Mathematical modeling power-saving thyristor-motor drives of switching design

DC electric drives of rolling mills are the greatest electromechanical power consumers at iron and steel works. Energy indexes of these drives are far from the optimal ones. Most power losses are associated with consumption of reactive power caused by voltage phase control. Previous papers described the two-region control design based on rearranging reserve of the rectified EDV of the thyristor converter in steady-state and dynamic modes. Methods and systems of dependent control of excitation flow implementing that concept were proposed. A mathematical model of an electric drive of the wide-strip hot-rolling mill is required to study dynamic properties of this system. This paper depicts structures of control system models with coordinate switching controlled with the excitation circuit. Transient processes of the electric drive were investigated for a rolling cycle at different setting of EDV control circuits. Operational integrity and efficiency of the developed two-region speed control with switching units were proven. The results provide a rationale for introduction of the developed systems into the thyristor electric drives of rolling mills.