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DESIGN AND CONSTRUCTION OF 2KILOWATTS POWER INVERTER FOR FARM HOUSE USE BY OLALUSI, Oluwaseyi Gabriel (AGE / 03 /1304) FEDERAL UNIVERSITY OF TECHNOLOGY AKURE FEBRUARY, 2010

DESIGN AND CONSTRUCTION OF 2KILOWATTS POWER INVERTER FOR FARM HOUSE USE

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The importance of electricity to farm techniques in the present day cannot be over emphasized. Hence, 2Kilowatts power inverter was designed, constructed and tested. The project is about power supplies and conversion from one form to another i. e. Direct Current to Alternating Current. This is to deal with the erratic power supply to rural area and improve social well being of rural people, and salvage the urban-drift and make farming business attractive and interesting. The methodology used to achieve the objectives focused on the design of transformer as the main integral part of the inverter. The design and selection of other components were based on their availability, durability, affordability, thermal and electrical properties. The inverter was designed, developed and tested. It is 12-pulse inverter i.e. consist of 12 IRFP 260N FETS transistors to supply electric power similar to the power grid of sinusoidal waveform. The evaluation of the inverter was carried out in the electrical workshop of Don Bosco Technical institute of Electrical Engineering and Maintenance, Akure. The results obtained show that the inverter has nominal AC output Voltage is 220Vac; Ac operating voltage Range from 220 –240Vac; Nominal AC Frequency is at 49.5Hz ; Maximum AC output Current is 9.2Aac as against 9.91Aac calculated; maximum AC output Power is 2,024Watts as against 2,181Watts designed for. It has 93% efficiency. It was tested as independent unit of power supply with forgo lead-acid battery product of 12V, 200Amperes Hour against idling; non-compressive and compressive loads. From the graphic analyses, it shows that the inverter consumed little battery energy when no load is applied; while on non-compressive loads, it consumed 54.8% of the total battery charges within 4hours of test period. 63.6% of the battery energy was consumed when on compressive loads for 3hours test period. This shows that the power factor of compressive loads is greater and the use of the lead-acid battery to supply energy to the inverter to power compressive load will drain maximum current from it within the period of use. There was also significant disparities in the percentage of energy reservoir between the model equation results and the obtained results on the tables 4.2 and 4.3 with their graphical analyses further explained that the lead-acid battery components are deteriorating internally when is used as energy reservoir for inverter to power non-compressive and compressive loads.. The primary source of energy i. e. lead-acid battery is not rich enough to provide the needed energy to power the selected loads such as compressive and non-compressive more than of 3-4hours. The loads are selected based on the energy reservoir of the battery. The results also show that constant discharge of the lead-acid battery beyond 50% DOD will deteriorate it and shorten the life span.

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Page 1: DESIGN AND CONSTRUCTION OF 2KILOWATTS POWER INVERTER FOR FARM HOUSE USE

DESIGN AND CONSTRUCTION OF 2KILOWATTS POWER INVERTER FOR

FARM HOUSE USE

BY

OLALUSI, Oluwaseyi Gabriel (AGE / 03 /1304)

FEDERAL UNIVERSITY OF TECHNOLOGY AKURE

FEBRUARY, 2010

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ii

DESIGN AND CONSTRUCTION OF 2000WATTS POWER INVERTER FOR FARM HOUSE USE

BY

OLALUSI, OLUWASEYI GABRIEL (AGE / 03 /1304)

A Project in the Department of Agricultural Engineering submitted to the School

of Post Graduate Studies in partial fulfillment of the requirement for the award of

Post Graduate Diploma (PGD) in Agricultural Engineering.

FEDERAL UNIVERSITY OF TECHNOLOGY AKURE

FEBRUARY, 2010

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CERTIFICATION

This is to certify that that this work was carried out by Mr. Olalusi Oluwaseyi Gabriel with

matriculation number AGE/03/1304 in the department of Agricultural Engineering in the school of

Engineering and Engineering Technology, Federal University of Technology Akure, Ondo State,

Nigeria. In partial fulfillment of the requirement for the award of Post Graduate Diploma (PGD Eng) in

Agricultural Engineering of the Federal University of Technology Akure, Ondo State, Nigeria.

This work has not been submitted elsewhere for the award of any other degree or diploma.

……………………………. ………………………………… Dr F. R. Falayi Date Project Supervisor

……………………………… …………………………………

Prof. L. A. S. Agbetoye Date HOD

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DEDICATION

This project work is dedicated to my late mother

Mrs Elizabeth Adekunbi Olalusi

(A’yinke – Ade)

Nee Fowowe

Died on 17th March, 2006

Aged 57years

And

To all women who suffer daily from domestic violence in the world

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ACKNOWLEDGEMENT I owed it all to the Almighty God for His mercies, protection, provision and strength for the

successful completion of my Post Graduate Diploma Programme, I am forever grateful.

I gratefully acknowledged my Project supervisor, Dr F. R. Falayi, for his patience, moral

support; encouragement and advice, in making this project a reality. Also to my students and friends of

mine Ajetomobi Muyiwa and Lekan Omoniyi, for their creativity minds and encouragement, in making

the project a reality. My prayer is that God in His infinity mercy will amply bless them.

I will remain ever grateful to my lovely late mother, Princess E. A. Olalusi, for the support she

gave me during her short time on earth. May her soul spirit rest in peace, amen.

To my siblings, Sister Dele, Wale, Foluso, Funbi, and Busayo, I say thank you for your support

and encouragement, I am very grateful. Also to my little girls, Seyi and Sola, God bless you amen.

To my PGD colleagues, Mr. Esho Kola, Mr. Ajayi ‘Dipo, Mrs Ebietomiye, Mrs Helen Adefioye, Mr.

Faniyi Victor, Mr. Olayemi, Mr. Felix Osu, Mr. Abe, Mr. Ahmed, Mr. Mayaki, Mr. Lasisi; I say God

bless you all amen. And Mr. Godwin Aduku Ukwenya, whose encouragement and persuasion help me

to complete this project. My sincere appreciation goes to entire management, staff and students of Don

Bosco Technical Institute of Electrical Engineering and Maintenance for their supports. It was there

that I conceived this technological idea which has made many of their students to be self-reliance. To

Rev. Fathers Stephen Omoniyi and Joe Gyamfi, God will increase you more and sustain you in His

vineyard, amen. To Mr. Apotiade, Mrs Adeuyi B., Gbenga Bambe and Mr. Abiodun Abimbola, I say

thank you for moral and financial supports. A big thanks to my father, Mr. Olalusi, M. I. for his

support, may he live long to reap the fruits of his labour, amen.

Finally, special encomium to my love and angel; Mofifoluwaso, “there is nothing better than

the encouragement of a good friend”. I will always love you.

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ABSTRACT

The importance of electricity to farm techniques in the present day cannot be over emphasized.

Hence, 2Kilowatts power inverter was designed, constructed and tested. The project is about power

supplies and conversion from one form to another i. e. Direct Current to Alternating Current. This is to

deal with the erratic power supply to rural area and improve social well being of rural people, and

salvage the urban-drift and make farming business attractive and interesting.

The methodology used to achieve the objectives focused on the design of transformer as the

main integral part of the inverter. The design and selection of other components were based on their

availability, durability, affordability, thermal and electrical properties. The inverter was designed,

developed and tested. It is 12-pulse inverter i.e. consist of 12 IRFP 260N FETS transistors to supply

electric power similar to the power grid of sinusoidal waveform.

The evaluation of the inverter was carried out in the electrical workshop of Don Bosco

Technical institute of Electrical Engineering and Maintenance, Akure. The results obtained show that

the inverter has nominal AC output Voltage is 220Vac; Ac operating voltage Range from 220 –

240Vac; Nominal AC Frequency is at 49.5Hz ; Maximum AC output Current is 9.2Aac as against

9.91Aac calculated; maximum AC output Power is 2,024Watts as against 2,181Watts designed for. It

has 93% efficiency. It was tested as independent unit of power supply with forgo lead-acid battery

product of 12V, 200Amperes Hour against idling; non-compressive and compressive loads. From the

graphic analyses, it shows that the inverter consumed little battery energy when no load is applied;

while on non-compressive loads, it consumed 54.8% of the total battery charges within 4hours of test

period. 63.6% of the battery energy was consumed when on compressive loads for 3hours test period.

This shows that the power factor of compressive loads is greater and the use of the lead-acid battery to

supply energy to the inverter to power compressive load will drain maximum current from it within the

period of use.

There was also significant disparities in the percentage of energy reservoir between the model

equation results and the obtained results on the tables 4.2 and 4.3 with their graphical analyses further

explained that the lead-acid battery components are deteriorating internally when is used as energy

reservoir for inverter to power non-compressive and compressive loads.. The primary source of energy

i. e. lead-acid battery is not rich enough to provide the needed energy to power the selected loads such

as compressive and non-compressive more than of 3-4hours. The loads are selected based on the

energy reservoir of the battery. The results also show that constant discharge of the lead-acid battery

beyond 50% DOD will deteriorate it and shorten the life span.

