An improvement in operation of a crop cobble shear system for steel rolling mill using direct torque control induction motor drive

The paper describes how a Direct Torque Control (DTC) drive technology has been used to improve the operation of a Crop Cobble Shear (CCS) system in a steel rolling mill. The CCS equipment, with emphasis on the motor and drive system, is fully described and the issues with the original system are described. The existing system uses a DTC drive. However, during the cobble cutting mode, depending on the bar length, the original DTC drive experiences over-heating or overcurrent faults that cause production downtimes. A model of the overall system has been developed and introduced into a simulation model such that the Direct Torque Control may be analysed and modified to improve performance. Simulated DTC induction motor drive is compared with the existing platform from a steel plant. Experimental data from measurements on the system in the steel mill are favourably compared with simulation results. This comparison shows the system has been simulated to determine a suitable approach to improving the DTC. Following simulation, the modifications were made to the system and measurements carried out to verify the improvement.