The aim of the work was parametric synthesis of vector sensorless (i. e. without speed sensor) control of an electric drive with an induction motor. The structure of the system is based on the application of an adaptive model for estimating the rotor flow coupling vector and velocity. The speed is estimated by the mismatch of the real stator current and the current value calculated in the model. Stability is guaranteed in this well-known structure, obtained on the basis of Lyapunov functions, but it remains problematic to calculate the parameters of regulators and an adaptive model to ensure high-quality dynamics of the system. For a vector control system of an induction electric motor without a speed sensor with an adaptive model, a linearized structure in a synchronously rotating coordinate system was proposed. This makes it possible to calculate control parameters using the modal control method to ensure quality indicators in each of the closed circuits of the system. Such parametric synthesis is based on the assumption that the flow coupling of the rotor is maintained constant, and therefore the mutual influence of the flow coupling and torque control channels can be neglected. The calculation of the parameters of control (regulators and the adaptation channel) is based on the method of assigning the roots of characteristic contour polynomials in such a way that each internal contour has a higher speed than the external one with respect to it. The method is approximate, but it makes it possible to take into account the main cause-and-effect relationships in dynamics and obtain simple calculation expressions. The simulation of the system was carried out using a simulation model that takes into account the digital software-algorithmic method for generating a microcontroller control signal, as well as electromagnetic processes under conditions of pulse-width modulation in an electric energy converter and an electric motor, the use of the values of the rotor flow coupling vector estimated by the model in coordinate transformations of the system, the formation of a spatial vector of the converter voltage. The analysis of the synthesized speed control system by the simulation method has confirmed the effectiveness of the proposed method of parametric synthesis and the acceptable accuracy of speed estimation.

Currently, transformer manufacturers are tasked with creating energy-efficient devices with a reduction of steel losses of up to 44 %. Appropriate theoretical developments are needed for its implementation. With a reduction of eddy-current losses, caused, for example, by reduction of decrease in the thickness of the magnetic conductor sheets, hysteresis losses simultaneously increase. A similar effect is caused by changing the size of the crystal grain of steel, thermomagnetic treatment and other technological impacts. In this regard, the exact determination of the components of total losses in steel is an urgent problem, the solution of which would minimize total losses. The article analyzes the expressions that determine the specific losses for eddy currents and hysteresis through the parameters of the magnetic circuit, and states that this technique is too complicated for engineering calculations. Since eddy current losses are proportional to the square of the frequency, and hysteresis losses are proportional to the frequency in the first degree, simple calculated expressions of eddy current and hysteresis losses have been obtained using the wattmetric method. Based on the fact that the dependence of the magnetization loss on the thickness of the magnetic conductor plates is a decreasing linear function, and the eddy current loss is an ascending parabolic function, an expression of the optimal thickness of the plates has been found, the implementation of which makes the losses of steel minimal. This information will make it possible to minimize total steel losses more effectively by varying the design parameters and the material of the magnetic conductor. It is shown that the charted idling losses of transformers manufactured by different manufacturers differ by more than 30 % and can be rounded and underestimated; therefore it is advisable to obtain this parameter as a result of an experiment (idling experiment).

The aim of the study was to evaluate the efficiency of an energy-and-technology unit based on a continuous furnace of a rolling mill with an option for hydrogen production. A brief analysis of hydrogen production technologies and the prospects of their application in metallurgy are presented. It has been determined that as for enterprises with the potential of thermal waste, the use of thermochemical technologies is promising for the production of hydrogen. The main aspects and features of thermochemical methods of hydrogen production are shown from the standpoint of choosing the number of stages of chemical reactions implementation and determining the thermodynamic conditions for their conduct. The conditions for the implementation of the copper-chlorine Cu–Cl thermochemical cycle were investigated, and a rational variant of its implementation has been determined, taking into account the use of thermal waste (secondary energy resources) of the heating furnaces of the rolling mill. The application of the evolutionary method made it possible, on the basis of the technological scheme (which had been previously developed and investigated, and consisted of an energy-and-technological installation as a part of a rolling mill of a heating furnace and a utilization gas turbine with external heat supply that maintains the regenerative component of heating the air oxidizer), to synthesize a scheme of an energy-and-technological installation with the inclusion of a technological unit implementing a hybrid thermochemical copper-chlorine Cu–Cl cycle for separating water into hydrogen and oxygen using thermal secondary energy resources and electricity generated by a utilization gas turbine installation. Mathematical model of the macro level has been developed. The conducted numerical test experiments have shown the high energy prospects of the developed energy-and-technology installation, the fuel utilization rate of which is in the range of 75–90 %. The coefficient of chemical regeneration of fuel energy for the test mode was 11.3 %. As a result of numerical research, the prospects of developments under consideration in terms of the development of hydrogen production technologies with the use of thermochemical cycles and the high-temperature thermal secondary resources have been proved.

