A UPS system is a DC to AC conversion system of 1KVA power rating and expected to carry around 800 watts load. It provides power to electronic and electrical appliances such as radio sets, TV DVD/VCD, computers, fans and lighting. The design was conceived and put down as block diagram. Corresponding circuit diagrams for each black box were sourced and drawn. The component values according to desired specifications were designed from the first principle and needed values derived. The transformer was also designed and with measurements and component values we went to the market. Most of the transistors were not in the market and order was made with the trader and they were later collected. These components were first wired on project board, tested before being removed and transferred to veroboard where they were soldered permanently and tested. The tests carried out were successfully including the capacity of the transformer and the transformer stability and hum-free operation. The circuit veroboard and transformer along with meters, switches, indicators and output sucket were all carefully packaged inside the system box and test carried out again. This financial test was also successful.

TABLE OF CONTENTS

Title Page

Title Page i

Certification ii

Dedication iii

Acknowledgement iv

Abstract v

Table of Contents vi

List of tables ix

List of Figures x

List of Appendices ix

CHAPTER ONE

INTRODUCTION 1

1.1 The Background of the Problem 1

1.2 The Purpose/Objective/Aim of the Project 2

1.3 Scope of the Project 3

1.4 Limitation of the Study 4

1.5 Definition of operational Terms: 5

CHAPTER TWO

LITERATURE REVIEW 9

2.1 Feedback Oscillator principle 10

2.2 Astable Multivibrator Principle 11

2.3 Field Effect Transistor (FET) 14

CHAPTER THREE

DESIGN METHODOLOGY 18

3.1 Block diagram/flow chart of UPS 19

3.2 Specification 20

CHAPTER FOUR

ANALYSIS AND DESIGN 21

4.1 Voltage regulator/monitor 21

4.2 UPS circuit 23

4.3 Low pass filter 25

4.4 Pre-amplifier 26

4.5 Buffer amplifier 28

4.6 Power amplifier 30

4.7 Heat sink 32

4.8 UPS transformer design 32

4.9 Complete circuit diagram of 1kva ups system with built 12VDC battery 44

CHAPTER FIVE

PRESENTATION AND ANALYSIS OF RESULT 45

5.1 Construction, testing and packaging 47

CHAPTER SIX

CONCLUSION AND RECOMMENDATION 52

6.1 Conclusion 52

6.2 Recommendation 52

References 54

Appendix I 55

Appendix II 57

LIST OF TABLES

Table 4.1: Coefficient of Utilization 35

Table 4.2: Calculated Winding Parameters 39

Table 5.2: BEME 45

LIST OF FIGURES

Fig 2.1: Feedback Oscillator Principle 10

Fig 2.2: Astable Multivibration Circuit 11

Fig 2.3: Symbol of an Enhancement Channel (MOSFET) 15

Fig 2.4: MOSFET Power Transistor Schematic 17

Fig 2.5: Symobl of MOSFET 17

Fig 3.1: Block Diagram 19

Fig 4.1: Voltage Regulator/Monitor 21

Fig 4.2: UPS Circuit 23

Fig 4.3: Equivalent Circuit of T₂ Showing the Origin of Overshoot 24

Fig 4.4: Cascaded Low Pass Filter 25

Fig 4.5: Pre-Amplifier 26

Fig 4.6: Buffer Amplifier 28

Fig 4.7: Darlington Pair Power Amplifier 30

Fig 4.8: Output Stage 31

Fig 4.9: Transformer Schematic Diagramme 33

Fig 4.10: Transformer Turns Schematic Diagramme 35

Fig 4.11: Sketch of Transformer Core Lamination 41

CHAPTER ONE

INTRODUCTION

1.1 The Background of the Problem

Uninterrupted Power Supply (UPS) system is a unit developed for the conversion of direct current (DC) into alternating current (AC) to serve electronic and electrical appliances, such as radio sets, television sets, DVD/VCD, computer, photocopying machine etcetera and also provide lighting and power to fans. UPS systems could be used in conjunction with the solar energy conversion system for the harnessing of solar power energy and also as vital part of uninterrupted power surprise system.

The concept and development of UPS system because necessary of the poor national power supply system that resulted in incessant power supply and power outages. UPS is also found in use where there is no supply of electricity in the first place.

1.2 The Purpose/Objective/Aim of the Project

The purpose of the project is to design and construct a 1KVA UPS system for the supply of A.C power to serve load of about 800watts power (the active or real power, 1KVA x 0.8 = 800 watts).

The objective of the project is to ensure that the research produce an inverter and step-up transformer that would be able to transform few D.C voltage of about 12 voltage to up to 220 volt A.C 50Hz obtainable from the national power supply. Electronic appliances designed and constructed for use in Nigeria are meant to work at the designed specification of 220/230 Volt AC, 50Hz in contrast to similar equipment meant to work in a country like Japan whose national electric power supply is 110 volt A.C., 60Hz.

The designed and constructed UPS system in accordance with the specification of national power supply will not discriminate against any equipment nor serve only a particular electronic appliance. The UPS system will be universally accepted by any system operating in Nigeria or in countries that adopted same specification. By this, the aim of the project design and construction must have been achieved.

1.3 Scope of the Project

This project is on the design and construction of 1KVA UPS system with an in-built battery supply. In the first place, the 12 VDC battery is not part of the system to be designed implemented. The scope of the project includes designing and deriving the component values of all the circuits involved for the implementation of this project. These components are sourced and fixed in the vero board according to the determined circuitry, wired and tested through. The circuitry is completed by the design of transformer laminations and coils or windings, packaging and clamping of these laminations to air tight condition and testing through to ensure the specified rating of 1KVA which will supply a real power of 1KVA x 0.8.

The scope of the project also converted testing of the entire system after packaging in a metal construction with vent that will ensure in-let of air as coolant to the transformer that is expected to generate heat while in operation including power transistors.

The UPS system produced cannot work along wired installation of power supply from the national grid unless other units are incorporated. It works on stand alone bases where no power was extended from the national into operation intermittently.