Research On The Automatic Control System For Submerged Arc Furnace Electrode Lifting Based On The Large Current Detection

Submerged arc furnace heats the burden through the arc heat and resistance heat generated by the three-phase electrode in the furnace to make the burden generate redox reaction and then smelt ferroalloy. At present, in the most of domestic metallurgical plants, the primary side current by manual adjustment is used to control the three-phase electrodes lifting. This method cannot effectively realize the power balance of the three-phase molten pool. However, using the constant impedance control strategy of taking in view of the large current on secondary side of the transformer as the control parameter can better realize the power balance of the three-phase molten pool. But the secondary side current reaches several tens of thousands of ampere. It is quite difficult to detect. The error of using ratio of traditional transformer to calculate secondary side current is very large. For these problems, the Rogowski Coil is used to detect the secondary current in this thesis, the key contents are shown below:(1) The domestic and foreign situation of submerged arc furnace electrode lifting and large current detection are reviewed. It studies the production equipment and technological process of submerged arc furnace, and lays a foundation for the design of electrode lifting automatic control system.(2) Aiming at the problem that the secondary current of the submerged arc furnace transformer is difficult to be detected, this paper designs Rogowski Coil detection system and studies the method of detecting the secondary current by Rogowski Coil. After integration and amplification of the voltage signal outputted by Rogowski Coil use Fast Fourier Transform to decompose each harmonic wave, and sum for each harmonic wave to complete the detection of the secondary current of the submerged arc furnace transformer. Through MATLAB simulation and field test, the feasibility and effectiveness of the method are proved.(3) According to the production process of submerged arc furnace, the overall plan and hardware and software of automatic control system for submerged arc furnace electrode lifting are designed which use transformer secondary side current. The upper and lower structure of combining industrial control computer and Siemens S7-200 PLC is chosen in the hardware part. Visual Basic 6.0 is used as the development platform with Access data base to write software program of automatic control system in the software part. The constant impedance control strategy of electrode lifting is realized.(4) The whole control system is debugged and tested in the field, the data acquisition and automatic control of the electrode are accomplished. The debugging results reach the requirements of the control system.Realization of automatic control system for submerged arc furnace electrode lifting based on the large current detection has important significance for the smelting enterprises to reduce the energy consumption and labor intensity, and improve the automation level of the submerged arc furnace.