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TABLE OF CONTENTS

TITLE PAGE

Title page ii

Certification iii

Dedication iv

Acknowledgement v

Abstract vi

Table of contents vii

List of Figures x

List of Tables xi

List of Plates xii

CHAPTER ONE

1.0 INTRODUCTION

1.1 Background 1

1.2 Justification of the study 2

1.3 Objectives of the study 3

CHAPTER TWO

2.0 LITERATURE REVIEW 4

2.1 Solar energy utilization 4

2.2 Generation of electricity 4

2.3 Power Supply 5

2.4 Power conversion 7

2.4.1 AC-DC converters (Rectifiers) 7

2.4.2 AC in, AC out: frequency changer; cycloconverters 7

2.4.3 Dc In, Ac Out: inverter (Electrical) 8

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Basic inverter circuit designs: 9

Inverter output waveforms: 10

More advanced inverter designs: 12

2.4.4 DC - to -DC converters 12

Buck converter: 13

Boost converter: 14

Buck-boost converter: 14

2.5 Electrical Properties of materials in inverters 15

2.5.1 Power semiconductor devices 15

Thyristor and Triac: 15

Gate Turn-Off thyristor (GTO): 16

Reverse-conducting thyristor (RCT) and

asymmetrical silicon-controlled rectifier (ASCR): 18

Power transistor: 18

Power Mosfet: 19

Insulated-gate bipolar transistor (IGBT): 21

MOS-controlled thyristor (MCT): 22

2.5.2 Transformer 25

2.5.3 Capacitor 27

2.5.4 Resistor 27

2.5.5 Integrated circuit (IC) 27

2.5.6 Buzzer 28

2.5.7 Diode 28

2.5.8 Light emitting diode (LED) 28

2.5.9 Relay: 28

2.5.10 Battery: 28

2.5.11 Heat sink 29

2.5.12 Vero board 29

2.5.13 Wire: 29

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2.5.14 Metal casing 30

2.5.15 Oscillator 30

2.6 Domestic electric power consumption 30

CHAPTER THREE

3.0 METHODOLOGY 31

3.1 Description and working principles of 2KW Inverter 31

3.2 Design consideration for 2KW Inverter 32

3.3 Design calculation for 2KW Inverter 33

3.4 Material selection for the components 35

3.5 Assembly of components 37

3.6 Evaluation of the device 39

a. Continuity test 39

b. Test without load 39

c. Test with non-compressive load 40

d. Test with compressive load 40

CHAPTER FOUR

4.0 RESULTS AND DISCUSSION 43

4.1 Continuity test 43

4.2 Test without load 43

4.3 Test with non-compressive load 45

4.4 Test with compressive load 47

CHAPTER FIVE

5.0 CONCLUSION AND RECOMMENDATION 49

5.1 Conclusion 49

5.2 Recommendation 50

References 51

Appendix A 52

Appendix B 53

Appendix C 59

Appendix D 60

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LIST OF FIGURES

Figure Title Page

2.1 Solar utilization. 6

2.2 Power Converter Family Tree 6

2.3 Simple inverter circuit shown with an electromechanical switch

and with a transistor switch 11

2.4 Square waveform with fundamental sine wave component,

3rd harmonic and 5th harmonic 11

2.5 DC-DC converter configurations: (a) buck converter;

(b) boost converter; (c) buck-boost converter 13

2.6 (a) Thyristor symbol and (b) volt-ampere characteristics 17

2.7 (a) Triac symbol and (b) volt-ampere characteristics 17

2.8 (a) GTO symbol and (b) turn-off characteristics 17

2.9 A two-stage Darlington transistor with bypass diode 19

2.10 Power MOSFET circuit symbol 21

2.11 Non-punch-through IGBT, (b) Punch through IGBT,

(c) IGBT equivalent circuit 24

2.12 Circuit schematic for P-MCT 24

2.13 Current and future power semiconductor devices development direction 24

2.14 Transformer diagram 25

3.1 Schematic Diagram of 2,000 Watts Inverter Circuit 34

4.1 DOD against test-time without load 44

4.2 DOD against test-time on non-compressive load 46

4.3 DOD against test-time on non-compressive load 48

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LIST OF TABLES

Table Title Page

3.1 The details of items designed 33

3.2 The electrical materials selected for the development of 2,000Watts Inverter 35

3.3 The electrical power of the non-compressive loads applied and running test period 41

3.4 The electrical power of the compressive loads applied and running test period 41

3.5 Bill of Materials 42

4.1 The result of idling load against DOD 60

4.2 The result of non-compressive load against DOD 60

4.3 Values of electrical properties of 2,000Watts Inverter 61

4.4 The result of compressive load against DOD 60

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LIST OF PLATES

Plate Title Page

3.1 Assembled components of Inverter circuit 38

3.2 The connection of Inverter to 12V, 200AH battery 38

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CHAPTER ONE

1.0 INTRODUCTION

1.1 Background

The use of energy by man for his sustenance and well being has increased ever since he came on

earth a few million years ago. Man requires energy primarily in the form of food he ate and to provide

for his shelter. With passage of time, the domestication and cultivation of animals and plants were aimed

at ensuring that his need was met and he also began to use wind for sailing, driving windmill and the

power of falling water to turn wheels. Agriculture has been the centre of man’s interaction and economy

activities and also his energy source; is clean and renewable.

Agricultural production presents many engineering problems and opportunities. Agricultural

operations which include, farm structure and its comfort, soil conservation and preparation, crop

cultivation and harvesting, animal production and commodities, transportation, processing, packaging

and storage, and critical factors of time and place. With the challenges of food and fibre production and

processing and sustaining them, started industrial revolution. It is worth saying that agriculture is mother

of all profession.

The industrial revolution brought many changes, the much needed flexibility in man’s movement,

with the use of fossil fuels, this made energy portable. This flexibility was further enhanced with

discovery of electricity for processing of food, communication and the development of control power

generating station using either fossil fuels, or water or wind. This has led to a better quality life and

integrated unit of human’s life. Electric power has had an impact on modern agriculture i.e. improving

conditions of faming business and saves time and labour.

The use of energy cannot be emphasised and there is urgent need to bring about the balance in

energy budget to meet effectively the need of the people both in rural and urban areas. We live in an era

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where we have a greater understanding that the effects of the way we generate our electricity represents a

clear and present treat to our environment and to us.

Of all the electric power generation sources, the solar appears to be:

i. Environmental friendly

ii. Inexhaustible and free

iii. Cost effective.

The use of solar energy has also make substantial progress in the realm of technologies since the

primitive man to the present time in the remote villages i.e. drying of farm products, cloth, and food

preservation etc. The power from the sun intercepted by the earth is approximately 1.8 x 1011 MW

(Sukhatme, 1984) which is larger than present consumption rate of all commercial energy sources. Thus

in principle, solar energy could supply all the present and future energy needs of the world on continual

basis.

However, the main problems associated with its uses, is that, it is diluted source of energy and

variation in availability occurs daily because of the day – night cycle i.e. earths orbits around the sun.

With all these it can still bring about the much needed balance in the energy usage and can be used in

stabilizing power supply.

1.2 Justification of the Study

As the condition of farming business improved, with the flexibility of electricity in other

advanced countries, the same cannot be said of the developing countries most especially Nigeria. The

versatility of electricity has led to high technology which it’s many interlocking influences shape

ambitions, mould ways of seeing things and sway choices of where in the world one is to work. The

main cause for mass rural urban drift. People are also attracted and held fast by better houses, hospitals,

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schools, communication, recreation, facilities for work, salaries and career prospects have drawn many

people away from rural area to urban and international centres and made farming business less attractive.

In rural area, despite the fact that machines are made available but the power to keep it working is

not available. Though electric power generator serves as complement of energy source but the running

cost is too great for rural people to afford. While scarcity and hike in fuel price in this country, Nigeria,

is at increase. The hike in fuel price between the period of early 1980’s and 2007 is 35,000 percent i.e.

from 20K to N 70.00K per litre (Olaitan and Omoniy,i 2007). This shows a great reliance on fossil fuels,

which does not really help rural people/dwellers and nation’s economy at large and the energy sector

should not be all about income accrued from oil only but using energy sources to sustain human

comforts. Also not all rural communities are connected to the power grid operated by the Power Holding

Company of Nigeria (PHCN) and few that were connected do not enjoy constant electricity supply due

to epileptic situation of the company.

There is an urgent need to meet rural in–house electric supply and improve social well being of

rural people, and salvage the urban-drift and make farming business attractive and interesting. The need

for electric supply is high; the use of renewable energy such as sun and wind can generate electricity for

rural area people and make them self independent. What is needed for wind as well as solar is a way to

store a large energy surplus. Technology already exist to turn it into fuel such as ethanol or banking

energy (battery) that can later churn out electricity.

1.3 OBJECTIVES OF THE STUDY

1. to design and construct power inverter for farm household electricity use based on

renewable energy source.

2. to carry out the performance evaluation of such device.

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CHAPTER TWO

2.0 LITERATURE REVIEW

2.1 Solar energy utilization

The intensity of solar radiation from the sun can be utilized in a variety of ways either by man or

nature. This can be grouped under two conversion methods i.e. direct methods and indirect methods by

which solar energy can be utilized for its heat and power. The figure 2.1 illustrates the two conversion

methods of solar energy:

2.2 Generation of electricity

Generation of electricity for the purpose of powering human technologies has been going on for at

least 120 years from various sources of energy. Electricity generation is the first in the processes of

delivery of electricity to consumers which also include processes such as electric power transmission and

electricity distribution. The first electrical power plants were run on woods, while today we rely mainly

on coal, nuclear, natural gas, hydro-electric dam and petroleum power and small amount from solar

energy (photovoltaic and solar parabolic trough), wind generator and geothermal sources to generates

electricity.

Other electricity generation methods include Piezo-electric devices (i.e. power generation from

mechanical strain); Betavoltaics (i.e. power generation from radioactive decay) and electrochemical

cells (Batteries), which are also power generator. Electrochemical cells play important role in portable

and mobile electrical application. Though, it is arguably utilized more as storage systems than generation

systems. (http//en.wikipedia.org)

The quantity of electricity required to fuel the economy is growing every day. Though, there are

many public and private utilities/projects constructed to generate and transmit the electricity to meet

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demand, but many of these projects have caused unpleasant environmental effects such as air/radiation

pollution and the flooding of large areas of land.

2.3 Power supply

Power supply is a device for the conversion of available power of one set of characteristics to

another set of characteristics to meet specified requirements. It makes the load compatible with its power

source. Power supplies belong to the field of power electronics, the use of electronics for the control and

conversion of electrical power. This technology encompasses the effective use of electronics

components, the application of circuit theory and design techniques and the development of analytical

tools toward efficient electronic conversion control and conditioning of electrical power. Overall, the

various power supply topologies to be arranged in an applications “tree” as illustrated in figure 2.2

Basically two types of power supplies are required: Direct Current (DC) power supplies and

Alternating Current (AC) power supplies. The output of dc power supplies is regulated or controllable

DC/AC, whereas the output for ac power supplies could also be DC/AC. The input to these power

supplies can be AC or DC.

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Solar Energy Utilization

Direct Methods Indirect Methods

Thermal Photovoltaic

Bio-Conversion

Water Power Wind Bio-Mass

Ocean Temperature Differences

Figure 2.1: Solar utilization (Sukhatme, 1984)

Figure 2.2: Power Converter Family Tree (Rashid, 1988)

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2.4 Power conversion

Power conversion deals with the process of converting electric power from one form to another.

