ABSTRACT

Induction motors have been considered for many industrial applications due to their low.
maintenance, low cost, high efficiency, simplicity of design, and robustness. Despite of its many advantages, the induction motor has encountered problems in its speed control. The speed control of three phase squirrel cage induction motors is difficult and complex process which affects its performance. To address this issue, conventional pulse width modulation (PWM) technique is commonly used to control its speed. However, conventional PWM technique has certain limitations of producing harmonics, uneven frequency spikes and cumbersome circuitries along with extra expense/cost. Hence, PWM technique due to these limitations is not suitable for speed control of induction motors.
Alternatively, PID controllers are applied for the speed control of induction motors. However, PID based speed control of induction motor also encountered the problem of parameter tuning. Incorrect tuning of PID controller causes unsatisfactory results in speed control of induction motor during transient conditions. Furthermore, the PID controllers are not suitable for complex and non-linear systems.
To address these issues, this research proposes fuzzy logic controller based speed control of three phase induction motor. The test system and proposed controller has been modeled in Matlab/Simulink environment. The response of the proposed technique has been analyzed for different load variations ranging from no load torque to full load torque. Furthermore, the response of proposed fuzzy based technique is compared with PWM, PID controller based techniques in order to show its effectiveness. The simulation results
have shown that proposed fuzzy logic controller provides efficient speed control of three phase squirrel cage induction motor for all cases as compared to conventional PWM technique PID technique.