Abstract
The power circuit of the connection of the transformer windings of a 180 t electric arc furnace (EAF-180) of OJSC "Magnitogorsk Iron and Steel Works" (OJSC "MMK") is considered. It is shown that the main transformer is a three-winding machine capable of regulating the voltage under load in the tertiary winding. The brief characteristic of the control system of the electro-technological regime ArCOS is given. The system acts on the hydraulic system to adjust the position of the electrodes and switch the stages of the voltage-controlled load-transfer devices (OLTP) of the transformer and the reactor. It is shown that the deterioration in the quality of control and the decrease in the reliability of the chipboard are associated with the low system speed. Oscillograms of the arc current are shown when switching the voltage stages of the transformer confirming the presence of long pauses with each switching. This leads to loss of control over the melting mode. The second drawback of the ArCOS system is low speed associated with the inertia of the hydraulic system of electrode movement. Oscillograms of transient processes are presented with different adjustment of the impedance controller, which confirmed this conclusion. As a promising direction, the development of power circuits for furnace transformers with non-contact voltage regulation was noted. The proposed power circuit of the transformer with thyristor voltage regulation in the tertiary winding is realized implementing the well-known concept of voltage control with high dynamics. The results of the studies performed by the method of mathematical modeling are presented, which confirmed the feasibility of smooth regulation of voltage in the given range. The possibility of the proposed scheme for regulating the basic mode coordinates is determined at the established ratios of voltages and powers of the main and booster transformers. Directions for further improving the speed of the electrical control system are offered.
Keywords
Electric arc furnace, furnace transformer, power circuit, voltage regulation device, hydraulic electrode moving system, control, response speed, research, contactless regulation, thyristor voltage regulator, development, recommendations.
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