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Publisher Copyright: © 2022 IEEE. At present, carbon fiber has become widespread and used in electromechanical technologies in the development of processing technologies. However, when modeling carbon fiber, difficulties arise-often, the mechanical parameters of separately carbon fiber and epoxy resin are known, and only for a specific layer thickness. Also, carbon fiber is used as a composite material, and, therefore, there is a need to determine the optimal sequence of sheet orientation for use in electrical machines. With the help of the COMSOL Multiphysics software package, the possibility of determining the homogenized properties of carbon fiber bonded with epoxy resin was investigated, and the issue of determining the optimal sequence of sheets from the point of view of minimizing mechanical stresses was also considered. The application of a carbon fiber sleeve for a high-speed synchronous reluctance electrical machine has been considered. The mechanical analysis results indicate this technology's applicability in the field of high-speed electromechanics.

Publisher Copyright: © 2021 IEEE. Currently, due to the growing use of renewable energy technologies and hydrogen energy technologies, highspeed electric machines are of particular interest. High-speed electric machines have proven themselves well in compressor units and can improve the overall efficiency of the entire unit by eliminating the gearbox. However, the design and operation of these electric machines are accompanied by several difficulties, such as the resulting increased centrifugal forces, leading to increased mechanical stresses in the structure of the rotor. In this paper, a high-speed synchronous reluctance motor is considered as the object under study. The aim is to investigate the possibility of reducing mechanical stresses in the rotor steel by optimizing its topology while maintaining the output electromagnetic power.

The article provides a literature review of existing methods for determining three-phase transformer magnetizing current, and describes the disadvantages of studied methods for today's technological processes. An approach to calculating three-phase power transformer magnetizing current and considering its asymmetry based on the energy parameters of electrical steel has been developed.

Relay systems, like most non-linear systems, are mainly calculated by approximate methods. However, in the class of relay systems, in some cases, calculation by the analytical method is possible. The study of the stability of the obtained self-oscillations must also be carried out analytically, for example, using the apparatus of discrete circuits and signals. This method is quite simple to implement and allows one to study stability in theoretically important cases, for example, if the degrees of the numerator and denominator differ by 1 order or coincide. In the case of the integrator and the discontinuous transient response of the linear part, it is necessary to clarify the general methodology for studying stability, since the transition to discrete circuits by the method of full correspondence of impulse characteristics is incorrect, and in the case under consideration, the transition is carried out by the method of full correspondence of transient characteristics.

The article analyzes existing methods for calculating no-load losses of a transformer. The disadvantages of approaches used today are noted and a method is given for calculating losses based on the geometry of transformer, as well as the type of steel used. Particular attention is paid to the issue of no-load current active component asymmetry of three-phase transformer.

The contact connections of current conductors under the influence of vibration change the harmonic composition of the currents flowing through such connections. There are presented formulas to calculation additional current harmonics produced by influence of contact connection vibration. Presented numerical estimates show the importance to account such influence under analysis the electrical currents’ harmonical compositioin flowing through such compounds.

The features of modeling DC machines in MATLAB Simulink are considered. It is shown that in this simulation environment there is no possibility of taking into account the nonlinear magnetization curve of the machine and the presence of residual magnetic flux. The possibility of modeling and obtaining the correct characteristics of DC machines in MATLAB Simulink by making changes to the library block of an additional function is considered. The analysis of the applied methods of approximation of nonlinear dependencies is given and their disadvantages are indicated. A method has been developed for specifying a non-linear magnetization curve of a direct current machine and finding its analytical dependence without carrying out their full electromagnetic calculation using only passport (catalog) data.

The cryopreservation eff ect on viability of black currant cuttings (Ribes nigrum L.), sweet cherry pollen (Cerasus avium L. Moench), Prunus rossica Erem. diploid plum and Prunus domestica L. garden plum pollen, as well as the seeds of wild medicinal plants: Syrian rue (Peganum harmala L.), tansy (Tanacetum ulutavicum Tzvel.) and sawwort (Serratula dissecta Ledeb.) was studied. The viability in 5 cultivars of R. nigrum L. was decreased after cryopreservation; in 7 cultivars of C. avium L. (17 cultivars totally) it was increased, in 6 cultivars there were no changes, in 4 ones it was decreased; in 3 varieties of P. rossica Erem. (9 cultivars totally) the one was increased, in 3 ones there were no changes, in 3 ones it decreased; in 6 cul-tivars of P. domestica L. (13 cultivars totally) this index was increased, in 3 ones there were no changes, in 4 ones it decreased; in P. harmala L. seeds it was unchanged; in the seeds of S. dissecta Ledeb. it was increased. For the seeds of three medicinal plants there were selected the optimal concentrations of cryoprotectants and thawing modes as follows: P. harmama L. – 100% glycerol, slow freeze-thawing; T. ulutavicum Tzvel. – 10% sucrose, slow warming; S. dissecta Ledeb. – 3% DMSO, rapid warming. Probl Cryobiol Cryomed 2019; 29(1): 044–057

