Digital Overheating Protection System for Rolling Mill Stand Motors

Developing overheating protection systems for high-power synchronous motors of rolling mills is a relevant research area. This problem has not gained proper interest in recent years. The existing R&D solutions address synchronous motors with permanent magnets and cannot be applied immediately to motors with electromagnetic excitation. Modern overheating protection systems must be developed together with digital temperature monitors. It is feasible to develop two-stage protection systems that alert the operators in the first stage and shut down the mill upon rolling completion in the second stage. To this end, the authors developed a temperature monitor based on a 4 -mass digital model created using the domains of the Simscape Thermal Models library. Using the stand motors of the 5000 plate mill, the authors developed the structure of a protection system that provides continuous control (recovery) of temperature based on the signals from the industrial programmable logic controller (PLC) that controls the electric drives. The algorithm explaining the operation of the protection system is reviewed. To assess the reliability of temperature recovery and protection triggering efficiency when the stator winding temperature exceeds the set threshold, a passive experiment was conducted, in which the motor overheated. The results confirm the feasibility of the developed adaptive two-stage protection algorithm, and the authors provide recommendations on its industrial deployment.