Speed Control of Induction Motor Under Changing Load Torque Using PWM-PID Controller

Abstract

- Three-phase induction motor is widely applied in many applications requiring speed control precision such as milling machines and robotic systems and therefore, maintaining constant speed at a predefined value is essential. Several methods of speed control having been applied to three-phase induction in literature. This paper designs Pulse Width Modulation-discrete time Proportional Integral and Derivative (PWM-PID) controller to maintain a predetermined speed for three-phase induction motor in under constant and changing load condition. The mathematical model of the three-phase induction is presented and simulated in MATLAB/Simulink environment. Simulation results revealed that the motor exhibited excellent starting characteristics at no load, with minimal overshoot of 0.9036%and a relatively fast settling time of 0.2295 s. Under constant load of 50 N-m and changing load of 20 N-m and 50 N-m, the motor speed was characterised by settling time, peak time, and overshoot of (5.1107 s and 6.5983 s), (0.3 sand 0.3445 s), and (0.9394% and 1.003%), respectively. When compared with PI, the developed PID offered better performance in all transient response characteristics considered including improved stability.