Design And Construction Of Automatic Change-Over For Three Phases Using 555 Timer And Contractor

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, rectifiere.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

CHAPTER ONE

1.1   INTRODUCTION

Power instability in developing countries creates a need for automation of electrical power generation or alternative sources of power to back-up the utility supply. This automation is requiring as the rate of power outages become predominantly high. Research in the field of electrical electronics engineering has led to the tremendous discovers and inventions especially in the area of automation and power control. These invention have been useful in solving the over-in.

Creating problem posed by power generation, distribution and control, which has been a cause of concern especially in the third world countries (developing countries) like Nigeria. Most industrial and commercial process is dependents on electric power and if process of a change-over is manual, serious time is not only wasted but it creates room for human error (in the area of change over connections) which could result in great economic loss.

This project is all about the construction of an automatic generator change-over panel with timer which aids in the switching over to alternation power supply authority i.e.Power Holding Company of Nigeria (PHCN) popularly known as NEPA which is the main power regulating body in Nigeria. This project consist of circuit breakers, electromagnetic contactor which carry heavy load current relay which work with the principle of electromagnetic induction  because it will receive electrical signal to trigger and neumatic timer all incorporated and interconnected to achieve the desire goal.

Also this project is constructed in such a way that provision is made for manually operation (it can be operated manually) when necessary for required for example, in the situation whereby voltage supplied by the authority (PHCN) is fluctuating and one may decided not to use it, so the constructed automatic change-over panel can be permanently switch to generator set temporarily pending the time that utility supply is stable moreover in the hospital where where surgery operations is needed to be carry out and power outage for even five second cause damages, one may decide to neglect the supply from authority (PHCN) and permanently switch the panel to manual operation pending the time or period by which surgery operation is completed. During the pending period this change-over will be working continuously in manual operation. Fill someone or the operation has to switch over to automatic operation. As said earlier, provision is made for these types of generation in this project and there is separate switch that performed the function.

1.2   AIM AND OBJECTIVE OF THE PROJECT

The aim of the project is to design and construction automatic change-over switch load from the mains power supply (PHCN) to a backup power supply (Generator) with simplicity.

The advantages of this project cannot be over emphasized, since outage is a major problem is the advent developing nations like Nigeria, for example, power failure of minute in an airport terminal can create losses that could run into millions of dollars due to loss in air traffic system control the ability for back-up to start and change-over automatically becomes imperative under such circumstances.

Also, this project could play a large role in the security in banks and companies i.e. an outage of up to ten minute in an organized setup is enough to do all the damage required with such an automatic change-over device in place the generator backup would no longer have to depend on security men and of course reduced fear of system breakdown in the companies there by ensuring smooth running of economics activities.

1.3   SCOPE OF THE PROJECT

Basically, this project is a three phase automatic change-over device with the power capacity of 50KVA. Generator as deducted from my calculations it shows that generator of power rating ranging from 0.5KVA to 50KVA is required to be use for this project though the contacts of electromagnetic contactor relays and circuit breakers. Also the maximum load current should be between the ratings of 10A to 90A load current. Therefore the use of 10Amperes in this project is because of future extension.