Design and Construction of 2KW Solar Panel Inverter

DESIGN AND CONSTRUCTION OF 2KW SOLAR
PANEL INVERTER
BY
OMOSANYA, HAFEEZ ABOLADE
Matric NO: 10/ENG04/037
A FINAL YEAR PROJECT REPORT
SUBMITTED TO
THE DEPARTMENT OF ELECTRICAL/ ELECTRONIC AND
COMPUTER ENGINEERING, AFE BABALOLA UNIVERSITY,
ADO-EKITI.
IN PARTIAL FUFILLMENT OF THE REQUIREMENTS FOR
THE AWARD OF BACHELOR OF ENGINEERING (B.ENG)
DEGREE IN ELECTRICAL AND ELECTRONIC
ENGINEERING
JUNE, 2015.

i
CERTIFICATION
This is to certify that this report was prepared and presented by OMOSANYA, HAFEEZ
ABOLADE with student matriculation number 10/ENG04/037 in the Department of
Electrical/Electronic and Computer Engineering, College of Engineering, AfeBabalola University,
Ado-Ekiti, Nigeria under my supervision during the 2014/2015 academic session.
Student’s sinature
Supervisor: Date
Prof. Falaki S.O.
Supervisor: Date
Engr. Omitola O.O.
HOD EEE/COMP: Date:
Prof. Olowolafe J.O

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DEDICATION
This report is dedicated to the Almighty God, the giver of life, the beautifier of destiny and the
dispenser of knowledge for His loving kindness, tender mercies, daily blessing, protection and
journey mercies since the commencement of my programme in this University. I also dedicate it
to my parent through whom God gave my life a shape. They have been there for me since I was
born and never denied me of education. May Almighty God continue to strengthen them
financially and make them healthy to reap the fruit of their labour. I also dedicate this report to the
founder of AfeBabalola University, Are AfeBabalola because without him there is no AfeBabalola
University and without AfeBabalola University, there might not have been this opportunity in my
life and in the life of other students. I also dedicate it to Mrs. Olawumi Kaka who is my tutor since
I have been admitted to this wonderful University.

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ACKNOWLEDGEMENT
I appreciate God, the greatest researcher, the creator of all things and the one that has always led
me through the path of the unknown. He has been faithful in the journey of my life. I am so grateful
to Him because His decision for design is not subjected to shear forces or bending moments, His
understanding is more than what human understanding can fathom. I give glory to the Trinity, who
can treat all cases, there is no way I can honor Him enough for all He has done for me.
My special appreciation goes to my supervisors Prof. Falaki S.O. and Engr. Omitola O.O. and to
my lecturers whose fatherly and motherly advice, devotion, guidance, sacrifice, suggestions,
understanding, technical advice, mentoring and patience in reading and correcting my write up
despite their tight schedule at all various stages of the work which have made the success of the
research a reality. Thank you for your valuable contribution.
Many thanks to the provost college of engineering Prof. I.E. Owolabi for his contributions, I am
also indebted to all-academic and Non-academic staff of Electrical/Electronic and Computer
Engineering Department for their immense contribution to my life and to this research work.
My profound gratitude also extends to my colleagues for their moral support and contribution to
my life.
Finally, I will forever be grateful to my parents Alh. &Alh.K.A. Omosanya for their financial,
moral, parental and spiritual support.

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ABSTRACT
This project is about the design and construction of 2KW 230 volts solar panel inverter at a
frequency of 50Hz.
The device is constructed with locally sourced components and materials of regulated standard.
The basic principle of its operation is a simple conversion of 12V DC from a battery using
integrated circuits and semiconductors at a frequency of 50Hz, into a 230V AC across the windings
of a transformer. A solar panel is used to charge the battery using a solar charge controller.
This project (device) offers a better alternative to Public Power Supply, Generators as well as UPS
considering it is cost effective, noiseless and easy maintainability.

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LIST OF FIGURES
Figure 2.1 shows the circuit diagram designed by SwagatamMajumdar 9
Figure 2.2 shows the IC SG3524 12
Figure 2.3shows the IC 4066 13
Figure 2.4 shows the variable resistor 15
Figure 2.5 shows the fixed resistor 17
Figure 2.6 shows the diode IN4007 18
Figure 2.7 shows the capacitor 19
Figure 2.8 shows the NE555 Timer 20
Figure 2.9 shows the Transistor 21
Figure 2.10 shows the LM393 Comparator 23
Figure 2.11 Shows the LM317 Regulator 24
Figure 3.1 shows the Solar Panel Inverter Block Diagram 26
Figure 3.2 schematic diagram of solar panel connected to the battery 31
Figure 3.3 schematic diagram of solar panel connected to the battery with solar regulator 32
Figure 3.5 Schematic diagram of an Inverter 34
Figure 3.4 Show the complete circuit diagram of the 2KW solar panel inverter 35
Figure 3.6 shows the primary and secondary winding of a transformer 40

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Figure 4.1 shows the inverter casing 45

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CERTIFICATION i
DEDICATION ii
ACKNOWLEDGEMENT iii
ABSTRACT iv
LIST OF FIGURES v
CHAPTER ONE 1
INTRODUCTION 1
1.1 Background 1
1.2 Statement of Problem 2
1.3 Aim and Objectives 2
1.3.1 Aim 2
1.3.2 Objectives 2
1.4 Scope of Study 3
1.5 Significance of the Project 3
1.6 Inverters 4
1.6.1 Central Inverters 4
1.6.2 Micro Inverters 5

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1.7 The BOS (Balance of System) 5
1.8 Solar Panels 6
1.8.1 Solar Panel Poly or Mono 6
CHAPTER TWO 7
LITERATURE REVIEW 7
2.1 INTRODUCTION 7
2.2 Components used for the design 10
2.2.1 IC SG3524 10
2.2.1.1 Description 10
2.2.1.2 Features 11
2.2.1.3 Overview 11
2.2.2 IC 4066 12
2.2.2.1 General Description 12
2.2.2.2 Features 12
2.2.3 Variable Resistor 13
2.2.3.1 Variable Resistor Connection 13
2.2.3.2 Types of Variable Resistor 14

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2.2.3.3 Uses of variable Resistors 15
2.2.3.4 Preset Variable Resistor 15
2.2.4 Fixed Resistor 16
2.2.5 Diode IN4007 17
2.2.5.1 Features 18
2.2.5.2 Typical applications 18
2.2.6 Capacitor (47uf/50v, 10uf/50v) 18
2.2.7 Transistor (BD139, C1815, A1015) 20
2.2.7.1 Description (BD139) 20
2.2.7.2 Features (BD139) 20
2.2.7.3 Features (C1815) 20
2.2.7.4 Features (A1015) 20
2.2.8 Timer (NE555) 21
2.2.8.2 Features 21
2.2.8.3 Application Information 21
2.2.9 Comparator (LM393) 22

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2.2.9.2 Features 23
2.2.10 Regulator (LM117/LM317) 24
2.2.10.2 Features 25
2.2.11 MOSFET 25
CHAPTER THREE 27
METHODOLOGY 27
3.1 Block Diagram of the System 27
3.2 System Operation with block diagram 27
3.3 Calculating the load 28
3.3.1 Types of Load 29
3.4 Calculate the Size of Solar Panels to Supply the Load 30
3.4.1 Peak Sun Hours 31
3.5 Solar Panel Positioning 31
3.5.1 Connecting Your Solar Panels – Direct Connection 32
3.6 Solar Regulators 32
3.7 Solar Panel Sizing 33

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3.8 Determination of the Oscillating Frequency 34
3.9 The Drain Current of the MOSFET 34
3.10 Design of the Inverter Circuit 36
3.11 The Battery 36
3.12 The AC Mains Supply 38
3.13 The AC Mains Sensor 38
3.14 The Oscillator 39
3.15 The Driver and the Output Amplifier 39
3.16 The Inverter Transformer 39
3.16.1 Working Principle of Transformer 40
3.16.2 Faraday's Laws of Electromagnetic Induction 40
3.16.3 Main Constructional Parts of Transformer 41
3.17 The battery Charger 42
3.18 The Change Over 42
3.19 Inverter AC Output 43
3.20 Protections 43
3.21 Indicators 43

