1.
CONSTRUCTION OF A 2KVA INVERTER
PRESENTED BY:
OBASAN KEHINDE OLUSEGUN EE201300239DPT
FAMORIYO PAUL OLUWADAMILARE EE201300174DPT
SOLAGBADE TOBI OLAYEMI EE201300154DPT
ABOBARIN ADEMUYIWA MUTIU EE201300646DPT
ADESOKAN OLAMIDE ELIJAH EE201300533DPT
NWORIE NNABUIKE CYPRIAN EE201405634DPT
SUPERVISED BY:
ENGR O. G. MOJIBOLA
SUBMITTED TO:
DEPARTMENT OF ELECTRICAL ELECTRONICS ENGINEERING
SCHOOL OF ENGINEERING TECHNOLOGY
FEDERAL POLYTECHNIC, EDE
OSUN STATE.
IN PARTIAL FULFILMENT OF THE REQUIREMENT OF ORDINARY
NATIONAL DIPLOMA CERTIFICATE (OND) IN ELECTRICAL
ELECTRONICS ENGINEERING
DECEMBER 2016

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CHAPTER ONE
1.0 Introduction
This project focuses on conversion of DC to AC power inverter whose aim is to
efficiently convert a DC power source to high voltage AC source, similar to power that
would be available at an electrical wall outlet. Inverters are used for many applications as
in a situation where low voltage DC sources such as batteries solar panel or fuel cells
must be converted so that devices can run on AC power. One example of such a situation
is converting electrical power from a car battery to run a laptop, television, cell phones
e.t.c.
The method in which the low voltage DC power is inverted is completely in two
steps. The first being the conversion of low voltage DC power to a high voltage DC
source, and the second step is being the conversion of the high DC source to an AC
waveform using PWM (Pulse Width Modulation).
Another method to complete the desire outcome would be to first convert the low
voltage DC power to AC and then use a transformer to step up the voltage to 220volts.
However, due to the erratic power supply of electricity in Nigeria, an alternative means of
power supply has to be incorporated to supplement the supply of electricity which one of
such form of power is inverter.

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1.1 Background Information and System Design
From the late 19th century to the middle of 20th century DC to AC conversion was
accomplished using rotary converters, or motor generator (MG) set. In the early 20th
century, vacuum tube and gas filled tube began to be used as switches in inverter circuit.
The most widely use type of tube is thyraton.
The origination of electromechanical inverters explains the source of the term
inverter. Early AC to DC converters used on conduction of synchronous of AC motor
direct connected to a generator (DYNAMO), so that the generator commutation reversed
it connection exactly the right moment to produce DC. A later improvement is the
synchronous converter, in which the generator and motor winding are combined into one
armature which slip rings at one end and the commutation at the other end and only one
field frame.
The result is either with AC-on, DC-out. With an M.G set, the DC can be considered
to be separately generated from the AC with a synchronous converter, in a certain sense,
it can be considered to be mechanically rectified AC. Using the right auxiliary and
control equipment, and motor generator set or rotary converter can “run backward”,
converting DC to AC. Hence, an inverter is inverter converter. It should also be noted
that early inverters did not use transistors for switching purposes, because its voltage and
current ratings were not high enough for most inverter applications.

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However, in 1975, the silicon control rectifier (SCR) was introduced as switches,
hence initiating a transition to solid state inverter circuits. Today, however due to an
increased knowledge in technology, modern inverters are less bulky and more efficient
with the use of various components such as ICs (Integrated Circuits)
1.2 Aims and objectives
The main aim of this project is to design and construct a 2KVA inverter with
12volts supply so as to achieve the following objectives;
i. To ensure the protection of the back-up source consumer equipment and supply.
ii. To back-up the erratic power supply by PHCN.
iii. To modify sine wave that can be used to power appliances both in houses and
industries.
iv. To safely operate any electronic devices (such as micro wave, speed motor) that
require sensitive calibration.
The design and construction of this project was to provide an ample chance for an
understanding of the characteristics, operations, and application of power electronic
devices. In addition, generally it gives an understanding of basic design concept of
inverter based on MOSFET (Metallic Oxide Semiconductor Field Effect Transistor)
switching and PWM (Pulse Width Modulator).

