Design And Construction Of An Automatic Changeover Switch With Contactor And Timer

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 power instability and outage.

Power instability or outage in general does not promote development in the public and private sector. The investors 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 banks and lots more. Power instability and outage in developing countries (Nigeria) creates a need for alternative sources of power to backup the mains supply.

Automatic changeover switches find a wide application scope wherever the reliability of electrical 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 lapse or 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; contactors, indicators and timer.

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRCT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• OBJECTIVE OF THE PROJECT
• PURPOSE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• LIMITATION OF THE PROJECT
• SCOPE OF THE PROJECT
• APPLICATION OF THE PROJECT
• DEFINITION OF TERMS

CHAPTER TWO

LITERATURE REVIEW

2.1     OVERVIEW OF RELEVANT TECHNOLOGY

2.2     REVIEW OF RELATED WORKS EXISTING SYSTEM

2.3     REVIEW OF ELECTRICAL PHASES

2.4     REVIEW OF THREE-PHASE ELECTRIC POWER

2.5     REVIEW OF THREE PHASE GENERATION AND DISTRIBUTION

2.6     REVIEW OF THREE-WIRE AND FOUR-WIRE CIRCUITS

2.7     HISTORICAL REVIEW OF POWER FAILURE AND SYSTEM RELIABILITY

2.8     TYPES OF POWER FAILURE

2.9       DESCRIPTION OF A CONTACTOR

CHAPTER THREE

3.0     METHODOLOGY

3.1     BLOCK DIAGRAM OF THE SYSTEM

3.2     BASIC OPERATION OF A CONTACTOR

3.3     CIRCUIT DIAGRAM

3.4     CIRCUIT DESCRIPTION

3.5     HOW TO WIRE A CONTACTOR

CHAPTER FOUR

4.0      RESULT ANALYSIS

4.1     CONSTRUCTION PROCEDURE AND TESTING

4.2     CASING AND PACKAGING

4.3     ASSEMBLING OF SECTIONS

4.4     TESTING OF SYSTEM OPERATIONOBSERVATIONS

4.6     PROBLEM ENCOUNTERED

CHAPTER FIVE

• SUMAMRY
• CONCLUSIONS/SUGGESTIONS

5.3     REFERENCES

CHAPTER ONE

1.0                                                      INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

In Nigeria today the problems of power outage across phases is so rampant thus leading to some sensitive equipment and appliances being redundant, this could sometimes be the cause of one phase going out with respect to the other.

It may surprise one to note that in an attempt to solve this problems, so many unskilled electricity consumers has  in recent past resorted to some crude means of swapping between phases to obtain power. So many souls have been lost in this act. This is an undesirable condition to consumers and the need now arises to design a device that can automatically select among the phases and make power supply available at the consumer’s terminal.

However, this can only be possible if one have a three phase met or and there is supply from any of the service line or the entire line, this project known as a three phase automatic phase selector has been constructed with a view of solving the problems stated above. The design and construction was based on the principle of Electro magneto-Dynamism and alignment as demonstrated in the contactor arrangement.

Among other components are the timers miniature-circuit breakers the contactors and indicator bulbs, the ease with which the device is operated is well elaborated to ensure simplicity effort were made to present a stop by step operation of the project. As much as there is no project without limitation and applications, we have as well dedicated a section of this paper to look into it.

In order to ease the effort of technicians in restoring the devices should there be any malfunction associated.

Faults and how they are cleared is presented, however, there are no user serviceable parts in the device therefore all maintenance should be referred to a qualified electrical personnel.  The main of the proposed work is to provide seasoned, tested, trusted and sustainable three phase automatic changeover switch using contactor and timer.

1.2                                   PROBLEM STATEMENT

The use of relay in building automatic changeover has many disadvantages and limitations such as: Relays are generally classified as carrying loads of 10A or less and the maximium voltage for the relay is 250vac. Relays on the other hand can and often are both Normally Open and/or Normally Closed depending on the desired function and also a relay can only be used for single phase power supply. This study was carried out to overcome such problem:  contactor would be used for loads greater than 10A, but this definition, while simple, gives an incomplete picture. It leaves out any physical differences, or standards. Contactors are almost exclusively designed to operate with normally open (Form A) contacts. Because contactors are typically carrying high loads, they often contain additional safety features like spring-loaded contacts to help ensure the circuit is broken when de-energized. This is important because in high load situations contacts can weld themselves together. This can create the dangerous situation of a circuit being energized when it is supposed to be off. Spring-loaded contacts help to reduce this chance, as well as ensure all circuits are broken at the same time. Since relays are typically for lower power, spring-loaded contacts are much less common, and lastly, contactor can handle Up to 1000VAC.

1.3                                          OBJECTIVE OF THE PROJECT

The objective of this work is to design a device that will overcome power interruption by changing from mains to generator and vice-versa. This device is capable of handling load up to 60A.

1.4                             PURPOSE OF THE PROJECT

The purpose of the project is to avoid or minimize the level of power interruption in our home, offices or industries.

1.5                                      SIGNIFICANCE OF THE PROJECT

Industries require three phases power to run their machinery. Some of them require continuous \ uninterrupted power to maintain their data.

Auto changeover introduces an automatic solution to overcome power interruption by transferring a power supply from its primary source automatically to a backup generator when it senses a failure or outage occurring in the primary source until utility power is restored

1.6                         LIMITATION OF THE PROJECT

In every home, office or industries, automatic changeover plays a vital role, that is, It provides a means of switching from one phase of AC mains to another in the case of failure in the existing source; This project has been improved on the existing types of electromechanical device that has being in use over the years.

In the course of designing this project, different kinds of problem was notice such as:

1. Because of the high current involved, thick wiring was used.
2. The cost of designing the device is higher the parts are higher than that of the manual changeover.

• Changeover switches have been known to respond to false signals when the switching device becomes faulty, this scenario that could waste generator power, albeit in small amounts.

1. Operating voltages: 220V-240
2. It can handle up to 60A.

1.7                                 SCOPE OF THE STUDY

This work covers only a three phase automatic changeover which can only be used for providing a means of switching from one phase of AC mains to another in the case of failure in the existing phase.

1.8                       APPLICATIONS OF THE PROJECT

This device provides constant power supply in our:

• Homes
• Workshops
• Worship centre (such as churches or mosque)
• Offices
• And any other places that electrical energy is been used

1.9                                   DEFINITION OF TERMS

CHANGEOVER: Generally, a changeover switch is a system which could be operated manually or automatically , that changes one source of power supply to another source in case of power failure from either of the two sources.

POWER FLUCTUATIONS: is a periodic dip or spikes in the electrical current of any given circuit.

POWER FAILURE: is a short- or long-term loss of the electric power to an area.

CONTACTOR: A contactor is an electrically-controlled switch used for switching an electrical power circuit.