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3.22 Switch 43
CHAPTER FOUR 44
RESULTS AND DISCUSSION 44
4.1 Discussion 44
4.2 Testing of the Inverter under load condition 45
4.3 Construction 45
4.4 Casing 46
CHAPTER FIVE 47
CONCLUSION AND RECOMMENDATION 47
5.1 CONCLUSION 47
5.2 RECOMMENDATION 47
REFERENCE 48

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CHAPTER ONE
INTRODUCTION
1.1 Background
The solar inverter is a critical component in a solar energy system. It performs the conversion of
the variable DC output of the Photovoltaic (PV) module(s) into a clean sinusoidal 50 or 60 Hz AC
current that is then applied directly to the commercial electrical grid or to a local, off-grid electrical
network. A solar cell (also called photovoltaic cell) is the smallest solid-state device that converts
the energy of sunlight directly into electricity through the photovoltaic effect. A Photovoltaic (PV)
module is an assembly of cells in series or parallel to enlarge or increase voltage and/or current. A
Panel is an assembly of modules on a structure. An Array is an assembly of panels at a site.
Typically, communications capability is included so users can monitor the inverter and report on
power and operating conditions, provide firmware updates and control the inverter grid
connection.
At the heart of the inverter is a real-time microcontroller. The controller executes the very precise
algorithms required to invert the DC voltage generated by the solar module into AC. This controller
is programmed to perform the control loops necessary for all the power management functions
necessary including DC/DC and DC/AC. The controller also maximizes the power output from
the PV through complex algorithms called maximum power point tracking (MPPT). The PV
maximum output power is dependent on the operating conditions and varies from moment to
moment due to temperature, shading, soilage, cloud cover, and time of day so adjusting for this
maximum power point is a continuous process. For systems with battery energy storage, the

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controller can control the charging as well as switch over to battery power once the sun sets or
cloud cover reduces the PV output power. (Aditee P. Bapat et al 2013)
1.2 Statement of Problem
If there is one factor that has perpetually maintained the status of Nigeria as a less developed
country, it is its electricity sector.Till date, many households and businesses cannot be guaranteed
of 24 hours supply of electricity from the public grid. At this stage of Nigeria’s social and economic
development, the country cannot deliver adequate energy to the citizens despite huge financial
resources that have been expended in the sector.
Rather, Nigerians have continued to rely on electricity generators for their power supply, fuel
marketers are taking significant portion of households’ and businesses’ incomes to supply power,
noise pollution from regular humming generators have become integral part of living for many
Nigerians with imaginable consequences on their health. Because of these problems, there is a
need to design and construct the solar panel inverter which will complement the electricity supply
from the public grid. It is less noisy and does not have any consequence(s) on human health.
(Lookman Oshodi 2014)
1.3 Aim and Objectives
1.3.1 Aim
The aim of this project is to design and construct a 2000Watt solar panel inverter.
1.3.2 Objectives
The objectives of this project are;
1. To provide efficiency, steadiness in the use of power appliances, by ensuring continuous
availability of power supply even in the absence of mains.

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2. To eliminate all suspense from mains outage during the execution of an important and
urgent assignment as may be required.
3. To design a simple and rugged technology; this will utilize the appropriate use of home or
local electrical appliances.
1.4 Scope of Study
This solar power source makes it possible to provide a clean reliable supply of alternative
electricity free of sags or surges which could be found in the line voltage frequency (50Hz). This
project design aims at creating a 2000watts power source which can be utilized as a regular power
source by remote rural industries and private individuals at home or in the office. This project
involves the design and construction of a 2000Watt Solar PV (photovoltaic) system which involves
a solar panel, car battery and an inverter. Furthermore, as a consumer is generating his or her own
electricity they also will benefit from a reduction in their electricity bills.
1.5 Significance of the Project
The solar inverter is the second most important (and second most expensive) component of a solar
PV system. It’s important because it converts the raw Direct Current (DC) solar power that is
produced by your solar panels into Alternating Current (AC) power that comes out of the wall
sockets. Inverters also have technology that maximizes the power output of that DC energy.
The use of solar power has many advantages. First, the energy from the sun is free and readily
accessible in most parts of the world. Moreover, the sun will keep shining until the world's end.
Also, silicon from which most photovoltaic cells are made is an abundant and nontoxic element
(the second most abundant material in the earth's crust).

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Second, the whole energy conversion process is environmentally friendly. It produces no noise,
harmful emissions or polluting gases. The burning of natural resources for energy can create
smoke, cause acid rain and pollute water and air. Carbon dioxide, CO2, a leading greenhouse gas,
is also produced in the case of burning fuels. Solar power uses only the power of the sun as its
fuel. It creates no harmful by-product and contributes actively to the reduction of global warming.
1.6 Inverters
The inverter takes DC power from the charged battery bank and converts it to AC power for the
typical household lights and appliances. Once the number of watt-hours required for a day is
determined, the peak loads need to be ascertained to properly size the inverter. This is the amount
of watts used based on all appliances and loads that will be running at one time. A water pump
and washing machine motor is an example of what may be the peak load requirements. A 1/2 HP
(horse power) pump and washing machine will use about 1875 (adjusted) watts per hour. If this
represents the total peak loads, an inverter that will be able to supply at least 1875 watts of
continuous power from the battery bank; say one in the 2000 watt range will be needed. It's a good
idea to start out the system with the size of inverter you plan to grow into, as upgrading to newer,
larger models is costly. (Pure Energies 2014)
There are two basic types of inverters.
1.6.1 Central Inverters
Central inverters are well-tested and reliable systems that have been around for decades. These are
the most common types of inverters. With central inverters, every solar panel is wired in a “string”
to the inverter box. The conversion from DC to AC occurs at one central location, such as a garage.

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Because the solar panels are wired in “series,” each panel’s power output depends on all of the
panels working. For example, In a string of Christmas tree lights. If one bulb goes out, the whole
string of lights go out until the bad bulb is replaced. So, if shade from a tree covers one panel, it
can seriously diminish the power produced by the whole solar system until the shade clears. This
is why an accurate shade analysis is so important.
1.6.2 Micro Inverters
Micro inverters are relatively new to solar. Instead of converting the DC to AC power at a central
location, micro inverters are installed right under each solar panel. The main advantage to micro
inverters is the ability for each solar panel to transmit power into the house. In other words, each
panel produces its own solar power and keeps producing out solar watts regardless of what
happening to the panel beside it. The down side of micro inverters is that they can be more
expensive and take more labour cost to replace each inverter. Also, because they are so new, micro
inverter reliability is unproven outside of lab testing. (Pure Energies 2014)
1.7 The BOS (Balance of System)
There are many other less well known and less expensive parts to a solar system. Installers
typically wrap these up into “The BOS” or “Balance of System.”
The balance of system includes components such as wiring, emergency DC disconnects, system
monitoring hardware, the frames or “racking” that holds your panels to the roof and at the right
angle, nuts, bolts, roof “flashing” to prevent leaks, and more. (Pure Energies 2014)

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1.8 Solar Panels
Solar Panels can be used for charging your batteries. They provide a good solution for those that
want to be self-sufficient and go on long camping missions through remote areas. They are
available in various voltage and power ratings. More than one solar panel can be used in parallel
to combine their power output. Solar panels joined in parallel work most efficiently if they are the
same. If they are the same, you can design it so that they both generate power at their optimal
operating points. Mixing different panels together gives a compromised operating point. It will
work but the panels will not operate as efficiently.
1.8.1 Solar Panel Poly or Mono
Silicon solar panels have two basic construction methods – polycrystalline or monocrystalline.
There are slight differences between poly and mono cells. Mono are slightly more expensive,
require more energy to make, and are slightly more efficient. Poly are slightly cheaper, use less
energy to make so are better for the environment, are slightly less efficient but have a slightly
better temperature coefficient. That means at elevated temperatures the poly cells become more
efficient.
The differences are only slight. It is largely irrelevant. A solar panel with good efficiency and good
temperature coefficient is to be used whether it is poly or mono, it does not matter.