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1.3 Limitation
The major limitation of this project is that it cannot operate equipment or an
electronic device that is above its rated current due to some form of losses during the
circuit operation.

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CHAPTER TWO
2.0 Literature Review
In an inverter circuit, the DC power is connected to a transformer primary through
the center tap of the primary windings. A switch is rapidly switched back and forth to
allow current to flow following two alternate paths through one end of the primary
winding and then the other end. The alternation of the direction of flow of current in the
primary winding of the transformer produces an alternating current in the secondary
winding. The electromechanical version of switching devices includes: two stationary
contact and spring support moving contact.
A power inverter converts DC power or direct current to standard AC power or
alternating current, which facilitates the running electrical equipment of the car, home or
office for mobile application, emergencies or simple convenience. The output voltage
could be fixed or variable voltage and maintaining the DC gain of the inverter constant,
on the other hand, if the DC input voltage is fixed, a variable output voltage can be
obtained by varying the gain of the inverter, which is normally accomplished by PWM
control within the inverter.
Power inverters are great for camping at parks and picnics where electricity is not
or rarely available. The toaster, blender, and printer can all still be used. In a utility
outage, a power inverter can be used for emergency electricity. The radio can be plugged

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in to tune into important alerts, run essential medical equipment, lights or whatever
electronic garget that falls within the inverter's power limits.
2.1 Review on early inverter
In the effort in pursuit of the conversion of DC power to AC power has being
since the late 19th century and from then to the middle 20thcentury;DC to AC power
conversion was accomplished using rotary converter or motor generator set. In the early
20th century, vacuum tubes began to be used as switches in inverter circuit.
First Generation of Inverter
From the invention of inverters, a switching device is usually made use as a means
to switch the transformer to ON/ OFF state in order to generate fast rate frequency.
Silicon controlled rectifier (SCR) is an example of a switching solid electronics
component adopted to ensure the switching of the system to ON/ OFF state at a
considerable faster rate compared to a manual switching. SCR consist of three main
terminals namely; Anode, Cathode and Gate.
When two SCR are connected to a center tapped transformer, current will flow in
positive half cycle (ON current) and negative half cycle (OFF current). This is the same
as the application of Silicon Controlled Rectifier as full wave rectifier.

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Second Generation
This generation made use of multivibrator, amplifier and transformer. The process
takes input from 12VDC source, and runs from the supply to the multivibrator, and from
the multivibrator to the amplifier, and finally to the transformer which gives AC voltage
as output.
This is inverted to a 240V AC, the multivibrator used may be bistable or astable
which have two stage cycles useful for generating square waves and pulses. The 12V DC
source serves as the power supply to the inverter.
Third Generation
In this generation, two 555 timer ICs were used for generating oscillations of
equal frequency. An astable multivibrator is used to switch ON/ OFF, to generate
constant frequency of 50Hz. The frequency generated by each 555 timer ICs is controlled
by the input configuration of the RC circuit. The output from the ICs is amplified by
drivers and then fed to the gate of the MOSFET.
The NE555 timer IC was used to replace the first generation and second
generation inverters due to some difficulties experienced and the inefficiency of its
components.

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2.2 Basic Design Considerations
Some design considerations were fulfilled in the process of designing this project;
which was properly taken cognizance of, in order to meet the design objectives. A close
look at these considerations would reveal that they all emphasize on obvious link
between design and we, the designers. Formulating the right problem is one of the basic
design considerations. It encompasses ensuring that the objective and requirements of the
device, equipment, machine or facility are right to save-guard against possible failure.
Designing an appropriate solution is one of the major factors to be considered in the
course of the project design. It entails ensuring that the system is not only technically
excellent but also appropriate and successful. A lot of work had been done on this project
before finally arriving at the appropriate circuit to be used.
2.3 Review of Difference between Sine Wave and Modified Sine Wave
The Sine Wave Inverter
The electrical circuit of a pure sine wave inverter is far more complex than a
square wave or modified sine wave inverter. Another way to obtain a sine output is to
obtain a square wave output from a square wave inverter and then modify this output to
achieve a pure sine wave. A pure sine wave inverter has several advantages over its
previous two forms.