The power electronic apparatuses performing the power conversion are called power converters. Because

they contain no moving parts, they are often referred to as static power converters. The power

conversion is achieved using power semiconductor devices, which are used as switches. The power

devices used are SCRs (silicon controlled rectifiers, or thyristors), triacs, power transistors, power

MOSFETs, insulated gate bipolar transistors (IGBTs), and MCTs (MOS-controlled thyristors). The

power converters are generally classified as given by Bose (1992):

i. ac-dc converters (phase-controlled converters)

ii. direct ac-ac converters (Cycloconverters)

iii. dc-ac converters (inverters)

iv. dc-dc converters (choppers, buck and boost converters)

2.4.1 AC-DC converters (Rectifiers)

A rectifier is an electrical device that converts alternating current to direct current, a process

known as rectification (the opposite of inverting which converts DC to AC). Rectifiers are used as

components of power supplies and as detectors of radio signals. Rectifiers may be made of solid state

diodes, vacuum tube diodes, mercury arc valves, and other technologies (Bose, 1992).

The primary application of rectifiers is to derive usable DC power from an AC supply. Virtually

all electronics requires a DC supply but mains power is AC so rectifiers find uses inside the power

supplies of virtually all electronic equipment.

2.4.2 AC in, AC out: frequency changer; cycloconverters

A frequency changer or frequency converter is an electronic device that converts

alternating current (AC) of one frequency to alternating current of another frequency. The device may

also change the voltage, i. e. Converters are used to change either the voltage level (i. e. 120V to 240V

AC) or the utility frequency 50Hz and 60Hz power grid. A cycloconverter permits energy to be fed back

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into the utility network without any additional measures. Also, the phase sequence of the output voltage

can be easily reversed by the control system. Cycloconverters have found applications in aircraft systems

and industrial drives. These cycloconverters are suitable for synchronous and induction motor control.

(Bose, 1992)

2.4.3 Dc In, Ac Out: inverter (Electrical)

An inverter is a circuit (made of a sophisticated microprocessor) which convert dc power to ac

power at a desired output voltage or current and frequency. The process of changing D.C to A.C is

known as inversion. A static inverter circuit performs this transformation. The significant is that we are

able to choose the frequency of the alternating signal and for that matter we can vary the frequency at

will. An inverter allows the 12 or 24 volt (battery) DC power available in an automobile or from solar

panels to supply AC power to operate equipment that is normally supplied from a mains power source.

Inverters are used in a wide range of applications, from small switched power supplies for a computer to

large electric utility applications to transport bulk power (Bhat, 1992). Inverters are also used to provide

a source of AC power from photovoltaic solar cells and fuel cell power supplies.

The terms voltage-fed and current-fed are used in connection with inverter circuits to classify it

into type’s i. e. voltage source inverters (VSIs) and current source inverters (CSIs).

A voltage-fed inverter (or Voltage Source Inverter) is one in which the dc input voltage is

essentially constant and independent of the load current drawn. The inverter specifies the load voltage

while the drawn current shape is dictated by the load.

A current-fed inverter (or Current Source Inverter) is one in which the source, hence the load

current is predetermined and the load impedance determines the output voltage. The supply current

cannot change quickly. This is achieved by series dc supply inductance which prevents sudden changes

in current. The load current magnitude is controlled by varying the input dc voltage to the large

inductance; hence inverter response to load changes is slow. Being a current source, the inverter can

survive an output short circuit thereby offering fault ride-through properties.

Voltage control may be required to maintain a fixed output voltage when the dc input voltage

regulation is poor, or to control power to a load. The inverter and its output can be single-phase, three-

phase or multi-phase. Variable output frequency may be required for ac motor speed control where, in

conjunction with voltage or current control, constant motor flux can be maintained.

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Inverter output waveforms are usually rectilinear in nature and as such contain harmonics which

may lead to reduced load efficiency and performance. Load harmonic reduction can be achieved by

filtering (Capacitors and inductors can be used to filter the waveform. Low-pass filters can also be

applied to allow the fundamental component of the waveform to pass to the output while limiting the

passage of the harmonic components.), selected harmonic-reduction chopping or pulse-width

modulation. (Bhat, 1992)

The quality of an inverter output is normally evaluated in terms of its harmonic factor, ρ, distortion

factor, μ, and total harmonic distortion, (thd). These first two factors were defined in terms of the supply

current. For VSI inverters the factors are redefined in terms of the output voltage harmonics as given by

Owen (1996) in equation 2.1 and 2.2

………………..2.1

The distortion factor for an individual harmonic is

…………2.2

The factor Vn /n is used since the harmonic currents produced in an inductive load attenuate with

frequency. The harmonic currents produce unwanted heating and torque oscillations in ac motors,

although such harmonic currents are not a drawback to the power delivered to a resistive heating load or

incandescent lighting load.

Basic inverter circuit designs

In one simple inverter circuit, DC power is connected to a transformer through the centre tap of

the primary winding. A switch is rapidly switched back and forth to allow current to flow back to the DC

source following two alternate paths through one end of the primary winding and then the other. The

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alternation of the direction of current in the primary winding of the transformer produces alternating

current (AC) in the secondary circuit. (http//en.wikipedia.org)

The electromechanical version of the switching device as shown in figure 2.3 includes two

stationary contacts and a spring supported moving contact. The spring holds the movable contact against

one of the stationary contacts and an electromagnet pulls the movable contact to the opposite stationary

contact. The current in the electromagnet is interrupted by the action of the switch so that the switch

continually switches rapidly back and forth. This type of electromechanical inverter switch, called a

vibrator or buzzer, was once used in vacuum tube automobile radios. A similar mechanism has been used

in door bells, buzzers and tattoo guns. As they have become available, transistors and various other types

of semiconductor switches have been incorporated into inverter circuit designs.

Inverter output waveforms

The switch in the simple inverter described above produces a square voltage waveform as

opposed to the sinusoidal waveform that is the usual waveform of an AC power supply. Using Fourier

analysis, periodic waveforms are represented as the sum of an infinite series of sine waves. The sine

wave that has the same frequency as the original waveform is called the fundamental component. The

other sine waves, called harmonics, which are included in the series, have frequencies that are integral

multiples of the fundamental frequency. (http//en.wikipedia.org)

The quality of the inverter output waveform as shown in figure 2.4 can be expressed by using the Fourier

analysis data to calculate the total harmonic distortion (thd). The total harmonic distortion is the square

root of the sum of the squares of the harmonic voltages divided by the fundamental voltage as given by

(http//en.wikipedia.org)

……………2.3

The quality of output waveform that is needed from an inverter depends on the characteristics of the

connected load. Some loads need a nearly perfect sine wave voltage supply in order to work properly.

Other loads may work quite well with a square wave voltage.

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Figure: 2. 3. Simple inverter circuit shown with an electromechanical switch and with a transistor

switch (Owen, 1996).

Figure 2.4: Square waveform with fundamental sine wave component, 3rd harmonic and 5th harmonic

(http//en.wikipedia.org).

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More advanced inverter designs

There are many different power circuit topologies and control strategies used in inverter designs.

Different design approaches are used to address various issues that may be more or less important

depending on the way that the inverter is intended to be used. In more advanced inverter designs various

techniques are used to improve the quality of the sine wave at the transformer input, rather than relying

on the transformer to smooth it. Capacitors and inductors can be used to filter the waveform at the

transformer. Also, it is possible to produce a more sinusoidal wave by having split-rail direct current

inputs at two voltages, or positive and negative inputs with a central ground. By connecting the

transformer input terminals in sequence between the positive rail and ground, the positive rail and the

negative rail, the ground rail and the negative rail, then both to the ground rail a stepped sinusoid is

generated at the transformer input and the current drain on the direct current supply is less choppy. These

methods result in an output that is called a “modified-sine wave”. Modified-sine wave inverters may

cause some loads, such as motors, to operate less efficiently (http//en.wikipedia.org).

Multilevel power inverters use Pulse-Width Modulation (PWM) with high frequency carrier to

more closely approximate a sine function. The quality of an inverter is described by its pulse-rating: a

three-pulse is a very simple arrangement, utilizing only 3-transistors, whereas a more complex 12-pulse

system will give an almost exact sine-wave. In remote areas where a utility generated power is subject to

significant external, distorting influences such as inductive loads or semiconductor-rectifier loads, a 12-

pulse inverter may even offer a better, “cleaner” output than the utility-supplied power grid, and are thus

often used in these areas. Inverters with greater pulse ratings do exist. Simple inverters generate

harmonics which affect the quality of power obtained using them. But PWM inverters eliminate this

means of a sine-wave cancellation using the Fourier series.

DC - to -DC converters

DC-dc converters are used to convert unregulated dc voltage to regulated or variable dc voltage at

the output. They are widely used in switch-mode dc power supplies and in dc motor drive and control

applications (Bose, 1992). They are called chopper-controlled drives. The input voltage source is usually

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a battery or derived from an ac power supply using a diode bridge rectifier. These converters are

generally either hard-switched PWM types or soft-switched resonant-link types. There are several dc-dc

converter topologies, the most common ones being buck converter, boost converter, and buck-boost

converter as shown in Figure 2.5

Figure 2.5: DC-DC converter configurations: (a) buck converter; (b) boost converter; (c) buck-boost

converter. (Bose, 1992)

Buck converter

A buck converter is also called a step-down converter. Its principle of operation is illustrated by referring

to Figure 2.5(a). The IGBT acts as a high-frequency switch. The IGBT is repetitively closed for a time

ton and opened for a time toff. During ton, the supply terminals are connected to the load, and power flows

from supply to the load. During toff, load current flows through the freewheeling diode D1, and the load

voltage is ideally zero. The average output voltage is given by: (Huang, 1995)

V out = DV in …………………………….2.4

Where D is the duty cycle of the switch and is given by D = ton/T, where T is the time for one period. 1/T

is the switching frequency of the power device IGBT.

