The construction of a 2kva automatic
voltage regulator (avr)
BY
-------------------------------------------------------
A PROJECT REPORT PRESENTED TO THE DEPARTMENTOF
ELECRTICAL/ELECTRONICS ENGINEERING,
SCHOOL OF ENGINEERING TECHNOLOGY
----------------------------------------------IN PARTIAL FULFILLMENT OF THE REQUIREMENTS
FOR THE AWARD OF ---------- IN ELECTRICAL/
ELECTRONICS ENGINEERING
AUGUST -------
CERTIFICATION PAGE
This project was built and presented to the Department
of Electrical /Electronics Engineering, -----------It was duly approved, supervised and certified by the
Authorities of the department as having conformed with
the necessary requirements.
…………………………….…
……………………………
Engr.----------(Project Supervisor)
…………………………….…
……………………………
Engr. ----------(Project Coordinator)
…………………………….…
……………………………
Engr. ---------------------(HOD EEE)
…………………………….…
Engr. DR. -----------------(External examiner)
Date
Date
Date
……………………….
Date
ABSTRACT
The AVR is automatic voltage regulator and it is a
device which is used to regulate or stabilize electrical
power supply for electrical or electronic appliances
In this project, therefore, we are interested in the
construction of this all important device. Furthermore, we
shall discuss the techniques, processes, switching stages
and then the working principle of the automatic voltage
regulator
Chapter one of this project dwells on the
introduction of the project topic. It also talks about the
objectives of the project, bringing to mind what we
intend to achieve at the end
Chapter two of the project reviews the research
works that have been carried out by some other people
in this study area. It also discusses on some of the
components used in this project
Chapter three gives a detailed account of the basic
construction and the operation of the AVR. It also
highlights on some other components used, discussing
their working principles using both the circuit and block
diagrams
Chapter four of this project draws the conclusion
and consequently gives the recommendation on how to
better the operation of the AVR. It also includes the
references and articles consulted in the course of this
project.
ACKNOWLEDGMENT
We wish to express our sincere gratitude to all the
lecturers in the department of Electrical/Electronics
Engineering for their sound academic support in the
course of our programme in this institution.
Our special gratitude goes to our Project supervisor,
Engr. -------- for his tutelage, fatherly advice and special
guide towards the achievement of this project.
Finally, we appreciate our numerous friends and
well-wishers who in one way or the other, contributed to
the success of this project.
We say may the good Lord bless us all-Amen
DEDICATION
This Project report is dedicated to Almighty God, for His
infinite mercy, guidance and protection before, during
and after the execution of our project.
TABLE OF CONTENTS
Certification page
i
Abstract
ii
Acknowledgement
iii
Dedication
iv
Table of content
v-vi
CHAPTER ONE
1.1 Introduction to automatic voltage regulator
1.2 Objectives of the project
1-3
3-4
CHAPTER TWO
2.0 Literature review
5-7
2.1 Some of the components used
8
2.2 Resistors
8-9
2.3 Capacitors
10
2.4 Transistors
11-12
2.5 Relays
13-14
CHAPTER THREE
3.0 Basic construction and operation of the automatic
Voltage Regulator AVR
3.1 Components
15
15
3.2 Transformers
15-18
Circuit diagram of the AVR
19
3.3 The working principle
19-21
3.4 The main function of the AVR
23-25
3.5 The need for voltage regulation/stabilization
25-26
CHAPTER FOUR
4.0 Conclusion and recommendation
4.1 Conclusion
27
2728
4.2 The importance of voltage Regulation
28-30
4.3 Recommendation
30
Reference
31
CHAPTER ONE
1.0 INTRODUCTION
TO
AUTOMATIC
VOLTAGE
REGULATORS.
Automatic voltage regulators (AVR) in power supply unit
is a device
which
is used to regulate
electrical power supply for
electrical
or
or
stabilize
electronic
appliances. This device helps automatically to keep the
voltage level from the public power supply system
constant. In other words, the minimum
ranges
and maximum
of voltage are maintained in order to achieve a
constant output
of 220V.
These devices also
serve as
a protective device
for appliances connected directly to it, while the AVR is
connected directly to the public supply. The protective
system in AVR either regulate or stabilize it to 220V
output for the safety of our appliances or the fuse in
the AVR will rupture by excess current of the surge and
thereby cut-off the incoming power supply.
The
stabilization and regulation
through the control circuit which
is achieved
include relays and
other components
of
various
voltages from the
secondary winding of the auto-transformer used in this
project work.
