Design And Construction Of Thyristor Based A/C Motor Speed Controller

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1     BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• AIM OF THE PROJECT
• OBJECTIVE OF THE PROJECT
• SCOPE OF THE PROJECT
• MOTIVATION OF THE PROJECT
• LIMITATION OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION OF THE PROJECT
• RESEARCH METHODOLOGY
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

• INTRODUCTION
• REVIEW OF RELATED STUDIES
• CONTROL APPROACHES OF INDUCTION MOTOR
• REVIEW OF VARIOUS METHODS OF CONTROLLING THE SPEED OF INDUCTION MOTOR

CHAPTER THREE

METHODOLOGY

• BLOCK DIAGRAM OF THE SYSTEM
• SYSTEM CIRCUIT
• CIRCUIT DESCRIPTION
• SYSTEM APPLICATION
• DESCRIPTION OF MAJOR COMPONENTS USED

CHAPTER FOUR

TESTING AND RESULTS

• CONSTRUCTION PROCEDURE AND TESTING
• INSTALLATION OF THE COMPLET DESIGN
• ASSEMBLING OF SECTIONS
• TESTING

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                             BACKGROUND OF THE STUDY

Electric AC motor works at fixed speeds and are ideally suited to applications where a constant output speed is required. However around half of all motor applications have some kind of varying speed demand and this includes processes such as moving air and liquids (fans and pumps), winding reels and precision tools.

Induction motor drives are employed in different industrial areas with a wide power range starting from few 100W to several MW. In modern industrialized countries, more than half the total electrical energy used is converted to mechanical energy through AC induction motors. Induction motors are extensively used in industrial and household appliances and consume more than 50% of the total generated electrical energy. Single-phase induction motors are widely used in home appliances and industrial control. During the last few years, the concept of speed and torque control of asynchronous motor drives has gained significant popularity. This way, it has been possible to combine the induction-motor structural robustness with the control simplicity and efficiency of a direct current motor. This evolution resulted to the replacement of the dc machines by induction motors in many applications in the last few years. Earlier only dc motors were employed for drives requiring variable speeds due to facilitate of their speed control methods [J. Zubek, 2010]. The conventional methods of speed control of an induction motor were either too extravagant or too inefficient thus limiting their application to only constant speed drives. They are used to drive pumps, fans, compressors, mixers, agitators, mills, conveyors, crushers, machine tools, cranes, etc. This type of electric motor is so popular due to its simplicity, reliability, less maintenance and low cost.    Today, with advancements in power electronics, microcontrollers, and digital signal processors (DSPs), electric drive systems have improved drastically. Initially the principle of speed control was based on steady state consideration of the induction motor. V/f control was the commonly used one for the open-loop speed control of drives with low dynamic requirements.

There are different methods of controlling induction motor for industrial application. However, the main aim of this work is to carry out a research on the voltage frequency ratio method of induction speed control technique. This method offers an easy way to regulate both the frequency and magnitude of the voltage applied to a motor. As a result higher efficiency and performance can be achieved by these motor drives with less noise. The most common principle of this is the constant V/Hz principle which requires that frequency and the magnitude of the voltage applied to the stator of a motor maintain a constant ratio. So by this,   the magnetic field in the stator is kept almost constant for all operating points. Thus, constant torque is maintained. Also allows the motor to achieve faster dynamic response (F. Blaschke, 2010).

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.

1.2                                                     PROBLEM STATEMENT

Conventional methods for starting and speed control of single-phase induction motor need often quite expensive external electrical equipment. Moreover, they require mechanical switches, which are the most troublesome parts. These switches suffer from mechanical wear, which affects the motor performance. Electronic methods based on using a thyristor in series with the stator main winding have been suggested to control the speed of the motor in order to solve the stated problem.

1.3                                                   AIM OF THE PROJECT

The main aim of this work is to use an electronic method to control the speed of an electric motor by varying motor input frequency and voltage using thyristor.

1.4                                             OBJECTIVE OF THE PROJECT

The objectives of this work are:

1. To provides variable speed to an electric motor
2. To accurately stop, or brake the motor

• To improve efficiency.

1.5                                              PURPOSE OF THE PROJECT

The purpose of the work is to convert the incoming electrical supply of fixed frequency and voltage into a variable frequency and variable voltage that is output to the motor with a corresponding change in the motor speed and torque.

1.6                                                 SCOPE OF THE PROJECT

The only really satisfactory way of obtaining the variable-voltage electric supply needed for speed control of an industrial electric motor was to generate it with a thyristor which is a power control device. Low power control circuits are used to monitor the principal variables of interest (usually motor current and speed), and to generate appropriate firing pulses so that the motor maintains constant speed despite variations in the load.

1.7                                                      MOTIVATION OF THE STUDY

Controlling the speed of an induction motor is necessary for both industrial and local applications in that it gives adjustable Speed Drives include energy savings, efficient motor starting, reversing, and speed and position control. The advantages of using this method of motor speed control is because it is cheap and efficient means of controlling the speed of an induction motor. However, advantages discussed above were points that motivate the carrying out of this research work.

1.8                                                        LIMITATION OF THE STUDY

As we all know that no human effort to achieve a set of goals goes without difficulties, certain constraints were encountered in the course of carrying out this project and they are as follows:-

1. Difficulty in information collection: I found it too difficult in laying hands of useful information regarding this work and this course me to visit different libraries and internet for solution.

Difficulty in parts gathering: I found it too difficult when gathering electronics parts used for the prototype because some of the parts are not sold in our local market.

1.9                                                      SIGNIFICANCE OF THE STUDY

This research work will throw more light on the techniques for controlling the speed of electric motor. This study will also be designed to be of immense benefit to all the users of electric motor most especially in industries.

It will also serve as a guide to whoever that wants to purchase speed controller for induction motor.

Finally, it will also serve as a useful piece of information for both producers and users of electric motor speed controller.

1.10                                           RESEARCH METHODOLOGY

In the course of carrying this study, numerous sources were used which most of them are by visiting libraries, consulting journal and news papers and online research which Google was the major source that was used.

1.11                                     PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.