Abstract
When expanding the product range of plate rolling mills through the sheet production from hard-to-deform steel grades, challenges arise in verifying the thermal state of the stand motors and assessing the limitations imposed by the electric drive on the technological process. Based on a conducted literature review, it is shown that in the methods known from electric drive theory, the equivalent load calculation (torque and current equivalenting) is performed using simplified tachograms and load diagrams constructed for the heaviest pass, which is not always possible to determine. Furthermore, the difference in rolling forces and, consequently, in the main electric drive torques of the upper and lower rolls (UDR and LDR), characteristic of stands with individual roll drives, is not taken into account. The presented paper proves this by analyzing oscillograms obtained from the 5000 plate rolling mill. A characteristic of the previously developed method for equivalenting speeds and torques, based on processing data reconstructed using a coordinate observer, is given. In that method, the final assessment of the motor thermal state is carried out during rolling, which can lead to the violation of the motor thermal conditions, if reductions are set incorrectly. In this regard, the methodology for calculating equivalent parameters is substantiated and can be applied at the stage of virtual development of tachograms before their implementation at the mill. Load conditions are relatively simply calculated using empirical dependencies that take into account the static torque or current, as well as the duration and rates of acceleration and deceleration under load. A comparison was made of the equivalent torque obtained over 9 finishing rolling passes by processing experimental data with an observer (according to the previously developed method) and by calculating them using analytical dependencies. Satisfactory convergence of the results was confirmed. Recommendations for the implementation of the new methodology in existing rolling mills are given. Its advantage is high efficiency with minimal risks of motor overheating.
Keywords
individual electric drive, rolling mill stand, plate rolling mill, motor, load, equivalenting, methodology, empirical dependencies, results, analysis, recommendations
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