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More efficiency, hence consumes less power. They can be adjusted according to
your personal power requirements, since several types are available with different power
outputs. The output of a pure sine wave inverter is very reliable, but at the same time,
there is a tradeoff between the price and reliability. Due to this reason they are the best
option for sensitive equipment(fromwww.myprojectcircuit.com/2kva-inverter.htmledited).
Figure 2.1 shows a pure sine wave
The Modified Sine Wave Inverter
The construction of this type of inverter is a bit more complex than a simple
square wave inverter, but still it is a lot simpler than a pure sine wave inverter. A
modified sine wave shows some pauses before the phase shifting of the wave, i.e. unlike
a square it does not shift its phase abruptly from positive to negative, or unlike a sine

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wave, does not make a smooth transition from positive to negative, but takes brief pauses
and then shifts its phase.
Figure 2.2 showing the output waveform of a modified sine wave inverter
2.4 Safety of Inverter
The only input to the inverter subsystem is from the battery, the battery is being
charged from the power source (PHCN) through the charging subsystem through its
integrated system. Our key concerns regarding the power inverter system were as
follows:
i. Safety - because we are dealing with high currents, many safety concerns needed to be
accounted for.
ii. Output Waveform

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iii. Power Output needs to handle at least 2000W
iv. Efficiency generally there are a lot of losses associated with converting power. The
inverter will receive DC power from the battery, and convert it to usable DC and AC
outputs.
All other subsystems receive information from the output of the power inverter.
As such, the inverter is critical to the integrity of the entire system. Safety concerns must
be at the forefront of the circuit design. These concerns stem to the safety of the users, as
well as the circuitry itself.
We recognized this issue, and accounted for it with properly placed kill-switches
and fuses/circuit breakers. The circuit was designed so that if a power spike occurred, or
something malfunctioned, the key components of the system would be saved, and the
system would be shutdown.

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CHAPTER THREE
3.0 Methodology and Overall Design
The construction was done by following the under listed procedures; Firstly, two
sixteen IC socket were fixed on the Vero board to be used for panel construction. A 4.7k
resistor was connected from pin 1of the first IC socket and then taken to pin 16 of the
same socket. Two 0.1uf ceramic capacitors were connected in parallel and their joints are
linked between pin 5 and 7. Pin 4 is also linked with pin 5 and both are grounded.
Then 10k resistor is connected from pin 6 and then connected to another variable
10k resistor, the common path pin of this is linked with the second pin and the joint is
grounded, two 4.7k resistors are connected to pin 1 and 2 and both are linked with pin 8
which is grounded. After this, pin 12 and 13 are joined together and both are connected to
pin 15. This pin is then taken to the output pin of the used variable regulator LM7805, pin
10 is taken to the ground through a 4.7k resistor and also pin 9 is taken to the ground
through a 10uf capacitor.
A link is set between pin 14 of the first IC socket and pin 2 of the second IC
socket, another link is set between pin 11 of the first socket and pin 4 of the second
socket. These two links are both grounded through a 10k resistor, one for each link. Pin1
of the second IC is connected to pin 7 through a 10k resistor while another 10k resistor is
used to link pin 2 and pin 7 at the socket. Pin 8 and pin 12 of the same IC are also

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connected together with another 10k resistor while 10uf capacitor is connected from pin
10 to the second socket and then to ground.
A variable resistor is connected in such a way that its common pin is connected to
pin 10 of the IC and the other two pins are connected such that one pin is grounded at the
other end which receives the AC regulating signal from the control on the transformer to
provide AC regulation for the AC output. Four transistors are connected to the Vero
board such that the base of an NPN transistors are connected with the base of a PNP
transistor, the emitter of NPN transistor is connected with the collector of the PNP
transistor and these are taken to the positive pin of the used regulator.
The base link is taken to pin 1 of the second IC through a 10k resistor. This
process is repeated and it is connected to pin 3 of the second IC socket through another
10k resistor, then the collector of the NPN transistor and emitter of PNP transistor are
linked together for each transistor arrangement, and this is linked with a 1k resistor which
is looped with another 10k resistor that is grounded.
The joint between the 1k resistor and the 10k resistor is tapped out for each
transistor arrangement and each of these is taken to the gates of the MOSFET to be used
must have been arranged on the heat sink. A limiting resistor is connected to these gates
before they are connected to the joint point. The drains of the MOSFET are linked
together with considerations given to how they are joined to the oscillatory panel. Each of