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Boost converter

A boost converter is also called a step-up converter. Its principle of operation is illustrated by

referring to Figure 2.5(b). This converter is used to produce higher voltage at the load than the supply

voltage. When the power switch is on, the inductor is connected to the dc source and the energy from the

supply is stored in it. When the device is off, the inductor current is forced to flow through the diode and

the load. The induced voltage across the inductor is negative. The inductor adds to the source voltage to

force the inductor current into the load. The output voltage is given by Liu and Lee (1985)

……………..2.5

Thus for variation of D in the range 0 < D < 1, the load voltage Vout will vary in the range Vin < Vout <∞.

Buck-boost converter

A buck-boost converter can be obtained by the cascade connection of the buck and the boost

converter. The steady-state output voltage Vout is given by Philips Semiconductors (2007)

………………….2.6

This allows the output voltage to be higher or lower than the input voltage, based on the duty

cycle D. A typical buck-boost converter topology is shown in Figure 2.5(c). When the power device is

turned on, the input provides energy to the inductor and the diode is reverse biased. When the device is

turned off, the energy stored in the inductor is transferred to the output. No energy is supplied by the

input during this interval. In dc power supplies, the output capacitor is assumed to be very large, which

results in a constant output voltage. In dc drive systems, the chopper is operated in step-down mode

during motoring and in step-up mode during regeneration operation. Philips Semiconductors (2007)

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2.5 Electrical properties of materials in inverters

The following are electrical materials incorporated in inverter circuit design:

i. Power semiconductor

devices

ii. Transformer

iii. Capacitor

iv. Resistor

v. Integrated circuit

vi. Buzzer

vii. Diode

viii. LED

ix. Relay

x. Battery

xi. Heat sink

xii. Vero board

xiii. Metal casing

xiv. Wires

xv. Oscillator

2.5.1 Power semiconductor devices

The modern age of power electronics began with the introduction of thyristors in the late 1950s. Now

there are several types of power devices available for high-power and high-frequency applications. The most

notable power devices are gate turn-off thyristors, power Darlington transistors, power MOSFETs, and

insulated-gate bipolar transistors (IGBTs). Power semiconductor devices are the most important functional

elements in all power conversion applications. The power devices are mainly used as switches to convert

power from one form to another. They are used in motor control systems, uninterrupted power supplies, high-

voltage dc transmission, power supplies, induction heating, and in many other power conversion applications.

(Bose, 1992)

Thyristor and Triac

The thyristor, also called a silicon-controlled rectifier (SCR), is basically a four-layer three-junction

Pnpn device. It has three terminals: anode, cathode, and gate. The device is turned on by applying a short

pulse across the gate and cathode. Once the device turns on, the gate loses its control to turn off the device.

The turn-off is achieved by applying a reverse voltage across the anode and cathode. The thyristor symbol

and its volt-ampere characteristics are shown in Figure 2.6. There are basically two classifications of

thyristors: converter grade and inverter grade (Bose, 1992). The difference between a converter-grade and an

inverter-grade thyristor is the low turn-off time (on the order of a few microseconds) for the latter. The

converter-grade thyristors are slow type and are used in natural commutation (or phase-controlled)

applications. Inverter-grade thyristors are used in forced commutation applications such as dc-dc choppers

and dc-ac inverters. The inverter-grade thyristors are turned off by forcing the current to zero using an

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external commutation circuit. This requires additional commutating components, thus resulting in additional

losses in the inverter.

Thyristors are highly rugged devices in terms of transient currents, di/dt, and dv/dt capability. The

forward voltage drop in thyristors is about 1.5 to 2 V, and even at higher currents of the order of 1000 A, it

seldom exceeds 3 V. While the forward voltage determines the on-state power loss of the device at any given

current, the switching power loss becomes a dominating factor affecting the device junction temperature at

high operating frequencies. Because of this, the maximum switching frequencies possible using thyristors are

limited in comparison with other power devices considered in this section.

Thyristors have I2t withstand capability and can be protected by fuses. The non-repetitive surge current

capability for thyristors is about 10 times their rated root mean square (rms) current. They must be protected

by snubber networks for dv/dt and di/dt effects. If the specified dv/dt is exceeded, thyristors may start

conducting without applying a gate pulse. In dc-to-ac conversion applications it is necessary to use an

antiparallel diode of similar rating across each main thyristor. Thyristors are available up to 6000 V, 3500 A.

A triac is functionally a pair of converter-grade thyristors connected in antiparallel. The triac symbol and

volt-ampere characteristics are shown in Figure 2.7. Because of the integration, the triac has poor reapplied

dv/dt, poor gate current sensitivity at turn-on, and longer turn-off time. Triacs are mainly used in phase

control applications such as in ac regulators for lighting and fan control and in solid-state ac relays (Bose,

1992)

Gate Turn-off Thyristor (GTO)

The GTO is a power switching device that can be turned on by a short pulse of gate current and

turned off by a reverse gate pulse. This reverse gate current amplitude is dependent on the anode current to be

turned off. Hence there is no need for an external commutation circuit to turn it off. Because turn-off is

provided by bypassing carriers directly to the gate circuit, its turn-off time is short, thus giving it more

capability for high frequency operation than thyristors. The GTO symbol and turn-off characteristics are

shown in Figure 2.8. GTOs have the I2t withstand capability and hence can be protected by semiconductor

fuses. For reliable operation of GTOs, the critical aspects are proper design of the gate turn-off circuit and the

snubber circuit (Bose, 1992). A GTO has a poor turn-off current gain of the order of 4 to 5. For example, a

2000A peak current GTO may require as high as 500 A of reverse gate current. Also, a GTO has the tendency

to latch at temperatures above 1250C. GTOs are available up to about 4500 V, 2500 A.

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Figure 2.6: (a) Thyristor symbol and (b) volt-ampere characteristics. (Bose, 1992)

Figure2.7: (a) Triac symbol and (b) volt-ampere characteristics. (Bose, 1992)

Figure 2.8: (a) GTO symbol and (b) turn-off characteristics. (Bose, 1992)

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Reverse-conducting thyristor (RCT) and Asymmetrical silicon-controlled

rectifier (ASCR)

Normally in inverter applications, a diode in anti-parallel is connected to the thyristor for

commutation/freewheeling purposes. In RCTs, the diode is integrated with a fast switching thyristor in a

single silicon chip. Thus, the number of power devices could be reduced. This integration brings forth a

substantial improvement of the static and dynamic characteristics as well as its overall circuit

performance. The RCTs are designed mainly for specific applications such as traction drives. The anti-

parallel diode limits the reverse voltage across the thyristor to 1 to 2V. Also, because of the reverse

recovery behavior of the diodes, the thyristor may see very high reapplied dv/dt when the diode recovers

from its reverse voltage. This necessitates use of large RC snubber networks to suppress voltage

transients. As the range of application of thyristors and diodes extends into higher frequencies, their

reverse recovery charge becomes increasingly important. High reverse recovery charge results in high

power dissipation during switching. The ASCR has a similar forward blocking capability as an inverter-

grade thyristor, but it has a limited reverse blocking (about 20–30V) capability. It has an on-state voltage

drop of about 25% less than an inverter-grade thyristor of a similar rating. The ASCR features a fast

turn-off time; thus it can work at a higher frequency than an SCR. Since the turn-off time is down by a

factor of nearly 2, the size of the commutating components can be halved. Because of this, the switching

losses will also be low. Gate-assisted turn-off techniques are used to even further reduce the turn-off time

of an ASCR. The application of a negative voltage to the gate during turn-off helps to evacuate stored

charge in the device and aids the recovery mechanisms. This will in effect reduce the turn-off time by a

factor of up to 2 over the conventional device. (Bose, 1992)

Power transistor

Power transistors are used in applications ranging from a few to several hundred kilowatts and

switching frequencies up to about 10 kHz. Power transistors used in power conversion applications are

generally NPN type. The power transistor is turned on by supplying sufficient base current, and this base

drive has to be maintained throughout its conduction period. It is turned off by removing the base drive

and making the base voltage slightly negative (within – VBE (max)). The saturation voltage of the device is

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normally 0.5 to 2.5 V and increases as the current increases. Hence the on-state losses increase more than

proportionately with current. The transistor off-state losses are much lower than the on-state losses

because the leakage current of the device is of the order of a few milli-amperes. Because of relatively

larger switching times, the switching loss significantly increases with switching frequency. Power

transistors can block only forward voltages. The reverse peak voltage rating of these devices is as low as

5 to 10 V. Power transistors do not have I2t withstand capability. In other words, they can absorb only

very little energy before breakdown. Therefore, they cannot be protected by semiconductor fuses, and

thus an electronic protection method has to be used. To eliminate high base current requirements,

Darlington configurations are commonly used. They are available in monolithic or in isolated packages.

The basic Darlington configuration is shown schematically in Figure 2.9. The Darlington configuration

presents a specific advantage in that it can considerably increase the current switched by the transistor

for a given base drive. The VCE(sat) for the Darlington is generally more than that of a single transistor of

similar rating with corresponding increase in on-state power loss. During switching, the reverse-biased

collector junction may show hot spot breakdown effects that are specified by reverse-bias safe operating

area (RBSOA) and forward bias safe operating area (FBSOA). Modern devices with highly inter-digited

emitter base geometry force more uniform current distribution and therefore considerably improve

second breakdown effects. Normally, a well-designed switching aid network constrains the device

operation well within the SOAs: (Bose, 1992)

Figure 2.9: A two-stage Darlington transistor with bypass diode. (Bose, 1992)

Power mosfet

Power MOSFETs are marketed by different manufacturers with differences in internal geometry

and with different names such as MegaMOS, HEXFET, SIPMOS, and TMOS. They have unique

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features that make them potentially attractive for switching applications. They are essentially voltage-

driven rather than current-driven devices, unlike bipolar transistors. The gate of a MOSFET is isolated

electrically from the source by a layer of silicon oxide. The gate draws only a minute leakage current of

the order of nano-amperes. Hence the gate drive circuit is simple and power loss in the gate control

circuit is practically negligible. Although in steady state the gate draws virtually no current, this is not so

under transient conditions. The gate-to-source and gate-to-drain capacitances have to be charged

and discharged appropriately to obtain the desired switching speed, and the drive circuit must have a

sufficiently low output impedance to supply the required charging and discharging currents. The circuit

symbol of a power MOSFET is shown in Figure 2.10. Power MOSFETs are majority carrier devices, and

there is no minority carrier storage time. Hence they have exceptionally fast rise and fall times. They are

essentially resistive devices when turned on, while bipolar transistors present a more or less constant

VCE(sat) over the normal operating range. Power dissipation in MOSFETs is Id2RDS(on), and in bipolar it is

ICVCE(sat). At low currents, therefore, a power MOSFET may have a lower conduction loss than a

comparable bipolar device, but at higher currents, the conduction loss will exceed that of bipolar. Also,

the RDS(on) increases with temperature. An important feature of a power MOSFET is the absence of

a secondary breakdown effect, which is present in a bipolar transistor, and as a result, it has an extremely

rugged switching performance. In MOSFETs, RDS(on) increases with temperature, and thus the current is

automatically diverted away from the hotspot. The drain body junction appears as an anti-parallel diode

between source and drain. Thus power MOSFETs will not support voltage in the reverse direction.

