Browsing by Author "Kolychev, Sergei V."

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Investigation of Electromagnetic Parameters and Electromechanical Characteristics of a DC Machine Based on the Finite Element Method
(Видавничий дім «Гельветика», 2024) Kachura, Oleksii V.; Nikolenko, Anatolii V.; Kovalenko, Viktor; Kuznetsov, Vitaliy V.; Syanov, Alexander; Tsyplenkov, Dmytro; Kolychev, Sergei V.; Gurin, Yevgen
ENG: The verification calculation of the serial machine of direct current (DCM) MUN-2 with a modified excitation system based on the finite element method (FEM), which allows to investigate the characteristics and electromagnetic parameters of DCM taking into account new design solutions in static, quasi-static and dynamic modes of operation. The finite element model of the DCM can be combined with the chain model of the power supply based on the joint solution of the field and circuit equations, which makes it possible to investigate the characteristics of the engine in various modes when the anchor winding supplies signals of any shape. Based on the obtained results, the verification calculation of the DCM MUN-2 with a modified excitation system based on MSE allows the study of the characteristics and electromagnetic parameters of the DCM, considering new constructive solutions in dynamic modes of operation. The resulting DCM field model can be combined with the power source circuit model based on the joint solution of the field and circuit equations, which makes it possible to study the characteristics of the motor in different modes when feeding the armature winding with signals of any shape. The work established that the motor reaches the maximum rotation speed after 300 ms at a voltage of 120 V on the armature winding. At the same time, there is a surge in the starting current of the armature up to 2.0 A with subsequent stabilization at the level of 0.08 A. The starting torque reaches 1.2 Nm. The MUN-2 reaches the nominal rotation frequency at the nominal load, accompanied by an increase in the armature winding current to 0.7 A. During the operation of the motor, an electromotive force is induced in the armature winding, which, when the motor reaches the nominal rotation speed, stabilizes at the level of 20 V and has a peak character. Maxwell’s system of electromagnetic fields and analytical and mathematical methods for partial differential equations are used to solve the problems. The finite element method is used to solve the differential equations of the magnetic field.
Mathematical Model of a Semiconductor Structure Based on Vanadium Dioxide for the Mode of a Conductive Phase
(MDPI, Basel, Switzerland, 2025) Kachura, Oleksii V.; Kuznetsov, Valeriy; Tryputen, Mykola; Kuznetsov, Vitalii V.; Kolychev, Sergei V.; Rojek, Artur; Hubskyi, Petro V.
ENG: This study presents a comprehensive mathematical model of a semiconductor structure based on vanadium dioxide (VO2), specifically in its conductive phase. The model was developed using the finite element method (FEM), enabling detailed simulation of the formation of a conductive channel under the influence of low-frequency alternating voltage (50 Hz). The VO2 structure under investigation exhibits pronounced electric field concentration at the surface, where the field strength reaches approximately 5 × 104 V/m, while maintaining a more uniform distribution of around 2 × 104 V/m within the bulk of the material. The simulation results were validated experimentally using a test circuit. Minor deviations—no greater than 8%—were observed between the simulated and measured current values, attributed to magnetic core saturation and modeling assumptions. A distinctive feature of the model is its ability to incorporate the nonlinear dependencies of VO2’s electrical properties on frequency. Analytical expressions were derived for the magnetic permeability and resistivity of VO2, demonstrating excellent agreement with experimental data. The coefficients of determination (R2) for the frequency dependence of magnetic permeability and resistance were found to be 0.9976 and 0.9999, respectively. The current version of the model focuses exclusively on the conductive phase and does not include the thermally induced metal–insulator phase transition characteristic of VO2. The study confirms that VO2-based structures exhibit high responsiveness and nonlinear switching behavior, making them suitable for applications in electronic surge protection, current limiting, and switching elements. The developed model provides a reliable and physically grounded tool for the design and optimization components based on VO2 in power electronics and protective circuitry.