Modeling of the thyristor controlled rectifiers for control of Ward - Leonard system

Abstract

The classical scheme of DC motor control developed by Ward Leonard, employs for this purpose a rotating DC generator, the armature voltage of which is controlled through the field. The DC generator is driven by an AC motor and running at approximately constant speed. The disadvantages of this type are in the number of full-size machines in the chain, which raises the cost and lowers the overall efficiency. Combined with up-to-date control, drives of this type are still in use today. This paper presents a study of the model of the thyristor controlled rectifiers for control of Ward – Leonard system. The control structure consist outer speed regulation loops operating through a faster two current regulation inner loop. One for the motor armature current and two for DC generator field current. This paper also describes the mathematical models of the generator, motor, mechanical load, rectifiers, speed regulator, current regulator and completed control system implemented in SIMULINK. At the end, simulation results are included to illustrate the effectiveness of the proposed controlled method.