(Bose, 1992)

Although this inverse diode is relatively fast, it is slow by comparison with the MOSFET.

Recent devices have the diode recovery time as low as 100 ns. Since MOSFETs cannot be protected by

fuses, an electronic protection technique has to be used. With the advancement in MOS technology,

ruggedized MOSFETs are replacing the conventional MOSFETs. The need to ruggedize power

MOSFETs is related to device reliability. If a MOSFET is operating within its specification range at all

times, its chances for failing catastrophically are minimal. However, if its absolute maximum rating is

exceeded, failure probability increases dramatically. Under actual operating conditions, a MOSFET may

be subjected to transients - either externally from the power bus supplying the circuit or from the circuit

itself due, for example, to inductive kicks going beyond the absolute maximum ratings.

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Such conditions are likely in almost every application, and in most cases are beyond a designer’s control.

Rugged devices are made to be more tolerant for over-voltage transients. Ruggedness is the ability of a

MOSFET to operate in an environment of dynamic electrical stresses as explained by Bose (1992),

without activating any of the parasitic bipolar junction transistors. The rugged device can withstand

higher levels of diode recovery dv/dt and static dv/dt.

Figure 2.10: Power mosfet circuit symbol. (Bose, 1992)

Insulated-gate bipolar transistor (IGBT)

According to Motorola (2008), the IGBT has the high input impedance and high-speed

characteristics of a MOSFET with the conductivity characteristic (low saturation voltage) of a bipolar

transistor. The IGBT is turned on by applying a positive voltage between the gate and emitter and, as in

the MOSFET, it is turned off by making the gate signal zero or slightly negative. The IGBT has a much

lower voltage drop than a MOSFET of similar ratings. The structure of an IGBT is more like a thyristor

and MOSFET. For a given IGBT, there is a critical value of collector current that will cause a large

enough voltage drop to activate the thyristor. Hence, the device manufacturer specifies the peak

allowable collector current that can flow without latch-up occurring. There is also a corresponding gate

source voltage that permits this current to flow that should not be exceeded. Like the power MOSFET,

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the IGBT does not exhibit the secondary breakdown phenomenon common to bipolar transistors.

However, care should be taken not to exceed the maximum power dissipation and specified maximum

junction temperature of the device under all conditions for guaranteed reliable operation. The on-state

voltage of the IGBT is heavily dependent on the gate voltage. To obtain a low on-state voltage, a

sufficiently high gate voltage must be applied.

In general, IGBTs can be classified as punch-through (PT) and non-punch-through (NPT) structures,

as shown in Figure 2.11. In the PT IGBT, an N+ buffer layer is normally introduced between the P+

substrate and the N – epitaxial layer, so that the whole N – drift region is depleted when the device is

blocking the off-state voltage, and the electrical field shape inside the N – drift region is close to a

rectangular shape. Because a shorter N – region can be used in the punch-through IGBT, a better trade-

off between the forward voltage drop and turn-off time can be achieved. PT IGBTs are available up to

about 1200 V. High voltage IGBTs are realized through non-punch- through process. The devices are

built on a N – wafer substrate which serves as the N – base drift region. Experimental NPT IGBTs of up

to about 4 KV have been reported in the literature. NPT IGBTs are more robust than PT IGBTs

particularly under short circuit conditions. But NPT IGBTs have a higher forward voltage drop than the

PT IGBTs. The PT IGBTs cannot be as easily paralleled as MOSFETs. The factors that inhibit current

sharing of parallel-connected IGBTs are (1) on-state current unbalance, caused by VCE(sat) distribution

and main circuit wiring resistance distribution, and (2) current unbalance at turn-on and turn-off, caused

by the switching time difference of the parallel connected devices and circuit wiring inductance

distribution. The NPT IGBTs can be paralleled because of their positive temperature coefficient property

MOS-controlled thyristor (MCT)

The MCT is a new type of power semiconductor device that combines the capabilities of thyristor

voltage and current with MOS gated turn-on and turn-off. It is a high power, high frequency, low

conduction drop and a rugged device, which is more likely to be used in the future for medium and high

power applications. A cross sectional structure of a p-type MCT with its circuit schematic is shown in

Figure 2.12. The MCT has a thyristor type structure with three junctions and PNPN layers between the

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anode and cathode. In a practical MCT, about 100,000 cells similar to the one shown are paralleled to

achieve the desired current rating. MCT is turned on by a negative voltage pulse at the gate with respect

to the anode, and is turned off by a positive voltage pulse. The MCT was announced by the General

Electric R & D Center on November 30, 1988. Harris Semiconductor Corporation has developed two

generations of p-MCTs. Gen-1 p-MCTs are available at 65 A/1000 V and 75A/600V with peak

controllable current of 120 A. Gen-2 p-MCTs are being developed at similar current and voltage ratings,

with much improved turn-on capability and switching speed. The reason for developing p-MCT is the

fact that the current density that can be turned off is 2 or 3 times higher than that of an n-MCT; but n-

MCTs are the ones needed for many practical applications. Motorola (2008)

The advantage of an MCT over-IGBT is its low forward voltage drop. N-type MCTs will be

expected to have a similar forward voltage drop, but with an improved reverse bias safe operating area

and switching speed. MCTs have relatively low switching times and storage time. The MCT is capable

of high current densities and blocking voltages in both directions. Since the power gain of an MCT is

extremely high, it could be driven directly from logic gates. An MCT has high di/dt (of the order of 2500

A/µs) and high dv/dt (of the order of 20,000 V/µs) capability. The MCT, because of its superior

characteristics, shows a tremendous possibility for applications such as motor drives, uninterrupted

power supplies, static VAR compensators, and high power active power line conditioners. The current

and future power semiconductor devices developmental direction is shown in Figure 13. High

temperature operation capability and low forward voltage drop operation can be obtained if silicon is

replaced by silicon carbide material for producing power devices. Motorola (2008)

The silicon carbide has a higher band gap than silicon. Hence higher breakdown voltage devices

could be developed. Silicon carbide devices have excellent switching characteristics and stable blocking

voltages at higher temperatures. But the silicon carbide devices are still in the very early stages of

development.

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Figure 2.11: Non-punch-through IGBT, (b) Punch through IGBT, (c) IGBT equivalent circuit. (Motorola, 2008)

Figure 2.12: Circuit schematic for P-MCT Figure 2.13: Current and future power semiconductor devices development direction (Motorola, 2008)

(Motorola, 2008)

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2.5.2 Transformer

A transformer is an electro-static device that has ability and capability to step up or step down the

input voltage supplied to it. The output voltage of the transformer is base on the circuit voltage

requirement, it convert Alternating Current (A.C) to Direct Current (D.C). The transformer is wound in

two directions such as;

a) Primary Winding: This is the input voltage (A.C) of the transformer which determined

the output voltage (D.C).

b) Secondary Winding: This is the output voltage (D.C) of a transformer that is directed to

the load. The output voltage (D.C) varies due to different circuit, different voltage and

different operation.

Figure 2.13: Transformer diagram (DBTI, 2005)

The power and efficiency of a transformer depends on the number of turns wound on both the

primary and secondary winding and the lamination used to reduced the core losses. Other types of

transformer include Auto transformer, Current transformer, Potential transformer, Core type

transformer, Shell type transformer. To know the amount of flux produced by primary passes through

the secondary, the electromotive force (E.M.F) produced in each turn is the same as primary and

secondary hence N1 and N2 being the number of turns in primary and secondary respectively as given by

DBTI training manual:

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Total E.M.F in secondary

Total E.M.F in primary

N2 x E.M.F /turns

N1 x E.M.F /turns ………………………….2.7

E2 = N2 = I1 E1 N1 I2. ………………………….2.8

OR

V2 = N2 = I1 V1 N1 I2 ………………………….2.9

Efficiency of a Transformer: This is losses which occur in a transformer on – load and it can be

divided into groups as given by DBTI (2005)

a. Copper Losses: It is divided into two such as: primary losses = I2R, secondary losses = I2 R2

b. Core Losses: This is due to eddy current or hysteresis since the maximum value

of the flux in the transformer does not vary by more than about 2 percent between

no – load and full – load. It is usually assumed that the core loss is constant at all

loads.

Hence PC = total core losses

Total loss in transformer = PC + I2R + I2R2

Efficiency = Output power Input power

Output power = V X I X P.F

Input power = output power + total losses

= V X I X P.F + I2 R, + I2 R2.

Efficiency = V X I X P.F X 100% V X I X P.F + I2 R + I2R2 ………………2.10

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2.5.3 Capacitor ( )

This is an electronics device that is used to store electric charges in an electrical circuit. A

capacitor is used with a resistor in a timing circuit. It can also be used as a filter, smoothing of

alternating current (A.C) supply i. e. to block DC signals but pass AC signals. The unit of capacitor is

micro- Faraday’s and the amount of change store by a capacitor is given by DBTI (2005)

Q = C – V ……..………………………………………………….2.11

Where, Q = Amount of charge in coulomb ©

V = Voltage in the circuit in volt (V)

C = Capacitance in Faraday’s (F)

Capacitor is use in store energy. E = Q V

Where, E = Energy store in joules (J)

2.5.4 Resistor: ( )

This is an electronics component that is used to restrict the flow of current electrical circuit, for

example to limit the current passing through a LED. A resistor is used with a capacitor in a timing

circuit. The unit of resistor is ohms (Ω). (DBTI, 2005)

2.5.5 Integrated circuit (IC)

This is an electronic device that has a reduced the size, weight and power requirement of today

electronic gadget and replace transistor as transistor replaced vacuum tubes. It contains microscopically

small electronic components such as: Diodes, Transistors, Resistors and Capacitors. It is classified into

two such as digital and linear integrated circuit (IC). Digital IC is used in computer, calculators and

digital clock as well as many other digital devices. Linear IC is used in audio amplifiers, voltage

regulators, operational amplifiers and radio frequency circuit and most of linear IC is low power devices.