The paper presents studies on saving energy resources by creating conditions and introducing modern energy-efficient technologies and equipment into production activities that allow to develop the production and use of local fuels, including the use of briquetting of combustible municipal and industrial waste. The purpose and objectives of the work are to study trends and analyze the problems associated with the processing and use of various types of combustible waste generated and accumulated in industrial and agricultural enterprises, as well as in the field of housing and communal services. The main directions of national sustainable development strategy concerning energy and resource saving and  rational use of natural and secondary resources are considered in the paper. Methods for briquetting  multicomponent compositions of combustible wastes with the possibility of obtaining solid fuels have been studied. An innovative production technology developed by the authors is described that makes it possible to process waste products by briquetting with the use of various binders.  The results are presented  and the analysis of the conducted experimental studies is carried out in accordance with the theory of experiment planning for multicomponent systems, taking into account phase equilibria. A qualitative assessment of the component composition of the briquetted fuel, which ensures  the highest density of the briquette and effective performance,  is carried out taking into account of the moisture content of the multicomponent mixture.  Qualitative indicators of the produced two- and three-component fuels  have been determined using differential thermal analysis on the MOM-1500 derivatograph, which make it possible to identify phase transformations and chemical reactions occurring during heating. Comparative analysis of qualitative indicators has permitted to draw conclusions about the possibility of using the developed fuel compositions in operated fuel combustion plants.  

The results of the study of heat and mass transfer in the processes of heat treatment and drying processes of thermal insulating materials when the values of the Biot heat exchange criterion are less than one and the main factor is the interaction of the evaporation surface of the material with the environment (external problem) are presented. It was assumed that at low temperature gradients over the cross section of a wet body, thermal transfer of matter can be neglected, and phase transformations are absent (Posnov's criterion is equal to zero). By processing the experimental data on convective heat treatment of materials carried out by the least squares method, experimental equations for calculating the kinetics of drying have been obtained. Equations are given for determining the duration of drying, material temperature, heat flux density. On the basis of the theory of regular thermal regime, equations for the rate of heating of a solid and the rate of decrease in moisture content have been obtained. The verification of the reliability of the obtained equations and comparison of the calculated values of the parameters with the experimental ones are presented. An experimental dependence of the relative drying rate on the dimensionless moisture content has been established. The dependence of the generalized drying time on the relative moisture content is given. Also, based on the analysis of the experimental data on the thermal conductivity coefficients for wet thermal insulation materials, the dependences of the thermal conductivity coefficients on moisture content and temperature have been established. As a result of solving the criterion heat transfer equation, the values of the heat transfer coefficients for the period of the decreasing drying rate are obtained. The values of the Biot criterion in the processes of drying porous ceramics and asbestos are determined, too. It has been determined that the ratio of the moisture content loss rate to the drying rate in the first period does not depend on the drying mode and is a function of the initial moisture content.

A number of industrial plants that manufacture modern products use industrial furnaces in their technology. During their operation, it is necessary to comply not only with the current 

legislation, but also with the norms of consumption of fuel and energy resources. The growth of tariffs for energy resources has led to a significant increase in the energy component of costs price in the structure of the cost of production. As a result, even a small (several percent) change in the cost price can bring any industrial enterprise, including the most modern ones that use gas processing equipment, into the category of unprofitable. Having referred to technical regulatory legal acts, the present article proposes an energy efficiency indicator that allows monitoring energy efficiency at existing industrial plants with industrial furnaces. The world experience of operating glass industry furnaces is considered, existing approaches to determining the energy efficiency of this technology are presented. Based on the analysis of daily indicators of the operating modes of the technological line, methods have been proposed for estimating the rate of reduction in energy efficiency of a flat glass production line and forecasting the total and specific consumption of fuel and energy resources of industrial furnaces (in terms of a continuous glass furnace). The presented methods and the numerical calculations obtained for reducing the energy efficiency of a glass furnace make it possible to predict fuel consumption and form a correct annual application for its required volume to a gas supply organization, as well as evaluate the energy efficiency of production operating an industrial furnace and calculate the energy consumption rate for the output of a unit of production. Ultimately, more accurate determining of the cost of production of a particular industrial enterprise is achieved.

The substantiation of the choice of design parameters characterizing the mutual orientation of the mixed flows and the ratio of the geometric dimensions of the elements of the flow path of the jet pump that provide an increase in the energy characteristics of borehole ejection systems is given. Depending on the mutual orientation of the mixed flows, three variants of the design of the jet pump are possible, viz. the one with a parallel orientation of the working and ejected flows, the one with the inlet of the ejected flow at a sharp angle, and the one with a perpendicular orientation of the working and ejected flows. The magnitude of the angle between the velocity vectors of the mixed flows directly affects the intensity of vortex formation in the mixing chamber, the amount of energy loss and the efficiency of the jet pump; however, the simplicity of their manufacture remains the determining condition for choosing the design variant of the elements of ejection systems. Based on the use of the laws of conservation of energy, the 

amount of motion and continuity of the flow, it is determined that the level of energy loss during mixing flows is directly proportional to the magnitude of the angle of entry of the ejected medium. In the course of computer simulation of the jet pump workflow, an asymmetric distribution of hydrodynamic parameters for the non-parallel orientation of the mixed flows has been obtained. In order to reduce energy losses when mixing flows, the value of the angle of entry of the ejected flow must be taken in the range from 0 to 15°. In the case of the implementation of the zero head mode and the maximum ejection coefficient, minimal energy losses during mixing of flows are provided for the main geometric parameter of the jet pump equal to 2.375. In the course of experimental studies, the inverse dependence of the maximum value of the efficiency of a borehole jet pump on the value of its main geometric parameter represented as a power function, has been established. When using ejection systems that implement long-term technological processes (e. g., during oil production), it is necessary to take the minimum possible value of the main geometric parameter of the jet pump for the specified operating conditions.