Design And Construction Of An Automatic Changeover Switch Microcontroller And Switches

ABSTRACT

Power failure or outage in general does not promote development to public and private sectors. This paper presents the design and construction of an automatic power change-over switch that switches Power supply from main supply to another standby supply and it does this automatically using microcontroller. This device eliminates the challenge of a manual change-over system. This research covers the design and construction of a single phase microcontroller-based 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. This was achieved by the use of electrical components such as resistors, capacitors, diodes, transistors, opto-isolators etc., integrated circuits that have timing abilities and relays for switching effect. Due to the looping of the pole of the contactor to give 50A current each for PHCN and generator, the maximum power the circuit can withstand on an a.c voltage of 240V is 12KVA. This means the circuit can carry a large amount of power in homes and offices.

Key words: Single Phase Preventing, Switching, Microcontroller, changeover switch, changeover switch.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1     BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• AIM AND OBJECTIVES OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• APPLICATION AND ADVANTAGES OF THE PROJECT
• SCOPE OF THE PROJECT
• DEFINITION OF TERMS
• PROJECT ORGANISATION

CHAPTER TWO – LITERATURE REVIEW

2.1     OVERVIEW OF RELEVANT TECHNOLOGY

2.2     REVIEW OF EXISTING SYSTEM

2.3     REVIEW OF RELATED WORKS EXISTING SYSTEM

2.4      REVIEW OF FUNDAMENTAL CONCEPTS

2.5     DESCRIPTION OF A RELAY

2.6      HISTORY OF POWER FAILURE AND SYSTEM RELIABILITY

2.7      TYPES OF POWER FAILURE

2.8       PROTECTING THE POWER SYSTEM FROM FAILURE

2.9      REVIEW OF THE THREE DIFFERENT SUPPLIES

2.10    SUMMARY OF REVIEWED WORKS

CHAPTER THREE

3.0         METHODOLOGY

3.1        SYSTEM BLOCK DIAGRAM

3.2        SYSTEM FLOW CHART

3.3      SYSTEM CIRCUIT DIAGRAM

3.4       THREE-GANG SWITCH

3.5      CIRCUIT ANALYSIS AND CALCULATIONS

CHAPTER FOUR

4.0       RESULT ANALYSIS

4.1     RESULTS AND DISCUSSIONS

CHAPTER FIVE

• CONCLUSIONS
• RECOMMENDATION

5.3     REFERENCES

CHAPTER ONE

1.0                                                INTRODUCTION

1.1                                  BACKGROUND OF THE STUDY

An automatic power changeover system designed and implemented basically disconnects load from its power source and transfers it to a standby power source, in the advent of a power failure. This transfer is done at a very high switching speed such that minimal change occasioned by the transfer process goes unnoticed. It also incorporates a generator shutdown terminal that switches off the generator after the mains power supply has been restored. This process is controlled by a controller that keeps sensing to detect the availability of power supply on the Main supply line. The system is also fitted with an AC voltmeter that correctly reads the analogue voltage supplied by the power source and displays it on a seven segment display module. The power change-over switch is a device that detects when the electrical energy from the mains power supply is cut off and subsequently switching on the power generator. Basically it is aimed at switching on a more convenient power supply to the load. Since it switches on power to the load, precautions has to be taken while choosing the type of change-over switch, of power generator to supply electrical energy that would power their homes whenever the supply from the electricity company is cut off. A power change-over switch enables this transfer. Power change-over switches can be operated manually in order words whenever there is power failure, an individual can shift a handheld lever that would open contact on the main power supply line and close contact on the power generator line. This process consumes time and puts such an operator at risk of electrical hazards.

The research project is designed for power supply applications. It involves automatic change over between the mains power supply and a standby generating set. The project implements an automatic switching or starting of the power generator, whenever the main power fails. The circuit of the project consists of logical control units, display units, alarm units and relay switches. The design of the project takes into consideration practical or real life situations and a lot of precautions were put in place to make its performance acceptable, even though it is a prototype design. The basic operation of the project is to switch ON an auxiliary power supply (a generator). This operation connects the power supply from the generator to the load after a predetermined time interval. This is intended to normalize the current from the generator. Switching is possible through the use of the relays. The system was designed to automatically change power supply back to the main supply moments, after the A.C. mains are restored and to switch OFF the generator.

This project, however is designed and implemented as a micro-processor based controlled system, specifically using the micro-controller as its basic component and a 3-gang switch for switching on and off of flats. It is a dedicated embedded system

1.2                                   PROBLEM STATEMENT

In the last decay, switching from mains supply to solar inverter and vice –versa is done manually, and this involves labour, wastes time and at the same time can expose the operator to risk of electric shock. However, this device was invented to solve this problem, it switches automatically between the mains supply and solar inverter when the need arise.

1.3                    AIM AND OBJECTIVE OF THE PROJECT

The main aim of this project is to design a device that will provide uninterrupted power supply to a load, by selecting the supply source automatically from any available one out of two sources (main and generator) in other to ensure uninterruptible power supply. This is done by using microcontroller, relay, three-gang  switches and LCD. The objectives are:

1. To protect our devices from power interruption.
2. To protect our investment by ensuring a steady power supply

• To study relays and their connections

1. To supply power to more than one apartment

1.4                          SIGNIFICANCE OF THE PROJECT

This project provides an effective solution to provide an alternative power supply during frequent power cuts.

Building this device is a way of minimizing damage to lives/equipment since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error.

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.

1.5        APPLICATION AND ADVANTAGES OF THE PROJECT

1. This system could be used in that places where we have different sources of supply such as main and generator or solar.
2. This system could be used in industries for supplying the uninterruptable power supply to the industrial machines.
3. This system could be used in educational institutes and hospitals for supplying the uninterruptable power supply to the hospital or educational equipment.
4. This system is more compact and reliable as compared to the electrical ATS panels.
5. This system is less costly as compared to the other power control systems.

1.6                                  SCOPE OF THE PROJECT

The scope of this study covers building a microcontroller based changeover with 3 switches. A relay driver is used that receives microcontroller generated output and switches that particular relay to provide continuous power supply. The three gang switch used are used for manually supplying power to different apartment. When main fails to supply power, automatically next available source is used say generator. An LCD is also used to display which source is being currently used for power supply.

1.7                                                  DEFINITION OF TERMS

CHANGEOVER: Generally, a changeover 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 four 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.    

1.8                                        PROJECT WORK ORGANISATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this works is on the introduction to this study. In this chapter, the background, significance, objective limitation and problem of this study were discussed.

Chapter two is on literature review of this study. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.