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CHAPTER TWO
LITERATURE REVIEW
2.1 INTRODUCTION
The use of the sun’s energy is nothing new and dates back to the beginning of time. In recent years
however, the focus on energy consumption worldwide rapidly encourages the research and
development of an alternative fuel source including the sun, wind, hydro, wave, geothermal,
hydrogen and other forms of energy. And today, because of that focus, the use of solar energy is
expanding by leaps and bounds especially since sunlight is free, unlimited, readily available, clean
and reliable.
A solar power system is one which is capable of converting the absorbed sun energy; store it in a
lead acid cell to be used on the load. In this part of the world, where power supply is not effective
and efficient, the use of solar power supply is of immense value and advantage considering the
fact that we are blessed or rich in sun light i.e. high degrees of temperatures which is the main
thing that feeds a solar power supply unit for uses. It is low cost compared to other alternative
sources of power supply in this society e.g. the use of generators which consume fuel or diesel and
are really expensive, and its life span is better and reliable when used under or within or above the
stipulated rating of the solar power device. (Ezugwu 2012)
SwagatamMajumdar, 2012 did a homemade 2000 VA power inverter circuit. He explained that
making a power inverter rated above 500 VA is always difficult, mainly because of the involved
transformer dimension which becomes quite huge, unmanageable and difficult to configure
correctly.
Power inverters in the range of KVA, requires huge current transferring capabilities for

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implementing the required operations as per the desired specifications of the unit.
Transformer being the main power making component of such an inverter, requires high current
handling secondary winding if the used battery voltage is at the lower side, for example 12 or 24
volts. In order to optimize the transformer at lower currents, the voltage needs to be pushed at
higher levels which again becomes a problem, because higher voltage means putting batteries in
series. The above problems can definitely demoralize any new electronic hobbyists or anybody
who might be planning to make a rather big inverter design, may be for controlling the whole
house electrical. An innovative approach for making things simpler even with huge power inverter
designs has been discussed which uses smaller discrete transformers with individual drivers for
implementing a 2000 VA inverter circuit. He studied the circuit diagram below and its operations
with the following points: Basically the idea is to divide the power into many different smaller
transformers whose outputs can be fed to individual sockets for operating the relevant electrical
appliances. This method helped him to avoid the need of hefty and complicated transformers, and
the proposed design becomes feasible even for an electronic novice to understand and construct.
Four IC4049s have been employed in this design. A single 4049 consists of 6 NOT gates or
inverters, so in all 24 of them have been used here.
Two of gates are wired up for generating the basic required square wave pulses and the rest of the
gates are simply held as buffers for driving the next relevant stages. Each transformer utilizes a
couple of gates and the respective high current Darlington transistors which function as the driver
transistors. The associated gates conduct alternately and drive the transistors in accordance.
The MOSFETs which are connected to the driver transistors respond to the above high current
signals and start pumping the battery voltage directly into the winding of the respective
transformers. Due to this an induced high voltage AC starts flowing through the complementary

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output winding of all the involved transformers, generating the required AC 220 V or 120 V at the
respective outputs. These voltages become available in small sockets, so only the relevant
magnitude of power can be expected from each of the transformers. The 555 section takes care of
the square wave output generated from the oscillator stage such that these are broken into sections
and optimized for replicating a modified sine wave output. All the parts after POINT X in the
circuit diagram below should be repeated for acquiring discrete power output sections, the
common input of all these stages must be joined to POINT X. Each of the transformer may be
rated at 200 VA, so together, 11 stages (after pointX) would provide roughly outputs up to 2000
VA. Though using many transformers instead of a single transformer might look like a small
drawback, the actual need of deriving 2000 VA using ordinary parts and concepts finally becomes
easily achievable from the above design. (SwagatamMajumdar2012)
Figure 2.1 shows the circuit diagram designed by SwagatamMajumdar(SwagatamMajumdar
2012)

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Ezugwu (2012) designed and constructed a 200W solar system. The 200W solar system was
determined by load assessment, solar panel number determination, battery requirement and then
inverter sizing. A complete solar panel rated at 200w was however purchased, together with 2
number 150A solar battery, 1500W inverter and also 10A charge controller. These were assembled
together with necessary protective gadgets like cut out switches; to give the 200W expected. The
solar panel was mounted outside a building to allow for maximum collection of sun energy. It is
expected that the system will help her department meet up with its office duties even when central
power is not available.
2.2 Components used for the design
For this project to be completed there is a need to know the components used for the design. These
include:
2.2.1 IC SG3524
2.2.1.1 Description
The SG3524 and SG2524 devices incorporate all the functions required in the construction of a
regulating power supply, inverter, or switching regulator on a single chip. They also can be used
as the control element for high-power-output applications. The SG3524 and SG2524 were
designed for switching regulators of polarity, transformer-coupled dc-to-dc converters,
transformerless voltage doublers, and polarity-converter applications employing fixed-frequency,
pulse-width modulation (PWM) techniques. The complementary output allows either single-ended
or push-pull application. Each device includes an on-chip regulator, error amplifier, programmable
oscillator, pulse-steering flip-flop, two uncommitted pass transistors, a high-gain comparator, and
current-limiting and shutdown circuitry. (Texas instrument 2014)

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2.2.1.2 Features
1. Complete Pulse-Width Modulation (PWM) Power-Control Circuitry.
2. Uncommitted Outputs for Single-Ended or Push- Pull Applications.
3. 8mA Standby Current.
2.2.1.3 Overview
SG3524 is a fixed-frequency pulse-width-modulation (PWM) voltage-regulator control circuit.
The regulator operates at a fixed frequency that is programmed by one timing resistor, RT, and
one timing capacitor, CT (capacitor terminal). RT (resistor terminal) establishes a constant
charging current for CT. This results in a linear voltage ramp at CT, which is fed to the comparator,
providing linear control of the output pulse duration (width) by the error amplifier.
The SG3524 contains an onboard 5-V regulator that serves as a reference, as well as supplying the
SG3524 internal regulator control circuitry. The internal reference voltage is divided externally by
a resistor ladder network to provide a reference within the common-mode range of the error
amplifier as or an external reference can be used.
The output is sensed by a second resistor divider network and the error signal is amplified. This
voltage is then compared to the linear voltage ramp at CT. The resulting modulated pulse out of
the high-gain comparator then is steered to the appropriate output pass transistor (Q1 or Q2) by
the pulse-steering flip-flop, which is synchronously toggled by the oscillator output. The oscillator
output pulse also serves as a blanking pulse to ensure both outputs are never on simultaneously
during the transition times. The duration of the blanking pulse is controlled by the value of CT.

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Figure 2.2 shows the IC SG3524
2.2.2 IC 4066
2.2.2.1 General Description
The CD4066BC is a quad bilateral switch intended for the transmission or multiplexing of analog
or digital signals. It is pin-for-pin compatible with CD4016BC, but has a much lower “ON”
resistance, and “ON” resistance is relatively constant over the input-signal range.
2.2.2.2 Features
1. Wide supply voltage range 3V to 15V.
2. High noise immunity 0.45 VDD.
3. Wide range of digital and ± . PEAKanalog switching.
4. “ON” resistance for 15V operation 80Ω.
5. Matched “ON” resistance ∆RON =5Ω over 15V signal input.
6. “ON” resistance flat over peak-to-peak signal range.
7. High “ON”/“OFF” 65 dB output voltage ratio at F=10 kHz, RL=10 kΩ.
8. Control Line Biasing: Switch On (Logic 1), VC=VDD; Switch Off (Logic 0), VC=VSS.
9. High degree linearity 0.1% distortion.
10. Extremely low “OFF” 0.1 nA switch leakage.
11. Extremely high control input impedance 1012
Ω.

