Digital Phase-Locked Loop for Induction Motor Speed Control

The study of the speed control of induction motor drive using digital phase-locked loop is discussed. The block diagram and the control circuitry have been outlined. A mathematical model has been developed to predict the system performance. Different types of filters have been considered as part of the feedback control system, and their effects on the overall system behavior have been qualitatively studied. The system is tested using a 5-hp induction motor and an integrating type filter. Excellent speed regulation in the order of 0.002 percent has been obtained.