Currently, the most used electric machines are three-phase induction motors. Due to its design, such motor is one of the most energy-efficient and reliable electric machines. However, due to the increase in operating costs of electric machines, the problem of the correct and optimal design of electromechanical equipment arises to reduce damage and depreciation from working in critical mode such as the short circuit that occurs every time the motor starts. Long emergency mode lead to exceeding the norm of the permissible temperature of the motor windings and to a decrease in its reliability. This article is devoted to mathematical modeling of short-circuit conditions of the induction motor’s short circuit mode with a squirrel-cage rotor.

Analysis of available solutions to the problem of determining an electrodynamic forces (EDF), acting in conductors with variable cross section in the region of narrowing when an electric current flows through them, shows that almost all of them are based on the model of current distribution in this area proposed by G. B. Dwight and based on insufficiently substantiated assumptions. The paper presents and substantiates mathematical model of currents distribution in specified area, different from the model of G. B. Dwight. General equations are given that are suitable for developing algorithms for numerical estimating of mentioned EDF distributions.

When a transformer works under the operating mode an emergency short circuit may occur. This is a dangerous emergency mode, in which the transformer currents are many times higher than their rated values. Such currents may lead to isolation overheating, reliability decreasing or even to transformer failing. In order to prevent damage during the critical mode and increase the transformer reliability by using a protector, it is necessary to determine the short circuit current value. The article considers the problem of optimal accurate design by the method of mathematical transformer modeling by determination of short circuit current value in emergency mode.

Relay systems, like most non-linear systems, are mainly calculated by approximate methods. However, in the class of relay systems, in some cases, calculation by the analytical method is possible. The study of the stability of the obtained self-oscillations must also be carried out analytically, for example, using the apparatus of discrete circuits and signals. This method is quite simple to implement and allows one to study stability in theoretically important cases, for example, if the degrees of the numerator and denominator differ by 1 order or coincide. In the case of the integrator and the discontinuous transient response of the linear part, it is necessary to clarify the general methodology for studying stability, since the transition to discrete circuits by the method of full correspondence of impulse characteristics is incorrect, and in the case under consideration, the transition is carried out by the method of full correspondence of transient characteristics.

In remote and inaccessible areas, the problem of saving fuel and other resources arises from the lack of the ability to build a full-fledged power station in these areas. To reduce energy costs, resort to the use of renewable energy sources and the construction of hybrid power plants. The article discusses the main issues of the operation of a hybrid power plant. Its structure was studied with the highlight of the main functional units. This power plant was simulated using software and output characteristics were obtained.

Nonlinear dependence of the transition contact connection as a result of switching device’s vibration causes spectrum of additional harmonics in switched circuit. Identified the influence of such non-sinusoidality on electrical devices containing such connections in their’s composition. This article is devoted to numerical evaluation of vibroactivity’s influence of contact joint on the voltage transformer’s parameters.

Due to nonlinear dependence of transitional electrical contact connection from the force which are compressing contact in system "Switching Electric Apparatus of alternating current - Switched device", harmonic composition of currents entering the switched device changes. Numerical estimates of such effect are presented.

The transport and magnetic properties of cation-substituted manganese sulphides CexMn1-ХS in the 4K - 450K temperature range in magnetic fields up to 90 kOe are studied. The hysteresis of curve magnetization for X=0.01 and nonlinear field behavior of the magnetization at X = 0.05, the sharp Curie temperature drop were found. The sharp maximum in the temperature dependence of resistivity was observed. The shift of the maximum temperature to low temperatures at cerium ion concentration increasing and in magnetic field was established. Model of orbital polaron for explanation of experimental datа was used.

Height stimulation and inhibition the flowering, formation of seeds and germination capacity is observed in the regions highly polluted with products of combustion and domestic cottage processing of oil. At the same time the level of chromosome aberration increase significantly in root meristema of seedlings of these plants