Design of controllersKrishan AroraAssistant ProfessorLovely Professional University

Need of Controller design The control system consists of an outer control loop for rotational speed and an inner control loop for current. The output of the speed controller is an input (current reference) to the current controller. The block diagram of the control system is shown in Fig. 2. The current and voltage limits are not included in Fig. 2 when these limits are active, they cause nonlinearity in the control system. The two controllers can usually be designed independently, since the mechanical dynamics of the system is usually much slower than the dynamics of the armature circuit.

Controllers and Controller Design

Speed Control Loop

Four-Quadrant Drive A four-quadrant drive allows the DC motor to be driven in both rotational directions both in the motoring mode and in the regenerative braking mode. For four-quadrant operation, the power electronics must allow the direction of the armature current to be changed2. Figure 5 illustrates the four-quadrant drive based on two antiparallel six-pulse thyristor bridges. It is assumed that only one of the bridges is operated at a time (i.e., no circulating-current operation).