Design and Construction of Automatic Change-Over for Three Phases

ABSTRACT

         The main aim of any electric power supply in the world is to provide uninterrupted power supply at all times to all its consumers. Although in developing countries, the electric power generated to meet the demands of the growing consumers of electricity is insufficient hence instability and outage. Power instability or outage in general does not promote development in the public and private sector. The inventors do not feel secure to come into a country with constant or frequent power failure. These limit the development of industries. In addition, there are processes that cannot be interrupted because of their importance. For instance, surgery operation in hospitals, transfer of money between bank and lots more. Power instability and outage in developing countries (Nigeria) creates a need for alternative source of power to backup the main supply. Automatic changeover switches find a wide application scope wherever the reliability of electric supply from the utilities is low and it is used in lighting motor circuits wherever continuity of supply is necessary. For switching to an alternative source from main supply and vice versa.

         This project is a design of an automatic changeover switch this means that when there is any mains failure, the automatic changeover switch will change to an alternative power supply (GENERATOR) and back to the main supply when it is restored.

         The purpose of this project is to maintain constant supply to the main circuit that is being supplied by making up for the time delay that usually accompanies the manual switching from one source to another.

         The design comprises of the power connection circuit and control connection circuit. The main components to be used include contactor, relay, timers, rectifier e.t.c.

TABLE OF CONTENTS

 Title Page                                                                               i

Certification                                                                             ii

Acknowledgements                                                                  iii

Abstract                                                                                  iv

Table of Contents                                                                    v

CHAPTER ONE

1.1    Introduction                                                                    1

1.2    Aim and Objective of the Project                                      3

1.3    Scope of the Project                                                        3

CHAPTER TWO

2.1    Literature Review                                                             5

2.2    Manual Change-over Switch                                             5

2.3    Automatic Change-over Switch                                         6

2.4    Related Work                                                                  10

2.5    Reasons for Automatic Change-over Switch                      16

2.6    Problems of Automatic Change-over Switch                      17

CHAPTER THREE

3.1    Methodology (Material and Methods)                                18

3.2    Circuit Conductor                                                            18

3.3    Circuit Breaker                                                                19

3.4    Reset Timer                                                                    20

3.5    Contactor                                                                       21

3.6    Operation of Timer Delay                                                 24

3.7    Principle of Operation                                                      25

CHAPTER FOUR

4.0    Construction                                                                   29

4.1    List of Component Used                                                   29

4.2    Vero Board                                                                     29

4.3    Bread Board                                                                    30

4.4    Soldering Iron                                                                 33

4.5.1 Testing, Maintenance and Discussion                                36

4.5.2 Polarity Test                                                                    36

4.5.3 Insulation Resistance Test between the Live and Neutral Conductors                                                                     37

4.5.4 Earthling Test                                                                 37

4.6    Maintenance of Contactor and Installation                        37        

CHAPTER FIVE

5.1    Conclusion                                                                      39

5.2    Recommendation                                                            39

         References                                                                      40

         Bill of Engineering Measurement and Evaluation (BEME)    41