Design And Construction Of An Automatic Change Over Switch Using Smart Timing And Voltage Regulator

ABSTRACT

The Changeover Switch is a device used to switch off a power supply and subsequently switch on another power supply.

An automatic changeover Switch was invented due 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. 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

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE PROJECT
• PPROBLEM STATEMENT
• AIM/OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• PURPOSE OF THE PROJECT
• LIMITATION OF THE PROJECT
• APPLICATION OF THE PROJECT
• DEFINITION OF TERMS
• PROJECT ORGANISATION

CHAPTER TWO

LITERATURE REVIEW

2.0     LITERATURE REVIEW

2.1     REVIEW OF ELECTRICAL PHASES

2.2     REVIEW OF RELATED PROJECT

2.3     REVIEW OF THREE-PHASE ELECTRIC POWER

2.3      REVIEW OF CAUSES OF POWER FAILURES

2.4       POWER SUPPLY RELIABILITY

CHAPTER THREE

3.0   METHODOLOGY

3.1 INTRODUCTION

3.2 BLOCK DIAGRAM

3.3 FLOW CHART

3.4 CIRCUIT DIAGRAM

3.5 CIRCUIT ANALYSIS AND CALCULATIONS

CHAPTER FOUR

4.0       RESULT AND DISCUSSION

CHAPTER FIVE

• CONCLUSIONS
• RECOMMENDATION

5.3     REFERENCES

CHAPTER ONE

• INTRODUCTION

A power changeover circuit for selectively connecting an electrical load to one of two available power sources, preferably alternating current sources, wherein one of the sources constitutes an engine driven generator requiring a predetermined time to reach specified output characteristics after it energizes. Relay operated changeover switch means selectively connects the load to either of the electrical power sources, and second switch means in series with the changeover switch located between the changeover switch and the engine driven power source delays connected of the generator source with the load after disconnection of the load from the other source until the generator output reaches specified characteristics. Further, the circuit provides for the disconnection of the load from the generator upon deenergization of the generator, and prior to the changeover switch connecting the load to the other supply source in order to prevent arcing. Relays, resistors and time delay switch devices are utilized in the circuit to provide the desired operation

1.1                           BACKGROUNDOF THE PROJECT

The need for constant and stable power supply in a country, state or city cannot be overemphasized. In most developing nations, industries, firms and organizations contest for power supply that is unreliable and insecure, thus marring the effect of productivity and development. In these nations, the quest for secure and reliable power supply remains a dream yet to be achieved. This is as a result of increase in population, industrialization, urbanization (Aguinaga, 2008; Fuller, 2007; Kolo, 2007) and lack of proper planning by the government and utility providers. Most manufacturing industries, firms and institutions such as hospitals and healthcare facilities, financial institutions, data centers and airports to mention, but a few require constant power supply throughout the year. Volatility in power generally delays development in public and private section of any economy (Kolo, 2007; Anon, 2010; Chukwubuikem, 2012). For instance, power failure could lead to prohibitive consequences ranging from loss of huge amounts of money to life casualties (Aguinaga, 2008).

This instability in power supply has led to the development of switching systems between national grid power system and standby generators used as backup. In the past decade, various equipment and configurations have been put in place in order to manage this problem (Aguinaga, 2008). An automatic changeover switching system makes use of contactors, active and passive components and transducers to realize changeover in a shorter time while excluding human interference and its attendant (Chukwubuikem, 2012).

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 aimed at building a micro-processor based automatic changeover switch with timing and voltage regulating features.

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 an automatic power changeover. It has the capacity to automatically switch power from national grid to generator and vice versa.

1.3                                   AIMS AND OBJECTIVES

The main aim of this work is to build a micro-processor based automatic changeover switch with timing and voltage regulating features. The objectives are:

1. to provide uninterrupted power supply at all times to all its consumers
2. to build a device which switches on the head from power Holding Company (PHC) to a generator when power fails and from generator to PHC when power comes back, using timing, switching and regulating device.

• To supply a regulated voltage to the user.

1. To minimize damages to lives/equipment since it has its own monitoring system and its switching requires no human contact with the switch, thus eliminating human error.
2. To reduce change over timing to the minimum due to its fast response to power outage.

1.4                                BENEFIT OF THE PROJECT

The automatic change over switch has the following advantages;

• 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.
• It can operate in low voltage.

1.5                           PROBLEMS OF THE PROJECT

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.

1.6                SCOPE AND LIMITATION OF THE STUDY

This work covers only a one phase automatic changeover which can only be used for providing a means of timing, relating and switching from one phase of AC mains to another in the case of failure in public utility. It is limited to

•  Phase – one phase
• Capacity – single Phase
• Input Volt – 220v

1.7                                      APPLICATIONS OF THE PROJECT

This device can be used in places such as:

1. Homes
2. Offices,

• Worship centres

1. Industries
2. This circuit can be used as a home lighting system with few modifications.
3. It can be used to drive other DC loads like a DC motor of any electronic appliance or other toy applications.

1.8                                            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.    

1.9                          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 changeover switch. In this chapter, the background, significance, objective limitation and problem of changeover switch were discussed.

Chapter two is on literature review of changeover switch. 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.