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these is tapped out which will be joined to end to end terminal of the secondary side of
the transformer, while all the sources of the MOSFET are joined together to provide
negative terminal connection for the inverter.
3.1 Block diagram of the system
Fig. 3.1 Block diagram

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Circuit diagram of the system
Fig. 3.1 Circuit diagram
3.2 Components of an Inverter
One of the purposes of this chapter is to highlight the various components used in the
construction of the circuits that makes up the project as well as outlining whatever
calculation involved where necessary. The components making up the inverter include
relays, resistors, capacitors, transistors, voltage regulators, heat sink, MOSFETs, switch
and various ICs etc.

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Resistor
The resistor is the most widely used circuit element. It offer opposition or introduces
resistance to the flow of charges (electrons) or current in an electric circuit. They are
placed to regulate the flow of current and voltage drop in both electrical and electronic
circuits. In power circuits, they are used to reduce voltage by dissipating power.
Figure 3.2 (a)Symbol of a resistor (b)physical appearance of a resistor
Resistors are also characterized by how much power they can safely dissipate as well
as other parameters such as tolerance, noise, temperature co-efficient, voltage co-
efficient, stability with time and inductance.
Capacitor
The capacitor is another very important device that is essential in nearly every circuit
application. It is passive circuit element. It is a device capable of storing electrical energy
in the form of electrostatic energy. It consists of two plates separated by layer of
insulating medium called a dielectric.

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The strength of the dielectric determines the capacity of the energy stored in the
capacitor. The capacitance is the property of a capacitor to store electrical charges.
Capacitors come in various sizes and shapes, and are named according to the type of
insulation used. For instance, the ceramic capacitor used thin ceramic as its insulation,
and the oil capacitor uses oil as its insulation.
Fig. 3.3 (a) Symbol of a capacitor (b) physical appearance of capacitor
Diode
The diode is an electronic component which allows current to flow through it only
in one direction thereby opposing the flow of current in the opposite direction. Other
types of diodes used are Zener diode and light emitting diode.

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Figure 3.4 Symbol and physical appearance of a diode
Relay
An electromagnetic relay is basically a switch operated by a magnetic force. This
magnetic force is generated by flow of current through a coil in the relay. Current flowing
through the coil of the relay creates a magnetic field which attracts a level and changes
the switch contacts. The coil current can be on or off, so relays have two switch positions
and must have double throw (changeover) switch contacts.
Figure 3.5 Physical appearance of a relay

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A relay basically consists of four parts:
i. An electromagnetic made of a coil and a magnetic circuit
ii. A movable armature
iii. A set of contacts
iv. A frame to mount all these components.
Transistor
The transistor is the most important example of an ‘active’ component, a device that
can amplify, producing an output signal with more power in it than the input signal. The
additional signal comes from an external source of power.
In the inverter circuit, the transistor is used to generate oscillation signal
amplification of signal and to switch on/ off various circuits.
Fig.3.6 (a) Symbol of a transistor (b) Physical appearance of a transistor

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There are two types of standard transistors namely: the NPN and PNP transistors.
These transistors consist of two PN junctions formed by sandwiching either P-type or N-
type semi-conductors between a pair opposite types.
Metal Oxide Semi-Conductor Field Effect Transistor (MOSFET)
The MOSFET is a class of FET transistors. The FET as the name implies conduction
in a channel is controlled to the gate electrode. There are no forward-biased junctions, so
the gate draws no current.
The MOSFET is an important semi- conductor device and is widely used in many
circuit applications. In an inverter however, the MOSFETs are used as switching device
at the inverter output section.
The various terminal of MOSFET are;
i. Source: This is terminal which majority carried enter the bar. Since carrier come from it,
it is called the source.
ii. Drain: This is terminal through which majority carrier leave the bar i.e. they are drained
out from this terminal. The drain to source voltage V DS drives the drain current ID.
iii. Gate: These are two internally connected heavily doped impurity regions, which form
two P-N junctions. The gate - source voltage VGS reverse biases the gates.