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Figure 2.3shows the IC 4066
2.2.3 Variable Resistor
Variable Resistor is an electronic component. It is applied in an electronic circuit for adjusting
circuit resistance to control voltage or current of that circuit or part of that circuit. The electrical
resistance is varied by sliding a wiper contact along a resistance track. Sometimes the resistance
is adjusted at preset value as required at the time of circuit building by adjusting screw attached to
it and sometimes resistance can be adjusted as when required by controlling knob connected to it.
The active resistance value of the variable resistor depends upon the position of the slider contact
on the resistance track.
It mainly consists of a resistance track and a wiper contact. The wiper contact moves along the
resistance track when adjustable component is adjusted. There are mainly three different types of
resistance track used in this resistor they are carbon track, cermet (ceramic and metal mixture)
track and wire wound track. Carbon track and cermet track are used for high resistance application
whereas wire wound track is used for low resistance variable resistor. The resistance tracks
generally are of circular shape but straight track is also used in many cases. (Electrical4u 2014)
2.2.3.1 Variable Resistor Connection
It is used as a rheostat when one end of the resistance track and wiper terminal is connected to the
circuit and other terminal of resistance track remains open. In this case the electrical resistance

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between connected terminal and wiper terminal depends upon the position of the wiper (slider) on
the resistance track. A variable resistor can also be used as a potentiometer when both ends of the
resistance track are connected to the input circuit and one of the said ends of resistance track and
wiper terminal is connected to the output circuit. In this case all three terminals are in use.
Sometimes in electronics circuit there may be requirement of adjustable resistance but this
adjustment is required only once or very often. This is done by connecting preset resistors in the
circuit. Preset resistor is one kind of variable resistor whose electrical resistance value can be
adjusted by adjusting an adjustable screw attached to it. (John 2010)
2.2.3.2 Types of Variable Resistor
Resistance track wise there are mainly two types of resistance track available one is linear track
and other is logarithmic track. In linear track the resistance value varies linearly with changing
slider position on the track. That means the resistance and the position of slider, form a straight
line characteristics curve. When the resistance of variable resistor, varies logarithmically with
position of the slider contact on the resistance track, the track is referred as logarithmic track.
The resistance value and type of track are marked on the resistor itself. For example when a
variable resistor is marked as 5K9 LIN means it has maximum 5.9 kilo Ω resistance and has a
linear resistance track. Again when a resistor is marked as 2M LOG, it will have maximum
2megaΩ resistance and it has logarithmic track. Preset resistors are linear track type.
But the variable resistors used for volume control in sound system are mainly LOG type as our
ears have logarithmic response to the loudness. In GOL resistor, the resistance changes slowly at
beginning and rapidly at towards end of the track. (John 2010)

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2.2.3.3 Uses of variable Resistors
A variable resistor can be used mainly in two different ways. When one end of resistance track
and wiper terminal is connected with circuit then current through the resistor limits according to
the position of the wiper contact on the resistance track. As the wiper contact slides away from the
connected end of the resistance track, the resistive value of the resistor increases and current goes
down through the circuit. That means the variable resistor behaves like a rheostat.
Another use is as potentiometer. In this case the two ends of resistance track are connected with a
voltage source. Hence voltage drop across the resistance track is equal to the value of voltage
source. Now the output or load circuit is connected across one end of the resistance track and wiped
terminal. Hence voltage across the load terminals is the fraction of source voltage and it depends
upon the position of the wiper terminals on the resistance track. This is another widely used
application of variable resistors. This is needless to say; potentiometers are used to control voltages
whereas rheostats are used to control electric currents. (John 2010)
2.2.3.4 Preset Variable Resistor
This is micro version of variable resistor. Preset resistors are directly mounted on circuit board and
adjusted only when the circuit is built. There is an adjustable screw attached to the resistor and a
small screwdriver is required to adjust this screw for desired resistance value. These resistors are
quite cheaper than standard variable resistor available in the market.

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Figure 2.4 shows the variable resistor
2.2.4 Fixed Resistor
A fixed resistor is part of an electric circuit and is used to reduce the flow of electricity. Resistance
is measured in Ohms and is typically shown as the number and then the units; for example, a 750
Ohm resistor would be written as 750-Ohm. The size of the resistor is based on the number of
Ohms, and it can range from pin to book size.
Resistors come in two classes: fixed and variable. A fixed resistor is set at a specific value and
cannot be changed. A variable resistor is able to manage flows at a specific level and below. This
is an important distinction and determines when and where a resistor should be used.When
selecting a resistor, it is important for a person to consider three things: the value of the resistor,
its tolerance, and its power rating. The value is measured in Ohms. The tolerance indicates the
upper and lower bounds of actual performance, which is measured in plus and minus percentage.
For example, a tolerance of 10% means that the resistor performs within a 10% range of the
resistance value listed in the specifications.Power rating shows the upper limit of power that can
be managed by the resistor and is measured in watts. To calculate the power, a person can multiply
the resistance value of the resistor by the square root of the current. If the power rating is exceeded,
the resistor will fail. A rule of thumb is to use a resistor with a power rating two times higher than
the actual power needed.

17
There are two kinds of fixed resistors: carbon and metal film. Carbon film resistors are designed
for general use and are fairly cheap to produce and purchase. These units have a tolerance of 5%,
with power ratings of 1/8 Watts (W), 1/4W, and 1/2W. The primary issue with this type of resistor
is the fact they generate electrical noise.
A metal film resistor is best used when a higher tolerance is required. These units have a greater
level of accuracy than carbon film resistors, due to the nature of the materials used. There is a
corresponding increase in price, but it may be well worth the incremental cost to protect the other
components of the circuitry.When reviewing the different types of resistors, individuals should
think about the intended use of the circuit. They should select a manufacturer with a good
reputation for quality and consistency, and take the time to test the resistor and the circuit before
installation to ensure all the specifications are correct. (Carol Francois, 2015)
Figure 2.5 shows the fixed resistor
2.2.5 Diode IN4007
A diode is an electronic component with two electrodes (connectors). It acts like a gate or a valve,
allowing electricity to go in one direction, but eventually some of the current will flow in the
opposite direction, at the initial level of operation.
Diodes can be used to convert alternating current to direct current (Diode bridge). They are often
used in power supplies and sometimes to decode amplitude modulation radio signals (like in a

18
crystal radio). Light-emitting diodes (LEDs) are a type of diode that produce light and are used in
many places. Today, the most common diodes are made from semiconductor materials such as
silicon or sometimes germanium. (Diodes incorporated, 2015)
2.2.5.1 Features
1. Diffused Junction.
2. Surge Overload Rating to 30A Peak.
3. Low Reverse Leakage Current.
4. Low forward voltage drop.
5. High forward surge capability.
2.2.5.2 Typical applications
For use in general purpose rectification of power supplies, inverters, converters and freewheeling
diodes application.
Figure 2.6 shows the diode IN4007
2.2.6 Capacitor (47uf/50v, 10uf/50v)
Capacitor is a device for the storage of electric charge. Simple capacitors consist of two plates
made of an electrically conducting material (e.g., a metal) and separated by a nonconducting
material or dielectric (e.g., glass, paraffin, mica, oil, paper, tantalum, or air). The Leyden jar is a

19
simple capacitor. If an electrical potential (voltage) is applied to the plates of a capacitor (e.g., by
connecting one plate to the positive and the other to the negative terminal of a storage battery), the
plates will become charged, one positively and one negatively. If the externally applied voltage is
then removed, the plates of the capacitor remain charged, and the presence of the electric charge
induces an electrical potential between the plates. This phenomenon is called electrostatic
induction. The capacity of the device for storing electric charge (i.e., its capacitance) can be
increased by increasing the area of the plates, by decreasing their separation, or by changing the
dielectric. The dielectric constant of a particular dielectric is the measure of the dielectric's unit
capacitance. It describes the ratio of the capacitance of a dielectric-filled capacitor to a capacitor
of the same size with a vacuum between the plates. Capacitors are used in many electrical and
electronic devices. The main capacitor classifications are non-polarized (used for AC circuits) and
polarized (used for DC circuits). Capacitors can also be classified as fixed or variable. One type of
variable capacitor, formerly used in radio and television tuning circuits, consisted of two sets of
semicircular plates, one fixed and the other mounted on a movable shaft. By rotating the shaft the
area of overlap of the two plates increases or decreases, thus increasing or decreasing the
capacitance. These devices have largely been replaced by frequency synthesizers and a special
type of solid-state diode, known as a varactor, whose capacitance changes with the reverse-biased
voltage across it.
Figure 2.7 shows the capacitor

