Design And Construction Of A Contactor Based Automatic Transfer Switch For Three Phase

ABSTRACT

Constant supply of power is the wheel of growth to any nation’s economy. A country like Nigeria, where total power generation is less than one quarter of total demand, means of augmentation and smooth operation cannot be over emphasized. This paper presents a real laboratory design and construction of Automatic Transfer Switch (ATS) with three phase selector. The design method involves the use of contactors. The ATS designed demonstrates its ability to perform automatic power change over activities easily without any human interaction.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1      BACKGROUND OF THE PROJECT

• AIM/OBJECTIVE OF THE PROJECT
• PURPOSE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• SCOPE OF THE PROJECT
• PROBLEM OF THE PROJECT
• APPLICATION OF THE PROJECT
• PROJECT ORGANIZATION

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF THE STUDY
• OPERATIONAL REVIEW OF A TRANSFER SWITCH
• TYPES OF TRANSFER SWITCH
• MANUAL TRANSFER SWITCH OR CHANGEOVER SWITCH
• BENEFITS OF AUTOMATIC TRANSFER SWITCH OVER A MANUAL TRANSFER SWITCH
• PROTECTING THE POWER SYSTEM FROM FAILURE
• RESTORING POWER AFTER A WIDE-AREA OUTAGE
• DESCRIPTION OF A CONTACTOR
• DIFFERENCE BETWEEN A CONTACTOR AND A RELAY
• GENERAL APPLICATIONS OF CONTACTOR

CHAPTER THREE

METHODOLOGY

• WORKING PRINCIPLE
• SYSTEM CIRCUIT DIAGRAM
• DESIGN SPECIFICATION
• BASIC OPERATION OF A CONTACTOR
• CONTACTOR WIRING DIAGRAM
• CONTACTOR OPERATING PRINCIPLE
• HOW TO WIRE A CONTACTOR

CHAPTER FOUR

TESTING AND RESULTS

• CONSTRUCTION PROCEDURE AND TESTING
• INSTALLATION OF THE COMPLET DESIGN
• ASSEMBLING OF SECTIONS
• TESTING, TROUBLESHOOTING AND REMEDY
• ECONOMIC OF THE PROJECT
• PROJECT VIABILITY
• PROJECT RELIABILITY
• PROJECT MAINTAINABILITY
• PROJECT EVALUATION

CHAPTER FIVE

• CONCLUSION
• RECOMMENDATION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

In developing countries like Nigeria today, there is the problem of interrupted power supply as insufficient power is being generated to provide consumers with continuous services and satisfactory quality. This leads to constant power failure which in turn affects both the public and private sectors of the economy. Industries, banks, hospitals and so many other public and private establishment all have major critical loads that needs to be powered at all times in order to carry out various processes efficiently. This power instability now brought about the need to create an alternative means of power to back up the public utility supply. The introduction of some of these alternative sources of power supply brings forth the challenge of switching smoothly in a timely manner between the mains supply and the alternative sources whenever there is a failure on the mains source [3].

Automatic changeover switch is an integral part of the process of power generation, allowing smooth and instant transfer of electric current between multiple sources and load. The function of the automatic change over switch is to monitor the incoming public supply voltage and detect when the voltage drops below a certain level that electrical/electronic appliances can function depending on the utility supply. The automatic change over switch compares the voltage of the other two phases using a comparator circuit and if the voltages are not available, the system changes over from public supply to generator. When the generator is in operation, the transfer switch prevents any feedback current to the load. It also ensures that the different power sources are synchronized before the load is transferred to them. The transfer switch senses when there is interruption if the mains supply remains absent. The principle of the automatic change-over switch is such that it links the load and mains supply or the alternative supply together. This enables the use of either the mains supply or an alternative source when there is outage on the mains source which can either be a three phase or a single phase [1][2].

However, the automatic transfer switch embedded with a phase selector comprises of a monitoring unit which monitors the three phases and gives a single output as well as monitoring the output that comes from the generator, a control unit that controls the operation of the circuit.

1.1                                                 AIMS AND OBJECTIVES

The main objective of this work is design a device that when the utility power goes out, the transfer switch signals your generator to start. Once the generator is running the transfer switch automatically connects your home or business to the generator. When the utility power is restored, the transfer switch reconnects your home or business to the utility [2].