(Wojslawowicz, 2005)

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2.5.6 Buzzer

This is an electronics device or a transducer which converts electrical energy to sound. It can

be used to indicate when there is power failure and power supply. (Wojslawowicz, 2005)

2.5.7 Diode

This is an electronic device which only allows current to flow in one direction. It can be used for

the conversion of alternating current (A.C) to direct current (D.C). It is made of semi-conductor material

(Silicon). (Wojslawowicz, 2005)

2.5.8 Light emitting diode (LED)

This is an electrical/electronic transducer which converts electrical energy to light. It is used to

indicate whether a circuit is energised or not (i.e. If current is present in the circuit) and is connected to

group of resistor in series to divide the voltage passing across to the LED. (Mohan and Undeland, 1995)

2.5.9 Relay:

This is an electronic component that is working with the principle of electromagnetic induction

and as the ability and capability of making and breaking of a contact. It has normally opened (NO) and

normally closes (NC) contacts. (DBTI, 2005)

2.5.10 Battery:

A battery is a device in which chemical energy is directly converted to electrical energy. It

consists of one or more voltaic cells, each of which comprises two half-cells connected in series by the

conductive electrolyte. A battery consists of one or more voltaic cells in series. Each cell has a positive

electrode (cathode), and a negative electrode (anode). These do not touch each other but are immersed in

a solid or liquid electrolyte. In a practical cell the materials are enclosed in a container, and a separator

between the electrodes prevents them from touching one another. Batteries are usually divided into two

broad classes:

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i. Primary batteries irreversibly transform chemical energy to electrical energy. Once the initial

supply of reactants is exhausted, energy cannot be readily restored to the battery by electrical

means.

ii. Secondary batteries can be recharged, that is, have their chemical reactions reversed by

supplying electrical energy to the cell, restoring their original composition.

The types of secondary batteries that can be used for inverters are;

a. Car (Very short life) – not recommended

b. Marine (Short Life) – the bare minimum

c. Golf cart (5 to 8 years)

d. Deep cycle L16s (7 to 10 years)

e. Industrial (10 to 30 years)

The years stated are achievable only if the battery is not discharged below 50% DOD of cycle and

with proper maintenance. (www.outbackpower.com)

2.5.11 Heat sink

This is a device that is made up of aluminium which is use to absorbed heat generated by

semiconductor devices i. e. transistors. It has high heat absorption ability due to the material it’s

made of. (Harris Semiconductor, 2000)

2.5.12 Vero board

This is an electronics panel or platform that is used to connect electronic components together to

make up electrical/electronic system. (DBTI, 2005)

2.5.13 Wire: ( )

This is an electrical material, which pass current very easily from one part of a circuit to another.

(DBTI, 2005)

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2.5.14 Metal casing

This is a material that stands as a body of the work (i.e. Material that cover all the component

after it has been coupled or connected together). It resists external reaction on the components. (DBTI,

2005)

2.5.15 Oscillator

This is a component which converts direct current into high frequency alternating current.

Different IC used as oscillators are 555Timer, CD4047, MM5369, and SG3224 (Harris Semiconductor,

2000). Oscillators are circuits that produce specific, periodic waveforms such as square, triangular, saw

tooth, and sinusoidal. They generally use some form of active device, lamp, or crystal, surrounded by

passive devices such as resistors, capacitors, and inductors, to generate the output.

2.6 Domestic electric power consumption

Consumption of electrical power varies from one place to another. PHCN, (2009) stated that the

average and ideal electrical power consumed per house within the Akure community is given as follows:

i. Average electrical power consumed per house in a day is 6.5 kilowatts

ii. Ideal electrical power consumption per house in a day is about 10 kilowatts

iii. Average electrical power consumed per house in a month is 200 kilowatts

iv. Ideal electrical power consumption per house in a month is about 300 kilowatts

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CHAPTER THREE

3.0 METHODOLOGY

3.1 Description and working principles of 2KW Inverter

The 2KW inverter designed for farm household is an integrated version of current and voltage-

fed static circuitry* made of sophisticated microprocessors (such as FETS, oscillators etc) which

performs the transformation of input DC power to AC power with transformer as integral of the

system at a desired operating output voltage of 220 – 240V and 50Hz frequency. The significant of

this is that we are able to choose the frequency of the alternating signal and for that matter we can

vary the frequency at will. This inverter allows only the use of 12 volt (battery) DC power available in

an automobile/marine battery/fuel cells/solar panels to supply AC power to operate equipment that is

normally supplied from a mains power source.

The methodology used to achieve the objectives focused on the design of transformer as the

main integral part of the inverter, while the design and selection of other components were based on

their electrical properties and affordability. The inverter was designed as a 12-pulse inverter i.e.

consists of 12 IRFP 260N FETS transistors to smoothing and supply electric power

The sinusoidal waveform of the load harmonic modulation was achieved by filtering i. e.

Capacitors and inductors were used to filter the waveform. Low-pass filters were also to smoothing

further the waveform of the inverter thereby making the pulse-width modulation of the inverter

similar to the sinusoidal waveform of PHCN power grid.

The 2KW power inverter for farm household operates on the principle of Inversion of power

supply, in the sense that when there is power supply (A.C) from PHCN it will charge the battery and

at the same time passing current to the appliances connected to it. Immediately there is failure in the

power supply it will continue the power supply, feeding from the D.C source i. e. Battery, within

micro-second without affecting the operation of the appliance connected to it. It can also work

independent of the grid.

*Details about Current/Voltage fed Inverter is on page 8

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3.2 Design Consideration for 2KW Inverter

The design, selection of electrical materials and development of this inverter device were

based on the following criteria:

a. Design of 2181Watts transformer (Note that the little wattage increased is meant to

compensate for power loss within the circuit)

b. Availability i.e. locally available, especially of being easily accessible or obtainable

c. Durability i.e. the ability of the materials to work for long period of time without

damaging its thermal and electrical properties.

d. Cost affordability

e. Thermal properties of the material

f. Electrical properties of the material

The details of the designed and selected materials for the 2,000Watts are shown in Table 3.2.

Inverter rating is based on its pulse i.e. pulse width modulation. To achieve this, IGBT is the most

suitable because it has the high input impedance and high-speed characteristics of a MOSFET with

the conductivity characteristic (low saturation voltage) of a bipolar transistor. IGBT is costly and is

not readily available in the market. This necessitates me to choose the closest material i. e.

MOSFETS IRFP 260N in the terms of cost and electrical properties for the design of the inverter as

shown in figure 3.1 and Appendix C.

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3.3 Design Calculation for 2KW Inverter

The summary details calculation of transformer design, the electrical characteristics of the Power

Mosfet - IRFP 260N to be used in 2KW inverter are shown in table 3.1. The full details and electrical

details of the battery are on appendix B and C

Table 3.1: The details of items designed

a. Transformer

OUTPUT POWER

(Watts)

Number of Turns

Section of the Coil

Area

(mm2)

Voltage

(Volts)

2,181

N1 ≈ 19

N 2 ≈ 10

S1 = 1.14

S2 = 27.5

V1 = 240

V2 = 12

b. Power Mosfet - IRFP 260N

Voltage Current

200Volts 50Ampere

c. Battery, (Lead –acid accumulator)

Voltage Ampere Hour Power

12Vdc 200AH 2400VAdc

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Figure 3.1: Schematic Diagram of 2KW Inverter Circuit

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3.4 Material selection for the Inverter components

The criteria of selecting electrical materials used in the development of 2KW inverter device were

outlined in the table below:

Table 3.2: The electrical materials selected for the development of 2,000Watts Inverter

S/N COMPONENTS CRITERIA FOR

SELECTION

MATERIAL

SELECTED

REASON FOR

SELECTION

i. Transformer

It should be able to

step up voltage and

meet 2,000Watts

output

Step up transformer

from 12V – 260V

Step up of input voltage

to High voltage and

ability to supply the

needed power output, i. e.

2,000 Wattage

ii. FETS Transistor Fast switching IRFP 260N

High amplification of

current and cost

affordability

iii. Capacitor To deal with power 10 V, 4700 UF mica

To store charges

temporarily and

smoothing the current.

iv. Resistor High current and

thermal resistance

10KΩ, 100Ω, 39Ω,

50KΩ of variable

resistor

To reduced the flowing of

current across the circuit

and serves as voltage

divider.

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v. Battery

To be able to

charge and

discharge for long

duration of time

Lead-acid

accumulator Cost affordability

vi. Diode Rectification of

current 5339

To convert from A.C to

D.C

vii. LED To serve as

indicator 3 – 9 V LED

To indicate present of

electrical current in the

circuit

viii. Buzzer To serve as

indicator SFM – 27

To produce sound when

current enter and out of

the circuit.

ix. Heat sink Heat dissipation Thick aluminium Good conductor of heat.

x.

Wire

To pass current

very easily from

one part of a circuit

to another.

0.5m2 & 2.5mm2 wire

Passage of current from

one part of a circuit to

another.

xi. Metal casing

To serve as housing

and packaging

material for all

components of

inverter

SWG – 18 galvanized

plate.

High resistance to

corrosion and easy

beautification.