20
2.2.7 Transistor (BD139, C1815, A1015)
Give brief explanation about transistor first
2.2.7.1 Description (BD139)
These epitaxial planar transistors are mounted in the SOT-32 plastic package. They are designed
for audio amplifiers and drivers utilizing complementary or quasi-complementary circuits.
The NPN types are the BD135 and BD139, and the complementary PNP types are the BD136 and
BD140. (Elite Enterprises H.K, 2015)
2.2.7.2 Features (BD139)
1. It is a complement to BD136, BD138 and BD140 respectively.
2. Products are pre-selected in DC current gain
2.2.7.3 Features (C1815)
1. It has a power dissipation of 0.2W
2. It has a collector current 0.15A
3. It has a collector-base voltage 60V
2.2.7.4 Features (A1015)
1. It has high voltage and high current.
2. Excellent Linearity.
3. Low noise.
4. It is complementary to C1815

21
Figure 2.7 shows the Transistor
2.2.8 Timer (NE555)
2.2.8.1 Description
The NE555 is a highly stable device for generating accurate time delays or oscillation. Additional
terminals are provided for triggering or resetting if desired. In the time delay mode of operation,
the time is precisely controlled by one external resistor and capacitor. For a stable operation as an
oscillator, the free running frequency and duty cycle are accurately controlled with two external
resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the
output circuit can source or sink up to 200 mA. (Texas Instrument 2014)
2.2.8.2 Features
1. Timing from microseconds to hours.
2. Astable or monostable operation.
3. Adjustable duty cycle.
4. Compatible output can sink or source up to 200 mA.
2.2.8.3 Application Information
The NE555 timer devices use resistor and capacitor charging delay to provide a programmable
time delay or operating frequency.

22
Figure 2.8 shows the NE555 Timer
2.2.9 Comparator (LM393)
Low Offset Voltage Dual Comparators
The LM393 series are dual independent precision voltage comparators capable of single or split
supply operation. These devices are designed to permit a common mode range to ground level
with single supply operation. Input offset voltage specifications as low as 2.0 mV make this device
an excellent selection for many applications in consumer, automotive, and industrial electronics.
2.2.9.1 Description
The LM393 series consists of two independent precision voltage comparators with an offset
voltage specification as low as 2.0mV max. For two comparators which were designed specifically
to operate from a single power supply over a wide range of voltages. Operation from split power
supplies is also possible and the low power supply current drain is independent of the magnitude
of the power supply voltage.
These comparators also have a unique characteristic in that the input common-mode voltage range
includes ground, even though operated from a single power supply voltage.

23
The LM393 series was designed to directly interface with TTL and CMOS. When operated from
both plus and minus power supplies, the LM393 series will directly interface with MOS logic
where their low power drain is a distinct advantage over standard comparators.
2.2.9.2 Features
1. Wide Single−Supply Range: 2.0Vdc to 36Vdc.
2. Split−Supply Range: 1.0Vdc to 18Vdc.
3. Very Low Current Drain Independent of Supply Voltage: 0.4 mA.
4. Low Input Bias Current: 25 nA.
5. Low Input Offset Current: 5.0 nA.
6. Low Input Offset Voltage: 5.0 mV (max) LM293/393.
7. Input Common Mode Range to Ground Level.
8. Differential Input Voltage Range Equal to Power Supply Voltage.
9. These Devices are Lead Free, Halogen Free
Figure 2.9 shows the LM393 Comparator

24
2.2.10 Regulator (LM117/LM317)
2.2.10.1 Description
The LM117 series of adjustable 3-terminal positive voltage regulators is capable of supplying in
excess of 1.5A over a 1.2V to 37V output range. They are exceptionally easy to use and require
only two external resistors to set the output voltage. Further, both line and load regulations are
better than standard fixed regulators. Also, the LM117 is packaged in standard transistor packages
which are easily mounted and handled. In addition to higher performance than fixed regulators,
the LM117 series offers full overload protection available only in IC's. Included on the chip are
current limit, thermal overload protection and safe area protection. All overload protection
circuitry remains fully functional even if the adjustment terminal is disconnected.
Normally, no capacitors are needed unless the device is situated more than 6 inches from the input
filter capacitors in which case an input bypass is needed.An optional output capacitor can be added
to improve transient response. The adjustment terminal can bebypassed to achieve very high ripple
rejection ratios which are difficult to achieve with standard 3-terminal regulators. Besides
replacing fixed regulators, the LM117 is useful in a wide variety of other applications. Since the
regulator is “floating” and sees only the input-to- output differential voltage, supplies of several
hundred volts can be regulated as long as the maximum input to output differential is not exceeded,
i.e., avoid short-circuiting the output.
Also, it makes an especially simple adjustable regulator, a programmable output regulator or by
connecting a fixed resistor between the adjustment pin and output, the LM117 can be used as a
precision current regulator. Supplies with electronic shutdown can be achieved by clamping the
adjustment terminal to ground which programs the output to 1.2V where most loads draw little
current. (Texas Instrument, 2014)

25
2.2.10.2 Features
1. Output-currentin excess of 1.5A.
2. Output-Adjustable between 1.2v and 37v.
3. Internal thermal overload protection.
4. Internal short-circuit current limiting.
5. Output-transistor safe operating area compensation.
Figure 2.10 Shows the LM317 Regulator
2.2.11 MOSFET
Discrete power MOSFETs employ semiconductor processing techniques that are similar to those
of today's VLSI circuits, although the device geometry, voltage and current levels are significantly
different from the design used in VLSI devices. The metal oxide semiconductor field effect
transistor (MOSFET) is based on the original field-effect transistor introduced in the 70s. The
invention of the power MOSFET was partly driven by the limitations of bipolar power junction
transistors (BJTs) which, until recently was the device of choice in power electronics
applications.Although it is not possible to define absolutely the operating boundaries of a power
device, we will loosely refer to the power device as any device that can switch at least 1A. The
bipolar power transistor is a current controlled device. A large base drive current as high as one-
fifth of the collector current is required to keep the device in the ON state.

26
Also, higher reverse base drive currents are required to obtain fast turn-off. Despite the very
advanced state of manufacturability and lower costs of BJTs, these limitations have made the base
drive circuit design more complicated and hence more expensive than the power MOSFET.
Another BJT limitation is that both electrons and holes contribute to conduction. Presence of holes
with their higher carrier lifetime causes the switching speed to be several orders of magnitude
slower than for a power MOSFET of similar size and voltage rating. Also, BJTs suffer from
thermal runaway. Their forward voltage drop decreases with increasing temperature causing
diversion of current to a single device when several devices are paralleled. Power MOSFETs, on
the other hand, are majority carrier devices with no minority carrier injection. They are superior to
the BJTs in high frequency applications where switching power losses are important. Plus, they
can withstand simultaneous application of high current and voltage without undergoing destructive
failure due to second breakdown. Power MOSFETs can also be paralleled easily because the
forward voltage drop increases with increasing temperature, ensuring an even distribution of
current among all components. (Duncan A. Grant, 2015)

27
CHAPTER THREE
METHODOLOGY
3.1 Block Diagram of the System
Figure 3.1 shows the Solar Panel Inverter Block Diagram
3.2 System Operation with Block Diagram
The solar panel absorbs energy produced by the sun and converts it into electrical energy. It does
this by absorbing the sun rays into the modules of the solar panel hence produced free electrical
charge carriers in the conduction and valence bands. The electricity produced by the solar panel
was then transferred to the charge controller as shown in fig 3.1 above. The charge controller
regulates the rate at which electric current were drawn in and out of the battery. It turns off charge
when the battery reaches the optimum charging point and turns it on when it goes below a certain
level. It fully charges the battery without permitting overcharge.
SOLAR
PANEL
CHARGE
CONTROLLER
DC/AC
INVERTER/CHARGER
BATTERY
UTILITY
SOLAR
PANEL
UTILITY
PHCN/MAINS

