Applied Mechanics and Materials Vol. 792

Abstract: The article is devoted to the problems of management, managerial staff performance, and the production system organized nature in electrical engineering. Managers often appear to perform the work of low-skilled employees, which results in significant losses. The study presents the options to account and minimize the losses. Moreover, the proposed method is time and cost efficient and could be easily disseminated in electric machine industry.

Abstract: The paper is aimed to determine runoff limits of the Vakhsh cascade hydropower plant, which are the main parameters when setting optimum modes of the hydropower plant. It is proposed to increase power generation of the hydropower plant of the Vakhsh cascade by assigning the optimal modes of operation of hydropower plants. The peculiarities of managing the cascades of hydropower plants are described. The description of the Vakhsh cascade hydropower plant and the method of controlling the reservoir of the cascade of the hydropower plants are given.

Abstract: In the article the combined influence of surface effect, proximity effect, ring effect and slot effect on active and self-inductive resistances of the inductor, placed inside the hollow cylindrical workpiece, are investigated. It had been shown that the combined influence of these effects forms a distribution of current over cross-section of the inductor tube. That current determines the values of active and self-inductive resistances of the inductor. There had been presented dependencies of relative coefficients of active and self-inductive resistances of the inductor and relative geometrical parameters of the system "inductor – hollow finite-sized workpiece", the gap between the inductor and the workpiece, and specific resistance of heated nonmagnetic workpiece in presence and absence of internal magnetic core.

Abstract: The article presents results of studies of electromagnetic modes of side stirrer composed of multi-melting unit, based on the induction crucible furnace. Using induction crucible furnaces as highly efficient smelting unit in combination with an electromagnetic stirrer and heat control means electrodynamic effect on the molten metal at all stages of melting. The aim of this approach is to reduce the time of melting and improve the quality characteristics of the metal. This article describes the design of basic units, calculation of energy parameters and the study of stirrer modes when powered by a frequency converter.

Abstract: One of the most widespread methods of heating is induction mass heating because it offers certain advantages over similar technologies, including convectional and electrical heating. A significant economical effect can be achieved through optimization of heating modes and design parameters of induction heaters on the basis of modern optimal control theory for distributed parameters systems. The paper is devoted to the numerical simulation and optimal with respect to typical quality criteria control of thermal modes for metals induction heating before hot forming operations. Two-dimensional non-linear time-optimal control problem, problem of maximum heating accuracy and problem of minimum energy consumption are formulated and reduced to the mathematical programming problems. Optimization procedures are based on the developed at SamSTU alternance method of optimal control theory for distributed parameters systems. 2D FLUX code provides FEM analysis of interrelated electromagnetic and temperature fields during induction heating of a cylindrical billet before its hot forming. The model integrated into optimization procedures provides options for variation of the heating system parameters or billet geometry, and for evaluating the process optimization abilities. Computational results for optimal heating of aluminum cylindrical billets are shown and analyzed.

Abstract: The present article describes the analysis of electromagnetic field carried out by an analytical method in the system inductor–bath with melt (liquid metal) taking into account different winding characteristics of the inductor. It also defines integral and differential characteristics of the system for the most widespread windings of an MHD-stirrer.

Abstract: This paper presents a review of the research activities carried out at the Laboratory for Electroheat of Padova University (LEP) in the field of high efficiency through heating of aluminum workpieces. Induction heating obtained by rotating a billet in a DC magnetic field produced by superconductive coils was the first attempt to reach high electrical efficiency in mass heating of high conductive metals, like aluminum, copper and brass. More recently, the same concept has been applied by rotating rare earth permanent magnets around a metal billet kept in a fixed position. This technology appears much more promising because of lower cost of installation and a more robust mechanical design.

Abstract: The effect of a moving arc spot on a material of a plasmatron electrode is considered in the present paper. Temperature-dependence of material thermophysical properties is taken into account. Dynamics of temperature and thermal stresses fields are calculated. The characteristic feature of temperatures distribution along radius of an electrode is large gradient of temperatures in a narrow zone near to a surface which can cause large thermostresses and microcracks.

Abstract: The article deals with the description of an improved automatic control system for steel-making furnaces (electric arc furnaces and ladle furnaces) electrode positioning and the results of its production testing. The control performance of electrode positioning of the developed automatic control system was studied using a mathematical model, which included the main components of the system: the hydraulic drive of electrode positioning with a servo valve, electric circuit of the furnace described by Cassie nonlinear differential equation, impedance nonlinear controller. It was proved that a more accurate positioning makes it possible to significantly reduce electric power consumption per tap-to-tap cycle.

Abstract: Electric currents of the order 100 kA flow in secondary current leads of powerful electrotechnological installations. It causes active power losses and electromagnetic field power dissipation. To improve engineering-and-economical performance it is necessary to minimize pure resistance and inductance of current lead and symmetrize the parameters over phases while designing the installation. The paper considers approaches to formulate modern method for calculation pure resistance and inductance of secondary current leads in powerful electrotechnological installations.Interleaved conductors' packages have been examined as the longest partition of secondary current leads in ore-thermal furnace. The examination was carried out with numerical simulation of electromagnetic field of groups of interleaved water-cooled tubular buses (bus-packages) in ANSYS software. Dependencies of bus-packages pure resistance and inductance and their geometric parameters and interleaving ways for magnetic flux compensation have been obtained. Analysis of obtained results allows defining empiric formulae for calculation of electrical parameters of interleaved packages in powerful electrotechnological installations.