Speed Control of Single-Phase Induction Motor using Fuzzy Logic Technique with Magnetostrictive Amorphous Wire Speed Sensor

Abstract

Speed control of Induction Motors has been widely carried out with the aim of saving on energy, cost reduction and performance improvement of the motors and various methods have been used. Scalar control method which involves magnitude variation of the control variable is easy to implement. Its performance is however sluggish due to coupling e ect of torque and ux which are functions of current and frequency. A big drop in torque also occurs at lower speeds due to higher drop in the stator impedance. Vector control method which involves magnitude and phase variation of the control variable improves on the dynamic performance of the motors. To implement this method, rotor speed has to be measured and a speed sensor is therefore required. Introduction of the speed sensor increases the cost, size and complexity of the motor drive system. A sensorless vector control system has also been developed where the rotor speed is estimated rather than measured. This method requires the model equations of the motor which, for the Single Phase Induction motor (SPIM), are complex due to unequal resistance and inductance in the main and auxiliary windings. The estimation process also introduces errors in the system and this has an e ect on the overall e ciency of the system. This work presents a practical approach which aims at addressing the problems encountered in the already existing methods. The method involves the design and implementation of a Fuzzy Logic speed controller for the SPIM with magnetostrictive amorphous wire as the speed sensor. The sensor is in form xvi of a thin magnetostrictive amorphous wire in a pick-up coil and therefore it is expected that the issues of motor drive cost, size and complexity will be addressed. The performance of the sensor is tested and compared to the conventional digital tachometer. Fuzzy logic control technique is employed due to its ability to handle non-linearities, its independence on the plant's model and fast response. The controller is tested for di erent speeds of the SPIM at no load condition. The volts per hertz with feedback scalar control is employed in this work due to its ease of implementation.