28
The regulated voltage from the charge controller was then transferred to the solar battery. The
batteries were the key component in this solar power system. It provided energy storage for the
system. The energy stored in the batteries was then used to power the load but it was first converted
to AC voltage by the use of an inverter due to they were AC loads. The photovoltaic ally produced
direct current was commuted periodically by controlled oscillatory system and feed to power
electronic semiconductor switches such as transistors which were connected the power
transformer. Here the voltage was stepped up to the desired ac voltage. The inverter could also
charge the battery when there is public power supply.
3.3 Calculating the load
In other to determine the power use of each appliance and howlong they will be operated, the
appliance datasheets or nameplates should be checked. If their consumption is in amps, multiply
by their voltage to yield their power. If they are AC loads driven by an inverter, multiply the power
by 1.1 to take into account the losses in the inverter.
To calculate the total Watthour (Wh) consumed in a 24hr period. Multiply the power consumption
of the appliance by the number of hours it runs per day and sum together with all the other
appliances.
As an example – a large fridge that is rated at an average of 2.1A at 12V, a small fridge used as a
freezer rated at 1A at 12V (double the rated current use when used as a freezer – 2A instead of
1A), an LED light rated at 0.5A at 12V that operates for a couple of hours per day, and an 240V AC
television rated at 180W used for a couple of hours per day.
Large fridge (Wh): . × × = ℎ
Freezer (Wh): × × = ℎ
LED Light (Wh): . × × = ℎ

29
TV (Wh): × . × = ℎ
Total energy consumption over 24hr period: + + + = Wh
3.3.1 Types of Load
1. Resistive Loads: Resistive loads are loads which consume electrical energy in a sinusoidal
manner. This means that the current flow is in time with and directly proportional to the
voltage. It is a load that contains no inductance or capacitance, just pure resistance.
Therefore; when a resistive load is energized, the current rises instantly to its steady-state
value without first rising to a higher value. It includes loads such as incandescent lighting
and electrical heaters.
2. Inductive Loads: An Inductive Load is a load that pulls a large amount of current (an
inrush current) when first energized. After a few cycles or seconds the current "settles
down" to the full-load running current. Inductive loads can cause excessive voltages to
appear when switched. Examples of Inductive Loads are motors, transformers, and wound
control gear.
3. Capacitive Loads: A Capacitive Load is an AC electrical load in which the current wave
reaches its peak before the voltage. Capacitive loads are loads that capacitance exceeds
inductance. Example of a Capacitive Load is the flash of a camera, capacitors, wiring,
cable. (TEPCO 2010)

30
3.4 Calculate the Size of Solar Panels to Supply the Load
The size of solar panels you need is the energy consumption in a 24hr period divided by the number
of hours in a day that the solar panels produce energy for. For number of hours, we use peak sun
hours which is explained below. If we assume we are in a sunny area with 8 peak sun hours per
day we get:
Solar Panel Rating = 1589 / 8 = 199W
So in this case you need around 199W of solar panels. What if it’s cloudy? What if your panels
are dirty? What if your panels are not faced directly at the sun and at the correct angle? What if
you leave the lights on longer than calculated? What about the loss in panel efficiency with
elevated temperatures? What about loss in panel efficiency as they age? What about the fact that
the regulator is not 100% efficient? What about the variation in load from the fridges depending
on ambient temperature? What about variations in irradiation due to season?? What if, at the same
time, I want to chill a carton of warm coca cola, charge a laptop and charge a torch?
So the equation would become incredibly complicated if you were to try to work it all out. You
need to multiply by a fudge factor. The fudge factor is a number anywhere between 1 and infinity.
It’s simply down to probability of running out of power. Assuming you run your system 24 hours
a day 365 days a year, if your fudge factor is 1, then you might run out of power most of the time.
There is no way to guarantee power; you are simply shifting the probability. If you are powering
life critical systems your fudge factor might be 10 or more. A typical fudge factor might be say
1.2. So in our example it changes:
Solar Panel Rating = ÷ × . = 238W

31
3.4.1 Peak Sun Hours
‘Peak sun hours’ is a way to standardize how much sunlight a particular area receives at a particular
time of year. It’s the equivalent number of hours per day when solar irradiation averages 1000
watts per square meter. The units are kWh per square meter per day. I used 9 hours in the
calculation above. Peak sun hours for many places in Nigeria during dry season is around 8 hours.
Some places it is more, some places it is less. Eight is a reasonable estimate for Nigeria in dry
season. What about wet season? In northern cities we might expect 2 to 3 peak sun hours during
wet season. In south, west in wet season we could be around 1.5 to 2 peak sun hours per day. So
we can see there is a lot of variation depending on location and season. This has to be taken into
account when sizing the panels. If the above system needed to work in south-west in the middle
of wet season then, using the same 1.2 fudge factor, the calculation would be:
÷ . × . = W
So we would need around 8 x 130W panels.
3.5 Solar Panel Positioning
The solar panels should be pointed directly to the sun, perpendicular to the sun’s rays. If there are
multiple panels then it is suggested that they should all be positioned the same direction. Actually
each panel individually should be positioned as close as perfectly perpendicular to the sun’s rays
as possible regardless of the position of the other panels. The voltage versus current relationship
and the resistance in the electrical distribution will allow the better positioned solar panels to
provide more energy even if it’s not as much as when all panels are ideally positioned. Of course
the maximum energy is obtained when all panels are ideally positioned in which case they will all
be positioned the same.

32
3.5.1 Connecting Your Solar Panels – Direct Connection
You can connect the solar panels directly to the auxiliary battery. This is the simplest system but
it’s quite a poor arrangement. There is potential to overcharge and damage your battery. A solar
panel will continue to charge to its open circuit voltage, which is usually around 17.5V for panels
used in 12V systems. This is much too high for lead acid batteries and will cause excessive grid
corrosion and pressure venting and damage of the battery. Small panels will still lead to the
overcharge condition, it will just take longer. Another negative aspect to this arrangement is that
the solar panel is not allowed to operate at its optimal voltage. The voltage is clamped to whatever
the battery voltage is. So the solar panel will not be able to achieve its rated power output and it
will take longer to charge your battery.
Figure 3.2 schematic diagram of solar panel connected to the battery
3.6 Solar Regulators
To overcome the limitations of a direct solar panel connection to your auxiliary battery, a solar
regulator is used. Some solar panels come with an integrated solar regulator. Some dual battery
isolator and DC-DC converter vendors also provide solutions for solar charging and distribution.
For the purpose of this project I used a separate third party solar regulator. Solar regulators charge
the battery according to an optimized charging profile, reducing grid corrosion and will terminate

33
the charge at the correct voltage. The best solar regulators are of the type Maximum Power Point
Tracking (MPPT). These regulators load the solar panels according to their optimized current and
voltage characteristics for the given level of irradiation. This ensures your solar panels are
operating as efficiently as possible, providing you with the most energy and highest charge rate
possible. MPPT solar regulators are the best solution for connecting solar panels. To size the solar
regulator, sum the total power output of all the panels together and divide by 12 to give you a
current rating. The solar regulator needs to exceed this value. So for a 130W solar panel that I am
using, the current would be
= . �. (The rating of the solar regulator needs to exceed this).
Figure 3.3 schematic diagram of solar panel connected to the battery with solar regulator
3.7 Solar Panel Sizing
How much solar panel do you need? You can get a rough idea from the loads you want to run. It
is best to work in power when calculating solar panel load. It avoids confusion when running
appliances at different voltages (for example AC appliances through an inverter). The current
provided by a solar panel is also difficult to calculate due to the complexity of their optimized
voltage versus current relationship. So I worked in watts (W) and watt-hours (Wh).