At the end of this work student involved shall be able to:

1. design this device using contactors
2. understand how the device works
3. understand the wiring and operation of a contactor.

1.2                                              PURPOSE OF THE PROJECT

Due to inconsistent supply of power, there is a growing need for an alternative source of power supply. This has lead to heavy capital investment in a bid to suppress power failure and ensure regular power supply for the industry, hospitals, schools and homes. The purpose of the study is to solve the problem of power failure can be checkmated with the use of stand-by generating set.

1.2                                         SIGNIFICANCE OF THE PROJECT

• Automatic Transfer Switches are used to insure the continuity of power supply, although this can mean different things in different situations. In a typical home, small business or institution, continuous power may mean that a short interruption can be tolerated. For example, if a backup generator is used to supply backup power when public utility power fails, there will be a pause while the generator starts up. In a hospital any interruption of more than a few seconds may be catastrophic. There are several ways that ATS can insure that the interruption is very brief — including batteries to fill in the gap from the cessation of public utility power to the start of backup generator supply. Some automatic switches sense the temporary dips and spikes in public utility power that precedes failure and starts up the generator before the complete failure of public power.
• It reduces its change over timing to the minimum due to its fast response to power outage.
• It maintains high quality of service through its fast and prompt response.
• Moreover, the size and captivity of the unit will depend upon the load for which it will be used. The unit is also portable, easy, convenient and safe to install.

1.3                                     STATEMENT OF THE PROBLEMS

In every home, office or industries, automatic power changeover  plays a vital role, that is, It provides a means of switching from utility AC mains to generator in the case of power failure; 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:

• Difficulty in troubleshooting with circuit without the circuit diagram
• Difficulty in connecting the output without short-circuiting, until a multiplexing circuit was gotten.
• Difficult in wiring because of the strong wiring the project required.

1.4                                                SCOPE OF THE STUDY

It has a simple intuitive control panel, which allows the flow of mains electricity to pass by unhindered, until such time that the mains supply fails and a generator is needed to take over the supply of power. A transfer switch is an electrical signalling system that tells the generator that it is needed and switches a load between two sources. An automatic switch will sense when one of the sources has lost or gained power, and automatically kick the generator into life – or shut it down once power has been restored – to keep your home or small appliances running as normal.

The Phase is a highly configurable three-phase ATS auto changeover switch. This automatic transfer switch is designed to automatically start your 3 phase generator and then transfer power from the mains supply to a three-phase and compatable diesel generator, through to your distribuition board in the event of a powercut.

 1.5                                         APPLICATION OF THE PROJECT

Some common examples of entities that implement automatic switches out of necessity are: hospitals, data centers, jails and prisons, fire departments, defense organizations, and police departments.

1.7                                              PROBLEM OF THE PROJECT

May occasionally respond to false signals: When an automatic switch senses signals in a building’s primary power supply that seem to indicate an impending power outage, it switches the building from utility feed to generator feed to avoid the coming outage. However, some transfer switches have been known to respond to false signals, a scenario that could waste generator power, albeit in small amounts.

Usually costs more than a manual model: Because automatic models are generally larger and contain more complex components than manual models, they usually cost more. However, their price tag varies according to the style of switch a building needs and what brand is purchased. An emergency power solutions provider is the best entity to consult about switch choice.

Needs more maintenance than a manual model: Manual models typically involve less maintenance because they involve less complex components, particularly in terms of testing maintenance and replacement parts. An emergency power solutions provider is the best entity to consult about transfer switch maintenance.

1.8                                           LIMITATION OF THE PROJECT

• It requires maintenance because they involve less complex components, particularly in terms of testing maintenance and replacement part.
• The cost of designing the device is higher the parts are higher than that of the manual transfer switch.
• Transfer 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.
• Operating voltages: 220V-240
• 60A is the maximium load it can handle.

1.9                                                  DEFINITION OF TERMS

CONTACTOR: contactor is an electrically-controlled switch used for switching an electrical power circuit. A contactor is typically controlled by a circuit, which has a much lower power level than the switched circuit, such as a 24-volt coil electromagnet controlling a 230-volt motor switch.

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.