This control circuitry does the work of cut and boost
in the case of higher and lower voltage respectively. If
the supply voltage drops below 220V down to 180V,the
primary control does the work of the boost which brings
the output
to normal , while
increases beyond
220V up to
when the
260V ( which
voltage
is not
ideal), it does the work of cut. The coils of the relay are
triggered by the 11.5V D.C from the last stage of the
operational
Amplification.
By
this
arrangement,
an
improved automatic voltage regulation is achieved and,
is hereby presented in this project.
Different techniques have been employed in the
design of AVR circuits in recent times but, in the design
and
construction
of this particular
voltage, excess current
type, high rise
due to dangerous condition
externally like lightening effect which may appear on
the
power supply lines were effectively isolated. The
system
chips
likewise
and
fragile
devices were protected
low voltage fluctuations make-brake power
supply from public power supply were taken good care
of in this AVR construction.
1.2 OBJECTIVE OF THIS PROJECT
The automatic voltage regulator of rating 2KVA is a
natural
choice
for
remote
control
device
consistent voltage level fluctuation of our
for
the
power supply
system. Therefore, we bear the following in mind as our
objective while carrying out this project;
1).
To fully understand
controlling
the automatic means of
and regulating the system, Its practices,
design, construction, operation and application in public
electric power system engineering
2). to test the electric power behavior of systems or
appliances connected to AVR. Also
to perform both
practices network computers, televisions, amplifier sets
and other sensitive devices intended to be protected
from direct connection to public electric power supply.
3). to practically engage in and fully understand the AVR
operational modes and technology or configuration in
electrical design and construction
4). To enhance
technology
power regulation
and stabilization
via automatic voltage regulation for our
electrical and electronics appliances
due to voltage
variation and, incessant power –fluctuations.
CHAPTER TWO
2.0 LITERATURE REVIEW
in an attempt
to
achieve
stability
voltage
and
consequently have a steady output, many researchers
have over the
years
carried
out detailed
and
comprehensive researches to fathom ways of achieving
this purpose. Sequel to the fact that, the power system
is characterized by strong-linearity, fluctuations, hybrid
system of dynamics etc. hence a review of these
researches becomes imperative.
According to V.K Mehta and Rohit Mehta (principle of
Power system,
2004, 2nd
edition), they
opined
that
voltage regulation is very important in order to avoid
or reduce the effect of fluctuations in the system. This
they said
devices
can be
achieved using
and switches which
vary the
semiconductor
rams voltage
impressed across the load.
In a journal released by Larsson . M. Hill in 200, D.H.
Hill and Wang Hill in 1996 respectively, they believed
that
voltage control and regulation
are indispensable
factor in power system and , thus aims at a mid or long
term voltage quality maintenance of power systems in
the
presence
of
load
and
transmission
line
disturbances.
According
to
a
research
work on AVR by Ogbekhilu
Jonathan (MIEEE), 2006 he stated “when variation of
voltage
are too wide at the point of generation or
utilization, there will be erratic operations of the entire
system, that of the consumer inclusive”. To protect the
consumer’s interest, IEEE regulation has stipulated a
maximum voltage drop of 5% of the detailed voltage
at the consumers terminals.
B. W. Williams , power electronics , 2 nd edition of 1987,
in his work stated emphatically that, Automatic voltage
regulators have
incorporate
a constant voltage a.c supply and
semiconductor
switches
in its operation.
He continued further saying that these regulation fall
into
since
the category of naturally commutating converters
their
thyristor
switch
are commuted
by the
alternating
supply.
He
termed
this
“the
line
commutation “
The regulator output current
he said, supply
current which may be discontinues or non- sinusoidal
and as a consequent input power factor corrections
and harmonics reduction are usually necessary.
From the forgoing, it is obvious that much have
been
done in
comparative
designs and construction
short time and various
of system
with improved
mode of operations have emerged in the process. My
inference therefore is drawn from the fact that, these
researches have a gone a long way to prove that the
automatic voltage regulator
is indispensable
in
achieving the stability of power systems.
2.1 SOME OF THE COMPONENTS USED INCLUDE;
Components:
These
are
electrical
or
electronic
materials or devices which can be discrete or nondiscrete in nature. They are used to form the basic
skeleton or structure of any workable circuit or device in
an electrical or electronic appliances or system. In this
project, the construction of a 2kva automatic voltage
regulator,
some
of
the
components
used
in
the
circulatory are highlighted and, their function explained
in detail. They include Resistor, Transistor, and Relays,
OP AMP (comparative transformer and, Rectifier circuit
comprised of diodes.
