades, which provide a given angle of elevation of the particle at the moment of its descent from the blade. When a disk with a curved blade rotates, the particle performs a complex motion: translational due to the rotation of the disk and relative along the blade. To compile the differential equations of motion, it is necessary to find the absolute acceleration vector, which includes three components: acceleration in translational motion, acceleration in relative motion, and Coriolis acceleration. This vector is conveniently searched for in the projections onto the orthogonal surfaces of the accompanying trihedron of the translational motion curve, which for the rotational motion of the disk will be a circle. Generalized differential equations of particle motion in centrifugal devices along a curved blade with a variable lift angle have been derived. A comparative analysis of the kinematic parameters of motion for straight and curved blades has been performed. A comparative analysis of particle motion along straight and curved blades of a centrifugal scattering device has shown that a particle along a curved blade in the form of an arc of a circle of the specified length accelerates faster than along a straight one. Thus, replacing straight blades with curved ones allows achieving the same effect while reducing the angular velocity of disk rotation from 25 rad/s to 23 rad/s, i.e., the reduction is 8%. With an unlimited length of the blade in the form of an arc of a circle, the particle performs an oscillatory motion along it up and down with damping until it comes to a complete stop in the presence of friction. Key words: curved and rectilinear blades, differential equations, lift angle
Current state and prospects of energy-saving development of vegetable storage engineering systems in Ukraine and the world
Збереження свіжості та якості овочів є важливим завданням для аграріїв у всьому світі, включаючи Україну. На тлі зростання цін на енергоносії, енергоефективність систем зберігання овочів стає особливо актуальною. Тому сучасні технології зосереджуються на розробці енергоощадних інженерних рішень для овочесховищ, спрямованих на зменшення енерговитрат та екологічного впливу. Особливу увагу приділяють оптимізації умов зберігання, автоматизованим системам керування мікрокліматом та використанню відновлюваних джерел енергії. У статті розглянуто сучасні тенденції та перспективи розвитку енергоефективних інженерних систем для овочесховищ в Україні та світі. Наголошено на важливості оптимізації мікроклімату для збереження продукції та мінімізації енергетичних витрат. Дослідження базується на аналізі наукових публікацій, нормативних документів та аналітичних даних щодо вентиляційних, холодильних систем та автоматизації мікроклімату овочесховищ. Проведено порівняльний аналіз традиційних та сучасних технологій зберігання, включаючи застосування чисельного моделювання гідроаеродинамічних процесів (CFD) для оцінки ефективності систем підтримки мікроклімату. Визначено, що інтеграція відновлюваних джерел енергії (сонячних панелей, теплових насосів, систем акумуляції холоду) суттєво знижує енергоспоживання овочесховищ. Використання CFD-моделювання дозволяє оптимізувати параметри повітрообміну, температури та вологості, що сприяє зменшенню втрат продукції та оптимізації енергоспоживання. Аналіз сучасних технологій свідчить про зростаючу роль інтелектуальних систем керування мікрокліматом, що дозволяють автоматично регулювати параметри повітряного середовища та забезпечувати оптимальні умови для збереження овочів. Впровадження енергоефективних технологій зменшує операційні витрати та мінімізує екологічний вплив. Досліджено концептуальні підходи до підвищення ефективності зберігання овочів, що базуються на поєднанні CFD-моделювання, автоматизованих систем керування мікрокліматом та інтеграції відновлюваних джерел енергії. Впровадження цих підходів сприятиме покращенню якості зберігання продукції, зниженню енергоспоживання та збільшенню економічної ефективності овочесховищ. Подальші дослідження у сфері CFD-моделювання є важливими для вдосконалення технологій розподілу повітряних потоків, вологості та температури, що дозволить підвищити ефективність інженерних систем для зберігання овочів. Ключові слова: мікроклімат овочесховищ, інженерні системи овочесховищ, енергоефективність, CFD-моделювання, відновлювальні джерела енергії, вентиляція
Electrotechnological complex of plants energy-efficient irradiation in greenhouses
The electrotechnological complex of energy-efficient irradiation of plants in greenhouses is an important aspect in modern agro-industrial production, as it provides optimal conditions for plant growth and development, reducing energy consumption. This complex uses modern lighting technologies that allow for the effective use of natural and artificial lighting, optimizing its intensity and spectrum to ensure maximum photosynthetic effect. One of the main principles of energy-efficient irradiation is the use of light-emitting diode (LED) lamps, which makes it possible to regulate the light spectrum, adapting it to the specific needs of plants. These lamps have high energy efficiency and a long service life, which allows reducing electricity and maintenance costs. In addition, the use of automated control systems, such as light and temperature sensors, allows maintaining an optimal microclimate in greenhouses. Integration of such systems into agro-industrial complexes allows not only to increase yields, but also to reduce the impact on the environment due to the rational use of energy. The development and implementation of energy-efficient irradiation technologies in greenhouses is an important step towards the sustainable development of the agricultural sector, in particular in the context of climate change and increasing demand for environmentally friendly products. Key words: electro-technological complex, energy efficiency, plant irradiation, greenhouse, LED lighting, automation, agro-industrial production
Efficiency of carbon dioxide capture in a rotating packed bed with diifferent absorbents
One of the effective approaches to reducing CO₂ emissions is the use of liquid absorbents in various types of contact devices, particularly in centrifugal rotating packed bed (RPB) absorbers. This study presents a comparative analysis of chemical liquid absorbents (NaOH, MEA, piperazine) based on mass transfer efficiency, thermal and oxidative stability, regeneration energy demand, and economic feasibility. It was found that centrifugal contactors demonstrate a significantly higher volumetric mass transfer coefficient compared to conventional packed absorption columns, especially when using MEA. The influence of absorbent concentration and hydrodynamic parameters on mass transfer intensity was analyzed. The results show that piperazine, despite its higher cost, provides the best operational performance. The research offers a foundation for selecting absorbents considering both technical and economic parameters as well as mass transfer efficiency, aimed at compact and energy-efficient CO₂ capture systems. Key words: liquid absorbents, rotating packed bed, CO2 capture, mass transfer
Energy efficiency of heat pump continuous flow grain dryers
Grain drying is an energy-intensive stage of post-harvest processing, where the use of heat pumps is one of the methods to improve energy efficiency. The paper provides concise information on drying technology, types of dryers, and their features. Particular attention is paid to recirculation schemes of the drying agent, which reduce energy consumption by reusing the heat carrier. Modern approaches to integrating heat pumps into continuous flow grain dryers systems are discussed, enabling dual functionality: dehumidifying air in the evaporator and heating it in the condenser. The article proposes a methodology for assessing the energy efficiency of grain drying in heat pump continuous flow grain dryers. The study also analyzes the influence of the non-isenthalpic drying mode in continuous flow dryers, a key feature that differentiates them from chamber systems. Recommendations for optimizing drying parameters to reduce energy consumption and improve dryer efficiency are provided. The research findings may be useful for agricultural enterprises seeking to modernize post-harvest grain processing technologies. Key words: grain dryer, energy efficiency, recirculation, heat pump, flow-through dryers, chamber dryers, grain moisture