Speed Control of Single Phase Induction Motor Using AC Chopper by Asymmetrical PWM Method

Abstract

ABSTRACT:In home appliances and in small scale industries, single phase induction motors are commonly used. Recently remarkable efforts have been made in adjustable speed -single phase induction motor drives (SPIMD's). Different types of PWM strategies have been used in speed control of SPIMD's, most widely sinusoidal PWM & space vector PWM strategies. Various converters technologies are taking a place in SPIMD's because of its low cost. The proposed project describes the several PWM strategies with an AC chopper to control the speed of single phase induction motor. Asymmetrical PWM technique has been used to operate the power electronics switches (IGBT) of an AC chopper. The main objective of this project is to maintain the speed of the single phase induction motor constant at different load conditions by using Asymmetrical PWM technique, which reduces the harmonic contents in motor current and increasing the motor efficiency. The simulation is carried out in MATLAB/SIMULINK with a Split Phase Induction Motor, where the motor is operated in normal PWM strategy, Hysteresis PWM strategy. The hardware is designed for the Asymmetrical PWM technique and results have been discussed. KEYWORDS: AC Chopper, Speed control, Asymmetrical PWM and THD. I.INTRODUCTIONA large number of motors are being used for general purposes in our surroundings from house-hold equipments to machine tools in industrial applications. The electric motor is now a necessary and indispensable source of power in many industries. The function and the applications of these motors are wide-ranging. For the many applications, the speed control of the motor plays a major role, which can be done using a wide range of control strategies.The purpose of a motor speed controller is to take a signal representing the demanded speed, and to drive a motor at that speed. The controller may or may not actually measure the speed of the motor. If it does, it is called a Feedback Speed Controller or Closed Loop Speed Controller, if not it is called an Open Loop Speed Controller. Feedback speed control is better, but more complicated, and may not be required for a simple design.Generally speed control of the motor can be achieved by varying the input parameters of the motor such as current, voltage etc. This can be achieved by various methods such as field control method, armature control method, WardLeonard method etc for DC motors and AC motors. Now a day, by the improvement of the power electronics devices, the flow of power to the motor is controlled by the switching action of the power switches (MOSFET, IGBT, IGCT etc). The nature of the speed control requirement for an industrial drive depends upon its type. Some drives may require continuous variation of speed throughout the operation, which ranges from zero to full speed, or a over a portion of the range. For most of the drives, however a control of speed within the range of ±10% of rated speed may be suitable.The existing methods for the speed control of induction motor are voltage control, frequency control...