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Figure 3.7 IRF3205 Physical appearance
The MOSFET is used in the inverter circuit as a switching device due to the
following reasons;
i. It can work on very small drive power
ii. Its efficiency is higher at the high frequency.
iii. The input impedance of MOSFET is very high, so it can work without DC
current.
iv. Switching time of the ordinary transistor gets affected by temperature, whereas
the temperature has very little effect on MOSFET device.
v. The ‘safe operating area’ of the MOSFET is larger than the bipolar transistor;
hence the MOSFET device does not get easily damaged.

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IRF 3205
The IRF3205 is N-channel MOSFET designed for high current switching
applications. Rugged EAS capability and ultra-low RDS (ON) is suitable for PWM,
load switching .
Features
i. VDS =55V; ID=105A@VGS=10V; RDS (ON) <6.0mΩ @ VGS=10V
ii. Ultra Low On-Resistance
iii. High UIS and UIS100% Test
Application
i. Hard Switched and High Frequency Circuits
ii. Uninterruptible Power Supply
Heat Sink
This is a metallic component that is used to conduct away heat which is generated
the MOSFET. It prevents the MOSFET from damage that may occur from overheating.

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Voltage Regulator
A voltage regulator has only three legs and appears to be a comparatively simple
device, but it is actually a very complex integrated circuit. A regulator converts varying
input voltage and produces a constant regulated output voltage. Voltage regulators are
available in a variety of outputs, basically 5volts, 9 volts and 12 volts. The last two digits
in the name indicate the output voltage.
Voltage regulators are very robust. They can withstand over-current draw due to
short circuits. In both cases, the regulator will shut down before damage occurs. The only
way to destroy a regulator is to apply reverse voltage to its input. This reversal of polarity
can destroy the regulator almost instantly. To avoid this possibility, diode protection of
the power supply is used.
Generally, the input voltage should be limited to 2 to 3 volts above the output
voltage. The LM7812 and LM7805 regulator is used for this project.
Figure 3.8 (a) LM7805 physical appearance (b) LM7805 circuit diagram

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Transformer
The transformer is a device that alternating current from one voltage level to
another. It has no rotating parts. It works on the principle of mutual induction.
Transformer needs two coils which is wound on a laminated core. These coils are called
primary coil and secondary coil. The coil to which the AC supply is provided is called
primary coil/winding while the coil in which the e.m.f is induced and from which the
output is taken is called secondary coil/winding. There is no direct electrical connection
between the primary and secondary coil in a transformer.
Figure 3.9(a) transformer circuit diagram (b ) transformer diagram showing coils
All transformers have the following essential elements; electrical windings
insulated from each other and from the core, a core, and insulating materials.

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E.M.F. EQUATION OF A TRANSFORMER
Let
N 1 = number of turns in primary
N 2 = number of turn in secondary
Øm = maximum flux in the core,
Wb = Bm x A
where;
Bm = maximum flux density in the core
A = Area of the core
f = frequency of A.C input, (in Hertz).
Therefore;
r.m.s value of e.m.f per turn = 1.11 x 4fØ max = 4.44fØ max volt
Hence, r.m.s value of induced e.m.f in the whole of the primary winding is
E1 = 4.44fØ max N1 …………………………………. (1)
r.m.s value of induced e.m.f in secondary winding is
E2 = 4.44fØmaxN2 ………………………………… (2)

