Digital Equivalent Load Monitor for Rolling Mill Motors

The reversing stands of plate rolling mills are made with individual (direct) roll electric drives to ensure the independent adjustment of their speeds. Launching new rolling profiles and optimizing rolling mill programs require improved calculation methods for the equivalent motor currents and torques. The available methods are based on the processing of smoothed load diagrams per one rolling cycle that are deemed the same for the main electric drive motors of the upper and lower rolls (UMD and LMD). This does not account for the differences in actual loads that may be 2–3 times different under the steady rolling modes. These differences lead to overloads, increased wear of electromechanical systems, and reduced motor efficiency. To avoid these drawbacks, the authors justified a calculation algorithm for the equivalent loads of motors using the parameters measured directly during rolling. The algorithm was tested on a 5000 plate rolling mill adjusted using the previously developed virtual control system commissioning procedure using digital twins. The authors present the results of the processing of UMD and LMD motor current and torque arrays obtained during the rolling of a five-piece batch. Some conclusions were made about the reliability of the results obtained and the efficiency of the practical application of the developed load monitor. The authors demonstrated that the equivalent LMD torque and current have smaller changes than the same figures for the UMD. This can facilitate the optimization of rolling programs and the improvement of the load division regulator algorithm.