Analysis of Transient Firing Angle in Reversible Thyristor Drive Speed Regulator for Mill Motor

When designing a high-response thyristor-drive speed regulator with internal multicontrol loops for a rolling mill motor, the behavior of the transient firing angle must be taken into consideration to ensure consistent thyristor switching, which is often neglected, and to achieve the required dynamic performance. The critical conversion modes in which the minimum transient firing angles in rectification and inversion may appear in a dual thyristor converter for four-quadrant motor drives are clarified. Two methods of analyzing the transient firing angles in the critical conversion modes and the results of calculations of the minimum transient firing angles under specified operating conditions are also presented. The calculated results are verified in laboratory tests.