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For an ideal transformer on no-load, V 1 = E1 and V 2 = E 2
Efficiency of a Transformer
The efficiency of a transformer at a particular level and power factor is defined as
the ratio of power output to power input. Therefore, efficiency can be calculated by
determining core losses from open circuit test and copper losses from short circuit test.
Losses in a Transformer
The major losses in a transformer are power losses. The various kinds of losses
are; core losses, copper losses, dielectric losses and stray losses.
Integrated Circuit (IC)
An integrated circuit as the name implies is a complete electronic circuit in which
both active and passive components are fabricated on extremely single chip of silicon.
Active components are those components which have the ability to produce gain e.g.
transistors, while passive components are those components which do not have the ability
to produce gain e.g. resistors, capacitor and inductors.
Therefore, the integrated circuit is a discrete circuit which is built by connecting
several components together. The integrated circuit is preferred in electrical/electronic
circuits because it does the work of the entire components that are composed on it, and is
handier and less bulky than using the components in it. In this project, we use SG3524IC.

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Figure 3.10 showing SG3524IC pin diagram
Function of SG3524 IC
This integrated circuit contains all the control circuitry for a regulating power
supply inverter. Included in the 16-pin dual-in-line package is the voltage reference, error
amplifier, oscillator, pulse width modulator, pulse steering flip-flop, dual alternating
output switches and current limiting and shut down circuitry. This IC is a very common
Integrated Circuit in MOSFET based inverter device.
3.3 Stages Involved in the Construction
MOSFET Stage
This stage consists of FET (Field Effect Transistor) which is arranged on the heat
sink to ensure even distribution of heat on the transistor. The MOSFET is connected such

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that its gate before they are connected to the joint output. The drain of the MOSFET is
linked together with consideration given to how they are joined to the oscillatory circuit.
Each of this is tapped out with which will be joined to the end of the low voltage
side of the transformer. All sources of the MOSFET are connected together and taken to
the negative terminal of the battery.
Figure 3.11 showing the MOSFET stage diagram
Oscillatory Stage
The oscillatory circuit is the stage of the inverter that produces frequency pulse
which gets to the gate of the MOSFET drive after amplification. IC SG3524 is used as
the oscillator of the inverter. The signal from pin 11 and pin 14 are connected to the

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second IC from where it is amplified and then taken to the MOSFET stage. The
MOSFET drive signal is amplified.
Figure 3.12 showing the oscillation stage diagram
Battery Stage
The battery is used to provide the required D.C to power the circuit, which voltage
level was ensured to be 12V. SG3524N is a fixed frequency pulse width modulation
voltage regulation control circuit. The regulator operates at the frequency that is
programmable by the timing resistor, and one timing capacitor.

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Figure 3.13 showing deep cycle battery diagram
Transformer stage
The transformer consists of small AC voltage which is received from the
MOSFET. It is transformed and stepped up to an appropriate value ranging from 220V to
240V depending on our desire which is varied from the 10k resistor to the IC SG3524.
The transformer high voltage side serves as the inverter output to the socket, it also
receives from power supply from PHCN and then used in charging the battery.

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Figure 3.14 showing the transformer stage diagram
3.4 How to choose the best inverter battery
Nowadays, it is almost unimaginable to survive without power supply in our
homes or workplaces. However, the moment power supply to our appliances and other
gadgets that makes our everyday lives a lot easier and relaxed goes off, our lives becomes
boring. Such situation leaves us really bothered unless there is an inverter with a
powerful inverter battery.
Here is a list of some most important things to consider when choosing the best
inverter battery is as follows;
i. Understand the power requirement
ii. Be aware of the inverter battery size that you require.
iii. Find the VA rating of the inverter you require.
iv. Consider the bigger appliances

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CHAPTER 4
4.0 Test, Observation and Results
The design of the project, construction of a 2KVA Inverter, was followed by its
construction. Many considerations were put in place in form of procedures and
instructions, which led to the successful completion of the project. The project is
constructed on a Vero board, in which the size of the main panel board was used to
choose the dimension of the casing used.
4.1 Testing
Purpose of Testing
Testing of components is important during construction to ensure that the works
compiled together are perfect with their specifications. Testing is also essential during
operation and after the completion of the construction made to determine the longevity of
the inverter in order to detect common fault that may arise. There are sequences of test
needed to undergo for any successful project.
i. Component testing
ii. System testing
Component Testing
Every component was tested singly to ensure that each was in good condition
before assembling on the board. The major test carried out on these components was