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3.5 Assembly of Components

The assembly of inverter components was done in the electrical workshop of Don Bosco

Technical institute of Electrical Engineering and Maintenance, Akure. The following were the steps

taken to ensure proper installation of the Inverter:

i. Construction was all done point to point on the Vero-board.

ii. The transformer is relatively large and heavily laminated. The E and I sheets alternate

direction to minimize electromagnetic flux loss. There are insulating layers between each of

the primary and secondary windings. The number of turns in the output winding was

determined based on its measured resistance, core diameter, and the wire gauge table. (also

see the appendix II for the transformer calculation)

iii. The FETs transistor were marked IRFP 260N is a close match of high power amplifier

switch 200V, 50A, 0.04Ω, 300W. The transistors are mounted on heat sinks which form the

sides of the case.

iv. Other components such as capacitors, resistors, integrated circuit, relays, diodes and

chokes, where all connected on the Vero-board accordingly to the way they were shown on

the circuit diagram.

v. The assembled components were then placed in the metal casing as it is being shown in

plate 3.1

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Plate 3.1: Assembled components of Inverter circuit

Plate 3.2: The connection of Inverter to 12V, 200AH battery

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3.6 Evaluation of the Device

The following tests were carried out on newly constructed power inverter was done in the

electrical workshop of Don Bosco Technical institute of Electrical Engineering and Maintenance,

Akure.

i. Continuity test

ii. Test without load

iii. Test with compressive load

iv. Test with non-compressive load

Load testing is carried to verify that the inverter when connected with battery can deliver its

specified power when needed and to size with require battery.

a. Continuity Test:

This test was carried out to determine that every continuity wire on the device is functioning

and they are in proper working condition so that when current is supply to the circuit, it will be

able to carry out necessary operation and prevent short circuit.

b. Test without Load:

This test was carried out on a newly constructed 2,000Watts Power Inverter when it has been

connected to the fully charged battery of 12V, 200Amp Hour. This enable me to know if the

input and the output voltages are functioning as it was expected of it and also check the

temperature of the heat sink in the circuit. The battery monitoring device was attached to the

battery to determine the discharge rate of the battery without load and current consume by the

inverter when it is idling.

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c. Test with non-compressive Load

This test was carried on newly constructed Inverter. A non-compressive load of 1,916Watts

were applied to the inverter output. Table 3.3 shows the electrical power of the non-

compressive loads applied and running test period. The battery monitoring device was

attached to the battery to determine the discharge rate of the battery with efficiency of the

inverter when connected to the non-compressive applied load. Non-compressive load requires

no extra electrical power /current /torque for starting up or operation.

d. Test with compressive load

This test was carried on newly constructed Inverter. A non-compressive load of 1,455Watts

were applied to the inverter output. Table 3.4 shows the electrical power of the compressive

loads applied and running test period. The battery monitoring device was attached to the

battery to determine the discharge rate of the battery with efficiency of the inverter when

connected to the compressive applied load. Compressive loads require 5 times of their

electrical power /current /torque for starting up or operation.

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Table 3.3: The electrical power of the non-compressive loads applied and running test period

Table 3.4: The electrical power of the compressive loads applied and running test period

Home Appliance

Type

Power rating (Watts)

Quantity

Appliance Running Test-time (Hours)

Energy consumed

per appliance (Watts)

Florescent lamp

Energy saving lamp

20 1 4 80

Lamp

40 1 4 160 60 1 4 240 100 1 4 400 200 1 4 800

14ii TV colour

59 1 4 236

Total energy consumed 1,916

Home

Appliance

Type Power rating

(Watts) Quantity

Appliance

Running

Test-time

(Hours)

Energy

consumed

per

appliance

(Watts)

Fan Table 50 1 3 150

Standing 135 1 3 405

Water

Pump

No

automatic 300 1 3 900

Total energy consumed 1455

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Table 3.5: Bill of Materials

PARTS QUANTITY DESCRIPTION

UNIT

COST

N : K

TOTAL

COST

N : K

i. 1 Step-up transformer (12V-

260V) 2,000Watts output. 15,500 15,500

ii. 12 FETS Transistors (IRFP 260N) 460 5,520

iii. 1 Heat sink 700 700

iv. 1 Metal casing 4,500 4,500

v. 10 1N400 Silicon Diode 50 500

vi. 10 Capacitors 50 500

vii. 20 Resistors 50 1,000

viii. 2 Integrated circuit (I C) 450 900

ix. 1 roll Soldering lead 950 950

x. 1 Vero board 450 450

xi. 6 LED 50 300

xii. 1 Buzzer 150 150

xiii. 2 yards Wire 100 200

xiv. 1 Plug 180 180

xv. 2 Crocodile clip 50 100

xvi. 1 Battery (Dry cell) 2,500

xvii. Transportation 3,500

TOTAL 37,450

Research base on the internet work and printing of the work cost N3, 500.00.

Workmanship (Cost of soldering and coupling of materials) = N 4,500.00

Total cost of production = N (37,450+ 3,500 + 4,500)

= N45, 450

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CHAPTER FOUR

4.0 RESULTS AND DISCUSSION

The results of the evaluation carried out on the inverter such as continuity test; test without load;

test with compressive load; and test with non-compressive load are given as follows:

4.1 Continuity Test:

The continuity test was done to ensure that there is no leakage of current and short circuit on the

circuitry. I also, tested the device for continuity range. The circuitry was found to be functioning.

When carry out this test, multi-meter instrument was used.

4.2 Test without Load

This test was carried out to determine the power consumption rate or the idling power of

the inverter when connected to the fully charged battery of 12V, 200Amp Hour and is not on any

applied load. The data generated on table 4.1 as shown in appendix D is illustrated in the figure 4.1:

DOD against test-time without load. The horizontal axis measures the test-time in hours. The

vertical axis gives the depth of discharge in percentage (%) as it is been monitored by battery

monitoring device attached to the battery. The equation of figure 4.1 is given as:

2.1028.1 +−= xy .............4.1

This shows that for the 4hours test period of using the inverter without applied load, 5% of

the actual total battery charges was consumed i.e. 120VAdc

%95;4 == yhoursx

It can be deduced from the above analysis that the inverter uses averagely 30VAdc of battery

energy per hour and it will take the inverter 40hours to discharge the battery to 50% DOD (the

acceptable level) of continuous use without applied load. Conversely, as the test-time increases, the

battery energy reservoir will continue to decrease.

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y = -1.8x + 102.2

R2 = 0.9878

0

10

20

30

40

50

60

70

80

90

100

110

0 1 2 3 4

DE

PTH

OF

DIS

CH

AR

GE

(%)

TIME (hours)

Figure 4.1: DOD AGAINST TEST-TIME WITHOUT LOAD

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4.3 Test with non-compressive Load

This test was carried out to determine the effect of non-compressive loads has on the fully

charged battery of 12V, 200Amp Hour when is connected to the inverter. The data generated on table 4.2

as shown in appendix D is illustrated in the figure 4.2: DOD against test-time on non-compressive load.

The horizontal axis measures the test-time in hours. The vertical axis gives the depth of discharge in

percentage (%) as it is been monitored by battery monitoring device attached to the battery. The equation

of the figure 4.2 is given as:

4.1124.14 +−= xy .............4.2

This shows that for the 4hours test period of using the inverter without applied load, 54.8% of the actual

total battery charges was consumed i.e. 1,315.2VAdc

%2.45;4 == yhoursx

It can be deduced from the above analysis that the non-compressive loads consumed more than the

average of battery charges of battery energy within 4hours of test period. It consumed averagely

328.75VAdc of battery energy per hour of use with non-compressive loads. This shows that the battery

can only be used for 3hours period against the non-compressive loads, to keep the depth of discharge

within acceptable level of 50%. There is a little difference from the model equation and the result on the

table 4.2, this may due to the internal friction/reaction of the lead-acid battery components which we did

not account for during design analysis or test of the device.

The electrical property of the inverter was measured when connected to applied loads with Clamp-on

meter. The results obtained on table 4.3 were tabulated against designed values as shown in appendix D.

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y = -14.4x + 112.4R² = 0.994

0

10

20

30

40

50

60

70

80

90

100

110

0 1 2 3 4

DE

PTH

OF

DIS

CH

AR

GE

(%)

TIME (hours)

Figure 4.2: DOD AGAINST TEST-TIME ON NON-COMPRESSIVE LOAD

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4.4 Test with compressive Load

This test was carried out to determine the effect of compressive loads has on the fully charged

battery of 12V, 200Amp Hour when is connected to the inverter. The data generated on table 4.4 as

shown in appendix D is illustrated in the figure 4.3: DOD against test-time on compressive load. The

horizontal axis measures the test-time in hours. The vertical axis gives the depth of discharge in

percentage (%) as it is been monitored by battery monitoring device attached to the battery. The equation

of the figure 4.3 is given as:

1298.21 +−= xy .............4.3

This shows that for the 3hours test period of using the inverter without applied load, 63.6% of the actual

total battery charges was consumed i.e. 1,526.4VAdc that is

%4.36;3 == yhoursx

There is a great disparity of 16% of energy reservoir between the model equation results and the obtained

results on the table 4.3. This further explained that the lead-acid battery components deteriorate

internally faster when is used as energy reservoir for inverter to power compressive load. We may say

that a deep discharge of the lead-acid battery is not properly suitable to be used as energy reservoir to

power farm household.

It can be deduced from the above analysis that the compressive loads consumed more battery energy

than the non-compressive loads within 3hours of test period. It consumed averagely 508.8VAdc of

battery energy per hour of use compare with non-compressive loads of 328.75VAdc. This shows that the

power factor of compressive loads is greater and it can only be powered for 2hours period to keep the

depth of discharge within acceptable level of 50%.

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y = -21.8x + 129R² = 0.999

0

10

20

30

40

50

60

70

80

90

100

110

0 1 2 3

DE

PTH

OF

DIS

CH

AR

GE

(%)

TIME (hours)

Figure 4.3: DOD AGAINST TEST-TIME ON COMPRESSIVE LOAD

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CHAPTER FIVE

5.0 Conclusion and Recommendation

5.1 Conclusion

In conclusion, the inverter was designed, developed and tested. It is a 12-pulse inverter i.e.

consists of 12 IRFP 260N FETS transistors to supply electric power similar to the power grid of

sinusoidal waveform and 2,024Watts transformer power output as against 2,181Watts designed for. It

was tested as independent unit of power supply with forgo lead-acid battery product of 12V,

200Amperes Hour against idling; non-compressive and compressive loads. From the graphic analyses, it

shows that the inverter consumed little battery energy when no load is applied; while on non-

compressive loads, it consumed 54.8% of the total battery charges within 4hours of test period. 63.6% of

the battery energy was consumed when on compressive loads for 3hours test period. This shows that the

power factor of compressive loads is greater and the use of the lead-acid battery to supply energy to the

inverter to power compressive load will drain maximum current output from it within the test period.

