Design And Construction Of A 60A Three Phase Automatic Changeover Switch

ABSTRACT

This project work is on the design and construction of a 60A automatic changeover for 3-phase power supply. It provides a means of switching from one phase of AC mains to another in the case of failure in the existing phase; This project has been improved on the existing types of electromechanical device that has being in use over the years.

Hence this has been achieved by the use of operational amplifier, timing circuit and high current relay switches and it is powered by 12V dc power supply.
The aim of this work is to design and construct an Auto changeover introduces an automatic solution to overcome power fluctuation/phase interruption by selecting next most healthy available phase to feed the equipment without any notice of power outage.

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• AIM/OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION OF THE PROJECT
• LIMITATION OF THE PROJECT
• ADVANTAGES OF THE PROJECT
• SCOPE OF THE PROJECT

CHAPTER TWO

LITERATURE REVIEW

 2.1       REVIEW OF CHANGEOVER

2.2       HISTORICAL BACKGROUND OF AN AUTOMATIC CHANGEOVER

2.3    REVIEW OF ELECTRICAL PHASES

2.4     REVIEW OF THREE-PHASE ELECTRIC POWER

2.5     POWER SUPPLY UNIT

2.5.1 THE RECTIFYING UNIT

2.5.2 THE SMOOTHING UNIT

2.5.3 THE REGULATOR AND REGULATED

CHAPTER THREE

3.0     CONSTRUCTION METHODOLOGY

3.1     BLOCK DIAGRAM OF THE SYSTEM

3.2       CIRCUIT DIAGRAM

3.3       CIRCUIT DESCRIPTION

3.4       SYSTEM OPERATION

3.5       DESCRIPTION OF MAJOR COMPONENTS USED

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 OPERATION OBSERVATIONS

4.6     DIFFICULTIES ENCOUNTERED ON THE SYSTEM

4.7      PICTURE OF THE SYSTEM AFTER CONSTRUCTION

4.7      COST OF PRODUCTION

CHAPTER FIVE

• SUMMARY
• 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.

1.2                                   PROBLEM STATEMENT

Power failure or outage in a country, state or city is highly detrimental to development in public and private industries. The insecurity associated with constant or frequent power failure or outage brings about limitation to power  consistent investments, thus hampering the development of industries and multinational ventures. Processes like carrying out surgical operations in hospitals, laboratories which require constant power supply for research, money transactions  between banks and more require constant use of uninterrupted power. In other to solve this problem, an automatic changeover switch was invented. This research covers the design and construction of a single phase digital automatic power changeover. It has the capacity to automatically switch power from  national grid to generator and vice versa, once there is power failure in any of the two power supplies and at the same time has the capacity of shutting down a generator set once the mains grid is been restored.

1.3                                          OBJECTIVE OF THE PROJECT

The objective of this work is to design a device that will overcome power fluctuation phase interruption by selecting next most healthy available phase to feed the equipment. This device is capable of handling load up to 60A and the switching device (relays) are rated 60A.

1.4                             PURPOSE OF THE PROJECT

The purpose of the project is to provide the supply for the single phase load from the one of the active phase of the 3-phase supply but if there is power failure in the three phases the device will switch over to generator set.

Another purpose of this work is to provide a constant power supply to consumers.

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 phase selector unit for those equipment whose supply is single phase. The single phase supply is selected automatically from three phases supply.

Auto changeover introduces an automatic solution to overcome power fluctuation \ phase interruption by selecting next most healthy available phase to feed the equipment.

1.6                        LIMITATION OF THE PROBLEMS

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 phase; 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 the three phases short-circuiting, until a multiplexing circuit was gotten.
• Difficult in wiring because of the strong wiring the project required.
• 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 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.
• Operating voltages: 220V-240
• 60A is the maximium load it can handle.

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.

RELAY: relay is one of the major components used in this work which is an electrical device, typically incorporating an electromagnet, which is activated by a current or signal in one circuit to open or close another circuit.

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.