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continuity testing done with the use of multi-meter like transistors. The test made on
transistors was used to test each terminal of a transistor. Polarity testing was also
performed on some components like diode, capacitors, etc.
System Testing
This involves the testing of the entire circuitry and thus, examine it for errors like
short-circuits, lead flux, joining unwanted links. Proper insertion of IC pin layout and
also checking if ICs of these pin number are slotted in their proper base. After checking,
cross check again before powering the system.
4.2 Observation
It was observed that components used for the construction are not predominantly
static, electronic data book played a major role in identifying other available component
in the absence of one.
The first section that was carried out was the MOSFET arrangement which was
tested and was found working. The second was the oscillating circuit while the third is
the charging circuit.
All the circuits were tested and found to be working. The MOSFET arrangement
later developed some problems likewise the oscillating circuit, the problems were later
resolved after consulting the supervisor and our senior colleagues.

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The MOSFETS stage
The MOSFET used for this project is IRF3205 and the drain current rating of the
MOSFET is 100A (at 250C). By considering increase in temperature (let say 1000C), the
drain current rating is taken as 105A. This is because as the temperature increases, the
drain current also increases. Therefore, the drain current is taken as 105A.
Inverter power rating = 2KVA
Input voltage = 12V
Therefore, in order to determining the current that will flow in the input circuit:
P = IV ∴ I =
𝑃
𝑉
Therefore, I = 2000VA
12V
Therefore, I = 167A
Oscillator Stage
The frequency of oscillation is set to 50Hz. This is determined by the values of
the charging resistor RA and RB, capacitor C1 and discharging resistor RB. To obtain
approximately 50% duty cycle, the value of RA is set to 1kΩ.

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Figure 4.1 showing the circuit diagram of Astable Multi-vibrator Circuit using NE555IC
The Transformer stage
This is the final and output section of the inverter circuit is always step up
transformer in order to increase the ac voltage generated. The transformer determines the
power of the inverter.
For our project (i.e. 2KVA inverter) a 12V/220V step up center- tap transformer
was used.
4.3 Results
The power rating of the inverter is 2KVA
Therefore, at the input (primary side)

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V = 12V, P = 2000VA
Therefore, I =
𝑃
𝑉
=
2000𝑉𝐴
12𝑉
I = 167A
At the output (secondary side)
V = 220V
P = 2000VA
I =
𝑃
𝑉
=
2000𝑉𝐴
220𝑉
I = 9.09A
Inverter Output test
After all stages had been coupled, the output of the inverter was tested. This was done
by first connecting a voltmeter to the output terminal of the inverter to test the output
voltage. A 200W bulb was then connected to the output terminal of the inverter to see if
the bulb will bring light at a desired brightness.
4.4 Casing and Packaging
A new casing was purchased, and also a cover board in order to produce a neat and
durable production.

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We ensured that the casing purchased contains a ground wire to give it a proper earthing.
Figure 4.2 Casing of the inverter
4.5 Assembling of Section
The sections were assembled together in the casing properly and carefully to avoid
destroying the circuit arrangements. We also ensured that the assembling does not create
avenue or chance for short circuit and so, we connect the circuit to a ground wire.
Assembling Instruction
It is often easier while assembling the components on the board to erect them
according to their height. That is, the lowest components first, usually the resistor and
other tiny ones while others with higher height follow. Care was taken in getting the
polarity of components like diode, electrolytic capacitor etc., before they were being

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soldered on the panel. Also, the biasing of the transistor was vividly ascertained before
permanent soldering on the board was carried out.
The use of IC socket was employed to avoid any damages that might result from
excessive heat while soldering the IC. The pin configuration of the IC used and its
connectivity with other components on the board were strictly adhered to as shown on the
design work before the socket was permanently soldered. In fact, IC socket was the first
item on the board while other components were placed around it.
4.6 Cost Analysis
Table 4.1 below shows the cost expenses of the project;
S/N DESCRIPTION PRICE
1. Components 10,900
2. Battery 45,000
3. Transportation 4,500
4. Transformer purchase 5,500
5. Casing expenses 6,300
6. Miscellaneous
expenses
2500
TOTAL 79,200