34
3.8 Determination of the Oscillating Frequency
By supplying a constant 12Volt DC through a voltage regulator to the IC SG 3524 PWM, the
frequency of the oscillating signal was determined using a 10KΩ variable resistor connected in
series with another 56KΩ resistor and both connected in parallel with 0.22μF to form the RC time
constant network.
Frequency, f =
. ×CtRf
where
Time Capacitor (CT) = 0.22μF
Fixed Resistor (RF) = 56KΩ
Variable Resistor (VR) = 10KΩ
Time Resistor (RT) = 56KΩ+10KΩ = 66KΩ
Therefore, f =
. × . × −6× × 3
f = 62.6Hz
It should be noted that the variable resistor was varied until the frequency of the signal was 50Hz.
(Omitola et al 2014)
3.9 The Drain Current of the MOSFET
From the Inverter, total power is 2000Watts,
The battery Voltage is = 12V
Therefore, the drain current ID = PV
I =
ID = 166.7A
Where the voltage output of the inverter, Voutput = 230V
Full load output current, Ioutput =
�
�

35
=
Ioutput = 8.7A
Figure 3.4 Show the complete circuit diagram of the 2KW solar panel inverter

36
3.10 Design of the Inverter Circuit
This circuit uses IC SG3524 PWM which functions as oscillator together with TC 4066 BP which
functions as switch to generate the oscillating signal that controls the switching ON and OFF of
the gate of an 8-numbered MOSFETS connected in parallel to a center-tapped transformer. This
switches the 12V DC from the battery, across the windings of the transformer to produce a 230V
AC at 50Hz frequency for the use of computers and other domestic appliances with maximum
power rating of 2000watts.
LM 393 IC (a comparator) and NE555 (a timer) incorporated in the circuit function to detect
overloading and low battery in the inverter. (Omitola et al 2014)
Generally, inverter is a combination of a battery, a charger circuit and an inverting circuit as shown
in the figure 3.5 below.
Figure 3.5 Schematic diagram of an Inverter
3.11 The Battery
The battery used in this project is a two-terminal device that provides 12V DC supply to the
inverter section when the AC mains is not available. This 12V DC is converted to 230V AC supply
to the inverter output socket. (Omitola et al 2014)
It is pertinent to state that lead-acid batteries used in automobiles are very good for this purpose as
they provide good quality power for a long duration and can be recharged once the power stored
DC
power
from
battery
INVERT
ER
CIRCUI
AC power
supply

37
in them are consumed. The backup time provided by the inverter depends on the battery type and
its current capacity. The size of the battery bank will be determined by the daily watt-hour
requirements and the desired days of storage capacity required. Here's a formula for calculating
the battery needs: Take the adjusted watt-hours per day multiplied by the number of days of storage
required; take that figure x 2 (for 50% depth of battery discharge); then divide by the system
voltage = amp hours (ah) of storage needed. For example,Let’s say you need 2000 watt-hours per
day and want 5 days of battery back-up;
× =
� � � =
� = = ℎ �
If you are looking at 65ah capacity, 12V car battery,
ℎ =
So therefore we would need 26 of those 65ah 12V batteries to provide 5 days of back-up, at the
discharge rate of 2000 watts per day, in a 12V system. Ideally, it is recommended not take the
batteries below 30% depth of discharge, and never below 50% depth of discharge. Basically we
need to put a little more power into the batteries than you use (about 120 watts for every 100 watts
you take out). Batteries can be series wired to achieve the voltage desired (i.e. two 6V batteries for
12V, two 12V for 24V, etc.). The lead-acid type of battery does require proper maintenance to
extend their life and work in an optimum fashion. They prefer moderate temperatures around 70

38
degrees; for this reason they should be insulated in cold climates, and well-ventilated in warm
climates. They need to be "equalized" at least three or four times a year, and as often as
monthly. Equalizing refers to a "controlled overcharging" process whereby the voltage of the
batteries is increased to where the accumulated sulfates are "cooked" off the plates and mixed back
into the electrolyte solution. During this process, the battery caps are removed and distilled water
is added as necessary. A hydrometer (tool for checking the specific gravity) is used to check the
electrolyte density of individual battery cells at this time. The equalization voltage for a 12V
system will usually be around 15 volts; for a 24V system, 30 volts.
3.12 The AC Mains Supply
The AC input supplies a 230V AC, 50Hz from the public supply. This is connected to the charger
circuit where it is rectified to DC voltage and through the relay switch to the output of the inverter
to bypass the inverter when there is public electric power supply while the battery is charging.
3.13 The AC Mains Sensor
This inverter uses a 0 - 24V/1Amp triggering transformer and a regulator to sense the AC mains
supply. When the AC mains supply is available, this supply is given to the primary winding of the
triggering transformer to give 24V AC supply at the secondary winding. It is then rectified by
bridge rectifier and input to filter capacitors which convert the 24V AC supply to 24V DC supply
and through the LM317 regulator which regulates the 24V DC to 12V DC. The 12V supply stays
constant even when there is a change in the AC mains supply and the inverter is informed about
the availability of the AC mains supply whenever there is.

39
3.14 The Oscillator
This section uses a pulse width modulator PMW IC SG 3524 to generate the 50Hz frequency
required to generate AC supply by the inverter. The relationship between the frequency, resistance
and capacitance has been given before as:-
Frequency, =
. ×��
The battery supply is connected to the IC SG 3524 through the inverter ON/OFF switch. The flip-
flop converts the incoming signal into signals with changing polarity such that in a two-signal with
changing polarity, the first is positive while the second is negative and vice versa. This process is
repeated 50times per second to give an alternating signal with 50Hz frequency at the output of
SG3524. This alternating signal is known as "MOS Drive Signal ".
3.15 The Driver and the Output Amplifier
The MOS drive signals are given to the base of MOS driver transistor which results in the MOS
drive signal getting separated into two different channels. The transistors amplify the 50Hz MOS
drive signal at their base to a sufficient level and output them from the emitter.
The 50Hz signal from the emitter of each of the transistor is connected to the gate G of all the
MOSFETS in each of the MOSFET channel, through the appropriate resistance.
3.16 The Inverter Transformer
The transformer used for this project has a center-tapping which divides the primary into two equal
sections.
This center-tapping is connected to the positive terminal of the battery. Two ends of the primary
are connected to the negative terminal of the battery through switches S1 and S2. These switches
S1 and S2 are turned ON/OFF alternatively to generate current in the primary coil. When the

40
switch S1 is closed and S2 is opened, the current flows in the first part of the primary winding and
the EMF is induced in the secondary winding. When the switch S2 is closed and S1 is opened, the
current flows in the second part of the primary winding and the EMF of opposite polarity is induced
in the secondary winding. Thus, if the switches S1 and S2 are alternatively opened and closed at
constant rate, then the output from the secondary winding is a square wave of the frequency at
which the switches S1 and S2 are opened and closed. (Omitola et al 2014)
Electrical power transformer is a static device which transforms electrical energy from one circuit
to another without any direct electrical connection and with the help of mutual induction between
two windings. It transforms power from one circuit to another without changing its frequency but
may be in different voltage level. This is a very short and simple definition of transformer.
(Electrical4u, 2015)
3.16.1 Working Principle of Transformer
The working principle of transformer is very simple. It depends upon Faraday's law of
electromagnetic induction. Actually, mutual induction between two or more winding is responsible
for transformation action in an electrical transformer. (Electrical4u, 2015)
3.16.2 Faraday's Laws of Electromagnetic Induction
According to these Faraday's laws, "Rate of change of flux linkage with respect to time is directly
proportional to the induced EMF in a conductor or coil".
Whenever we apply alternating current to an electric coil, there will be an alternating flux
surrounding that coil. Now if we bring another coil near the first one, there will be an alternating
flux linkage with that second coil. As the flux is alternating, there will be obviously a rate of change
in flux linkage with respect to time in the second coil. Naturally, electromotive force will be

41
induced in it as per Faraday’s law of electromagnetic induction. This is the most basic concept of
the theory of transformer.
The winding which takes electrical power from the source is generally known as primary winding
of the transformer. The winding which gives the desired output voltage due to mutual induction in
the transformer is commonly known as secondary winding of the transformer. (Electrical4u, 2015)
Figure 3.6 shows the primary and secondary winding of a transformer (Electrical4u, 2015)
3.16.3 Main Constructional Parts of Transformer
The three main constructional parts are:
1. Primary Winding of Transformer: this part produces magnetic flux when it is connected to
electrical source.
2. Magnetic Core of Transformer: here the magnetic flux produced by the primary winding
that will pass through this low reluctance path linked with secondary winding and create a
closed magnetic circuit.
3. Secondary Winding of Transformer: the flux produced by primary winding passes through
the core will link with the secondary winding. This winding also wounds on the same core
and gives the desired output of the transformer. (Electrical4u, 2015)

42
3.17 The battery Charger
When the inverter section receives AC mains supply, it stops operation but the charger section in
the inverter starts its operation. In this mode, the inverter transformer works as a step down
transformer and output 12V at its secondary winding. During the charging, MOSFET transistors
at the output section works as rectifier with the drain working as the cathode while the source
works as the anode. The center-tapping of the transformer receives positive supply and the
MOSFET source 'S' receives negative supply from the battery. The center-tapping is connected to
the positive terminal of the battery and the MOSFET source S is connected to the negative terminal
with a shunt resistance. Thus, when the inverter receives AC mains supply, inverter transformer
and MOSFET together work as a charger and charge the battery.
3.18 The Change Over
This section is used to switch ON the inverter when the AC mains supply is OFF and to switch
OFF the inverter when the AC mains supply comes back ON. During changeover, when the
inverter receives AC mains supply, it stops drawing the battery supply and the AC mains supply
at the inverter input is directly sent to the inverter output socket. This is done using a one, two-
pole change over relay.
3.19 Inverter AC Output
The AC output gives a 230V AC, 50Hz either directly from the input when the AC mains supply
is available or from the inverter circuit action on the battery when the AC mains supply is not
available. Computers and other household appliances are connected to this output.