The disparity in the percentage of energy reservoir between the model equation results and the obtained

results on the tables 4.2 and 4.3 with their graphical analyses further explained that the lead-acid battery

components are deteriorating internally when is used as energy reservoir for inverter to power non-

compressive and compressive loads.

We may conclude that lead-acid battery is unreliable to be used as energy reservoir to power farm

household on a continuous basis and repeated deep discharges of the battery will result in capacity loss

and ultimately in premature failure.

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The 2,000Watts inverter constructed is sensitive to the low voltage power supply from PHCN and

it will shut down the entire system to prevent it from malfunctioning when it is used as battery charger.

The cost of production was N45, 450. The power device system was tested and found out to be

functioning very well with 93% power efficiency.

5.2 Recommendation

Based on the test carried out on the inverter, the following are recommended:

i. That further work should be carried out on the inverter by testing it on deep cycle battery i.e. it is

specially designed to withstand greater degree of discharging and much less susceptible to

degradation than lead acid battery.

ii. The power device system was tested and found out to be functioning very well but further work

will make it more efficient and reliable to be used in the farm households and settlements.

iii. Sizing the inverter with battery should be based on the applied load power and battery capacity

iv. If you are not around put off the inverter to prevent danger. This is because failure can occur in

the change-over when Power Holding Company of Nigeria (PHCN) supply comes.

v. The power of the inverter can be increased by increasing the wattage of the transformer to power

heavy machines on the farm and meet future needs.

vi. Keep away from the children because the voltage produce is lethal and can kill.

vii. If the inverter is going to be used more than the tested period, it is advisable to increase the

battery capacity to two or more by connecting them in parallel.

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REFERENCES

Bhat A.K.S. (1992): “Fixed frequency PWM series-parallel resonant converter,” IEEE Trans. Industry Applications, vol. 28, no. 5, pp. 1002–1009

Bird B.M. and King K.G. (1984): An Introduction to Power Electronics, New York: Wiley-Interscience

Bose B.K. (1992): Modern Power Electronics: Evaluation, Technology, and Applications, New York: IEEE Press

DBTI (Don Bosco Technical Institute Training manual) (2005): Volume 3, pp. 85-110. Don Bosco Press

Harris Semiconductor (2000), User’s Guide of MOS Controlled Thyristor, CRC Press LLC

http://en.wikipedia.org/wiki/Inverter (electrical)

http://www.outbackpower.com

Huang A.Q. (1995): Recent Developments of Power Semiconductor Devices, VPEC Seminar Proceedings, pp. 1–9

Liu K. H., Oruganti R., and Lee F.C. (1985): “Resonant Switches—Topologies and Characteristics,” IEEE Power Electronics Specialists Conference Record, pp. 106–116.

Mohan N. and Undeland T. (1995): Power Electronics: Converters, Applications, and Design, New York: John Wiley & Sons

Motorola, Linear/Switchmode Voltage Regulator Handbook, 2008.

Olaitan, S., and Omoniyi L. (2007): Design and construction of 1000Watts automatic uninterruptible power supply for household electricity supply. Don Bosco technical college, Akure

Owen, E. L. (January/February 1996). "Origins of the Inverter". IEEE Industry Applications Magazine: History Department 2 (1): pp64-66.

Philips Semiconductors, Power Semiconductor Applications, 2007.

PHCN (Power Holding Company of Nigeria), 2008. Marketing Department, Akure Office

Rashid M. H. (1988): Power Electronics, Circuits, Devices and Applications, Englewood Cliffs, N.J.: Prentice-Hall

Sukhatme, S. P. (1984): Principles of Thermal Collection and Storage. India, TATA McGraw-Hill publishing company limited, pp. 2-15

Wojslawowicz, J. (Jan. 1988): “Ruggedized transistors emerging as power MOSFET standard-bearers,” Power Technics Magazine, pp. 29–32

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APPENDIX A

Definition of Terms

ac: Alternating current

Ac: Alternating current

Commutation: Process of transferring the current from one power device to another.

DBTI: Don Bosco Technical Institute

dc: Direct current

di/dt limit: Maximum allowed rate of change of current through a device. If this limit is exceeded,

the device may not be guaranteed to work reliably.

DOD: depth of discharge

Duty cycle: Ratio of the on-time of a switch to the switching period.

dv/dt: Rate of change of voltage withstand capability without spurious turn-on of the device.

Forward voltage: The voltage across the device when the anode is positive with respect to the

cathode.

Full-wave control: Both the positive and negative half cycle of the waveforms are controlled.

I2t: Represents available thermal energy resulting from current flow.

IGBT: Insulated-gate bipolar transistor.

Phase-controlled converter: Converter in which the power devices are turned off at the natural

crossing of zero voltage in ac to dc conversion applications.

Reverse voltage: The voltage across the device when the anode is negative with respect to the

cathode.

SCR: Silicon-controlled rectifier.

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APPENDIX B

TRANSFORMER ANALYSIS

Design Calculation Analysis of 2000Watts Transformer.

A transformer to be constructed has the following data which are:

K.F = 1.05, K = 1, γ = 0.90, β = 1.1, F = 50Hz, V1= 240v, V2 = 12v, δ1 = 8A/mm2, δ2 = 8A/mm2, P1 =?, P2 =?, S1=?, S2

=?, N1 =?, N2 =?, θ1 = ?, θ2 = ?,.

S.G = 70 X 70mm for lamination, and S.G = 70 X 70mm for thermoplastic.

Where, S.G = length and width of the lamination

and thermoplastic,

K = coefficient factor,

γ = efficiency,

β = induction of the coil,

F = frequency

V1 & V2= input & output voltage

δ1 & δ2 = density

P1 & P2= power

N1 & N2 = number of turns

I1 & I2 = input & output current

S1 & S2 = section of the coil

θ1& θ2 = diameter of the coil.

TRANSFORMER 2000 WATTS

70

70

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POWER CALCULATION S.G = 70 X 70mm = 4,900mm2 P1 = Sg

P1 =

2

K x K.F x 100

70 X 70

P1 =

2

1 x 1.05 x 100

4900 2

105

P1 = (46.7)2

P1 = 2,181W

P1 = P2 in (VA) γ

P2 = P1 x γ (VA)

P2 = 2181 x 0.9

P2 = 1963VA

E.M.F. Equation of a transformer & Number of turns

Let N1 = Number of turns in primary side

N2 = Number of turns in secondary side

Φm = maximum flux in core in Webers is

= Bm X A

F = frequency of a.c. input in Hz

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Cycle Φm T/4.f

Time T =1/f Flux increases from its zero value to maximum value Φm in one quarter of the cycle i.e. in ¼ f second.

Average rate of change of flux =

: Form factor is given as = 1.11

:

r.m.s value of e.m.f/turn = 1.11 X 4f Φm = 4.44 f Φm

Calculation of voltage per turn

e = 4.44 X f X β X s.g X 10-6

= 4.44 X 50 X 1.1 X 4900 X 10-6

= 1.1966 v/t

N1 = V1/e

= 240/1.1966

= 201 turns.

N2 = V2/e

Φm

1/4f

=4 f Φm Wb/s or volt

Now, rate of change of flux per turn means induced e.m.f in volts.

: Average e.m.f. /turn = 4f Φm volt

If flux Φ varies sinusoidally, then r.m.s. value of induced e.m.f. is obtained by multiplying the average

value with form factor.

r.m.s. values Average values

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= 12/1.1966

= 10 turns

PRACTICAL ASPECT OF DETERMINING NUMBER OF TURNS

N’1 = N1 - N1 X 2.5

100

= 201 –

N’2 = N2 + N2 X 2.5

100

= 10 +

201 X 2.5

100

= 201 -5.025

≈ 196 turns.

I1 = P1 =

10 X 2.5 100

= 10 + 0.25

≈ 10 turns.

2,181 , I1 = 2,181

V1 220 240

I1 = 9.91A , I1 = 9.1A

I2 = P2 I2 =

V2 12

I2 = 160A

1963

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CALCULATION OF THE COIL SECTION

Section S1 = I1 = (mm2)

δ

S1 = I1 = (mm2); S2 = I2 = (mm2)

δ1 δ2

S1 = 9.1

8

S1 = 1.14mm2

S2 = I2

S2

S2 =

θ1 = 2

220

8

S2 = 27.5mm2

DIAMETER OF THE COIL CALCULATION

Where S1 = 2

S1 Π

S1= 2

S1

3.142

1.13

3.142

S1 0.6mm

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Where S2 = 2

S2 = 2

S2

3.142

27.5

3.142

S2 = 3mm

I1 =

P1 V1

I1 = 2,181WATTS

Summary of the Inverter design

a. Transformer

OUTPUT POWER (Watts)

Number of Turns Section of the Coil

Area (mm2)

Voltage (Volts)

2,181

N1 ≈ 19 N 2 ≈ 10

S1 = 1.14 S2 = 27.5

V1 = 240 V2 = 12

c. Battery, (Lead –acid accumulator) forgo Product

Voltage Ampere Hour Power

12Vdc 200AH 2400VAdc

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APPENDIX C

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APPENDIX D

Table 4.1: The result of idling load against DOD

Table 4.2: The result of non-compressive load against DOD

Depth of

Discharge

DOD (%) y

100 81 69 55 41

Time (Hour) x 0 1 2 3 4

Table 4.4: The result of compressive load against DOD

Depth of

Discharge

DOD (%)

100 73 45 15

Time (Hour) 0 1 2 3

Depth of

Discharge

DOD (%) Y

100 99 97 95 93

Time (Hour) X 0 1 2 3 4

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Table 4.3: Values of electrical properties of 2,000Watts Inverter

Electrical properties

Designed

values

Measured values

Nominal AC output Voltage

(V) 220Vac 220Vac

Ac operating voltage Range

(V) 220 – 240Vac 220 – 240Vac

Nominal AC Frequency 50Hz 49.5Hz

Maximum AC output Current

(I) 9.91 9.2Aac

Maximum AC output Power

(IV) 2,181Wac ≈2,024Wac

Efficiency (%) 93%