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4.7 Troubleshooting/ Fault tracing
This is a way of identifying, tracing and locating fault for immediate rectification.
Problems may result from inadequate soldering and most likely be the reason why the
circuit may not work. Other reasons may be due to electrical contact between the leads of
the component, excessive voltage supply to the circuit (in case of using an adapter) etc.
Soldered joints were carefully checked under bright light to ensure adequacy. All
components were also checked to make sure they were in their correct position on the
board. The voltmeter was used to check voltage at various points on the circuit was also
embraced to follow the connection tract.
4.8 Maintenance and Repair
Maintenance and repair of an inverter is tedious to carry out. It involves the
technical know-how of an individual to put together his garnered experiences to properly
handle the repair of an inverter. Nevertheless, some routine maintenance checks may be
carried out for precautionary and safety measures. Some of this maintenance checks are:
i. Check for proper ventilation in the inverter which is provided by the cooling fan.
ii. Ensure proper charging of the battery to avoid overcharge of battery which may cause
damage to the battery.
iii. Battery terminal should be checked regularly to ensure proper supply to the inverter.

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Other maintenance and repair can also be carried out at the different stages of the inverter
as this helps to detect faults that may arise and for it to be rectified immediately.

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CHAPTER FIVE
5.0 Conclusion
This project has given us better understanding of the practical aspect of our course
of study (Electrical/Electronic Engineering), it has also enable us to acquire more
practical skill and knowledge. The completion of this project of construction of a 2KVA
inverter with 12V DC dry cell battery has given expected results after different tests were
carried out on each stage which gave durable and accurate results.
The proper running of this inverter is a clear indication that the set aim and
objectives have been achieved. The construction is based on the theoretical knowledge
gained so far during our lecture times. It is constructed with considerable cost, available
and reliable components rather than the more exorbitant unavailable ones.
The practical knowledge of the multi–purpose use of SG3524 IC, MOSFETs,
relay etc makes the project interesting, tasking and educating.
5.1 Recommendations
Logically, irrespective of how good a design might be, there is always room for
improvement. By so doing, the following recommendations could be taken into
consideration for more effective and useful inverter.

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i. Competent personnel should be consulted in case of any damage to the unit and
every source of power supply should be disconnected from the inverter before
removing the cover.
ii. Soldering of components should take a network system in order to minimize heat to
the components.
iii. On no occasion should the inverter be loaded above 80% of its maximum capacity.
It’s an international advice.
iv. Student should be exposed to more practical works so that they would be able to
construct all practical works themselves.
v. Government at various levels should encourage engineering practice by financing
and training of engineering within and outside the country for the benefit of the
students and the nation at large.

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REFERENCES
Team Not Platypus (May 12, 2010)
‘DC-AC/DC Power Inverter’
Authors: Matthew Brown, Henry Godman, John Martinez, Dylan Paiton and
Matthew Paiz
Abdulwahab Olanrewaju Issa (2016)
‘Practical guides to project writing for students in Polytechnics, Colleges and
Universities’
Department of Library and Information Science,
The Federal Polytechnic, Offa, Kwara state.
BL Theraja (2003)
Principles of Electronics
Kwaha, B. J., Iluonu, J and Danladi, C. (June 2004)
‘The design and construction of a 2kVA H-bridge inverter’
Department of Physics, University of Jos, Jos.
https://www.exidecare.com/blog/battery-care/how-to-choose-the-best-inverter-battery

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Student final year project (April 2014)
‘Construction of 3KVA DC/AC Inverter with Deep cycle battery’
Authors: Azeez Akande, Olaniyan Kunle, Bello Oladayo, Ajimotokin Festus,
Npue Collins
Department of Electrical/ Electronics Engineering,
Federal Polytechnic, Ede, Osun state.
www.myprojectcircuit.com/2kva-inverter.html