43
3.20 Protections
The AC input to this device was fused with a 5Amp fuse to protect the transformer as well as the
rectifying circuit in case of over voltage, and high current which could flow into the transformer.
3.21 Indicators
Five indicators are connected to the front of the inverter; a red colour shows that the inverter is
charging as well as delivering a 230V AC from its output terminal. Green colour indicates that the
inverter is discharging from the battery. Yellow colour indicates that it is inverting. White colour
indicates battery full and the last red colour indicates battery low.
3.22 Switch
A switch is connected to the front of the inverter. This red switch controls the AC voltage input
and output of the inverter.

44
CHAPTER FOUR
RESULTS AND DISCUSSION
4.1 Discussion
The solar panel was placed under the sun, the peak sun radiation was on the panel surface and then
17.5 volts was observed using a multimeter. While observing the voltage, the panel was slightly
adjusted and the voltage varied at an angle away from the sun. The voltage depreciated.
The output from the solar panel was connected to the charge controller with respect to their
polarities and when the output voltage was observed, it read 12.56 volts which was right for
charging 12 volts battery. The voltage was 17.5 volts DC because the solar and the charge
controller were connected without load. Then load was added to the inverter which gave an output
of 230 volts which was left for about 30 minutes. It was observed again and the voltage did not
vary. The inverter has five LED indicators. The first indicator shows if the system is connected to
the mains or not, the second indicator shows if the inverter system is switched ON or OFF, the
third was used to display battery low or if the system experience any fault or not, the fourth
indicator is used to show the battery full and the last indicator is used to show if the inverter is
charging or not.
The inverter also had an additional socket for plugging the inverter to mains to serves as another
means to charge the batteries other than the solar system. When tested with the volt meter as it was
plugged on the mains out, it read 14.4 volts which was basically because of the state of the charge
level of the batteries. The batteries would normally self-discharge over time even when not used.
Since the inverter included a triple cycle charger, it could continue to maintain the battery with

45
equalization charge voltage of about 12 volts just to make sure that the battery does not discharge
even it was on standby mode.
4.2 Testing of the Inverter under load condition
The duration at which the inverter discharges under load condition depends on the total power of
load connected to its output terminal and the power rating of the battery connected to its input
terminal. Bearing in mind that total load must not exceed 1000watts.
Discharge duration
(a) Battery power rating = 12volts, 65Ampere per hour
When total load = 150watts
Therefore duration =
×
= . ℎ
(b) Battery power rating = 12volts, 65Ampere per hour
When load = 300watts
Therefore duration =
×
= . ℎ
4.3 Construction
The step by step approach taking in the construction of this project started with the building of the
transformer from the laminating core, followed by the rectification stage, sensing and monitoring
stage, comparator and transistor switching. The tools and instruments used include:
1. Lead and Soldering Iron
2. Lead sucker
3. Copper stripping knife

46
4. Cutter
5. Razor blade
6. Plier
7. Digital Multimeter
8. Ferro and bread board
To conform to the requirement of this project, temporary construction of the prototype was done
on bread board before finally transferring it onto the Ferro-board for permanent soldering. The
circuit was constructed, tested and put to use under proper load conditions. In other to achieve
accuracy in the design, some necessary adjustments were made to some of the components used.
4.4 Casing
The complete unit was housed in a metallic casing. Battery terminals for positive and negative,
power switch, ventilating ductsand LEDs were fixed in their allotted slots and connected to their
respective points on the circuit. The casing was earthed and each stage carefully arranged inside
and connected together.
Figure 4.1 shows the inverter casing

47
CHAPTER FIVE
CONCLUSION AND RECOMMENDATION
5.1 CONCLUSION
The construction of this 2000Watts (2KW), 220Volts inverter at a 50Hz frequency was a gradual
process from gathering of materials to testing of components. The project was intended to supply
2000 watts of energy to serve as another source of alternative energy besides the diesel engine.
The construction was a successful one and worked efficiently as intended. The solar system
worked effectively and cost no further operational cost. When compared to a 1.5 KVA petrol
generator, it was costly but for the initial expenses. However it was later seen to be cheap since
the system needed no petrol to operate but sunlight which was nature’s free gift. The solar cell
acted as a source of charger to the battery and inverting the power stored using an inverter into
usable power for any load. The power output was usable for many domestic appliances that are
sensitive to having sinusoidal inputs.
5.2 RECOMMENDATION
Although the objectives of this project have been achieved, the inverter cannot be used to power
any device of higher power rating. Increasing the power rating of the inverter by increasing the
number of the power switching devices and the current rating of the transformer would be
recommended. The solar power system was a convenient way of producing an alternative means
of power supply to supplement the mains failure. It was advantageous to user who could afford its
initial cost of installation. There would be need to add up more batteries to meet up with the
running time and the system load capacity since the system had an adjusted wattage. That ismore
batteries could be added to increase the capacity of the system to accommodate more load.

48
REFERENCE
1. Aditee P. Bapat et al (2013). “Concept Design and Feasibility Study of a Grid Free Solar Power
Source for Small Scale Industries in Remote Areas Using Flywheel Batteries” IIT Roorkee,
India, Dec 18-20 2013
2. Carol Francois (2015).''what is a fixed resistor''http://m.wisegeek.org/what-is-a-fixed-
resistor.htm. Retrieved on 14-2-2015.
3. DigitalMind (2014) ‘Solar Power and Off-Grid Living’
http://www.techienation.com/2008/04/11/solar-investigation-how-many-solar-panels-you-
need/. Retrieved on 11-12-2014.
4. Diodes incorporated (2015). ''Diode IN4001-
IN4007''http://www.diodes.com/datasheets/ap02008.pdf. Retrieved on 1-3-2015.
5. Duncan A. Grant and John Gower (n.d). "Power MOSFETs - Theory and Applications". P2-3.
6. Electrical4u (2014). Online Electrical Engineering Study Site. ''Variable
resistors''http://electrical4u.com/variable-resistors/. Retrieved on 11-12-2014.
7. Electrical4u (2015), Online Electrical Engineering Study Site. ‘Transformers-types and
principles’ http://www.electrical4u.com/what-is-transformer-definition-working-principle-of-
transformer/. Retrieved on 6-6-2015.
8. Elite Enterprises (H.K.) Co., Ltd. ‘A1015 PNP Epitaxial Silicon Transistor’.http://info@elite-
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Solar Power System’Caritas University, Amorji-Nike, Enugu, Nigeria.

49
10. Future Electronics Japan(2015). ''what is a fixed
resistor''http://www.futureelectronics.com/en/resistors/fixed-resistor.aspx. Retrieved on 14-2-
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http://www.circuitstoday.com/variable-resistors-working-and-applications. Retrieved on 14-
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development”
http://ledna.org/sites/ledna.org/files/the_nigerian_electricity_sector_and_its_impact_on_led_1.pdf
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Launch Point Technologies, Inc, Goleta, California, USA.
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15. Swagatam Majumdar (2012). ''How to make Homemade 2000va Power''
http://homemadecircuitsandschematics.blogspot.com/2012/03/how-to-make-homemade-
2000-va-power.html. Retrieved on 11-12-2014.
16. TEPCO EGYPT (2010) ‘Types of Loads’ http://www.tepcoegypt.com/Systems-
Energy%20Efficiency%20What%20are%20the%20types%20of%20loads.html. Retrieved on
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50
18. Pure Energies Group (2014). “Solar E uip e t: I ve te s, Sola Pa els a d Su light”.
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on 19-3-2015

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