2. 2
Resistors:
this
is an
electronic component
which offers opposition to the flow of current
electric
or
electronic
circuits
depending
on
in an
the
resistance value. In this project, two kinds of resistors
were used. Namely, variable
(preset /potentiometer)
and ceramic or linear resistor
The variable
resistor consists of a track of
resistance materials to which
a movable wiper makes a
contact. They are mainly used for control purpose as in
the automatic voltage regulator (AVR) circuit. Also they
are preset in nature, using an insulator screw driver, they
can be varied
i.e. their resistance value can be varied.
Usually
have
they
three
pins
or
logs
which
are
conducting.
The ceramic resistors are the type of resistor that
is fixed in value. Their values cannot be varied. Usually
they posses’ two pins or logs which are their contact
points. Their insulation materials are quite different from
the one of the variable resistor
The use and range of resistors depend on the
ratings mixed with a binder and fixed in an oven to
produce a hard rigid shape. We used mainly the ceramic
type of 5k-330 ranges in this project is order to achieve
the objective of the project.
2.3
Capacitor: They essentially
consists of two
conducting surface separated by a layer of insulating
medium known as dielectric , which distinguished one
type of capacitor from the other.
The conducting surface may be in the form of
either circular or rectangular shape. Its main functions in
the circulatory are store charges and also, smoothen in
the process of rectification. Also, it helps to filter off the
ripples or the pulsating D.C voltage can also be used as
coupling and decoupling device.
Capacitor are various kinds namely- electrolytic
capacitor, paper capacitor, ceramic and the variable
types.
While
the electrolytic
negative
terminals
type
has both
dearly marked
positive
and
out in the
component, the ceramic and paper type do not have
the terminals spelt out.
2.4 Transistor
These are discrete or series conductor material which
has two back to back P-N junction manufactured in a
single
piece
of
a
semiconductor
crystal.
This
configuration gives rise to three regions called emitter,
base and the collector . also it is
sandwich
referred
to as a
of one type of semiconductor materials
between two layers and the two semiconductor junction
are emitter –base(E/B ) or collector base (C/B) junction.
Its main function in this construction work is to act as
a switching device.
Considering the above qualities of the
transistor,
we have the PNP and NPN types the lather being used
in this Automatic voltage regulator circuit. The PNP type
is gotten by
sandwiching a layer of N-type materials
between two sandwiching a layer of P- type material
between n two layers of N-type materials.
The arrow head on the emitter of PNP type points
inward, which indicated the convectional direction of
current flow from
emitter is positive
emitter to base meaning
with respect
to the
that, the
base. The
emitter is more doped than any of the other regions
because it supplied the majority charge carriers to the
base. (These are holes and electrons)
The
base forms the middle
section
of the
transistor and is lightly doped more than the collector
region for it has to the physically layer than the emitter
region for it has to dissipate much greater power and it
collects majority charge carriers coming from
the
emitter and passing through the base
RB
RC
1.0k
1.0k
Q1
Vb
2N1711
Vc e
Vc
RE
Ve
1.0k
2.5 Relays
These are switching
achieving
devices
or components used in
particular timing and monitoring
(mechanism
) or
trigging
technique
requirements
in an
electronic or electrical circuit, it has two terminals that
are connected
oriented
to coils of the
(about 12/26 volt D.C ) one A.C center tap
(that can handle
tapping
relay which are D.C
up to
(one of then
220V A.C ) the
other two
normally close and the
other
normally open
with the
automatic
voltage regulator
(AVR) circuit for the project
The relays which are three in number operate in
such
away
that they are switched
individually
or
differently (depending on the voltage level and voltage
requirement
from the
circulatory) through
respective coils . When a D. C voltage of about
their
16V is
applied to the two coils or winding terminals of the relay,
making the normally closed terminals
open. The
of the A.C volt
normally open terminal of the A.C volt will
close in contact with the A.C voltage output for the
circuit
from the
circuit do not
auto- transformer
trigger
on the
the relays in the
same a time but
are
triggered individually as required by the voltage supply
behaviour either it is increasing, decreasing or stable as
the case may be.
CHAPTER THREE
BASIC CONSTRUCTION AND OPERATION OF THE
AUTOMATIC VOLTAGE REGULATOR (AVR)
The basic
components
that
the
have are the operational Amplifier
voltage regulation
(OP AMP) and the
exclusive OR Gate logical IC, the components
are
being controlled by other network to achieve its main
and
deserved
operation. The automatic voltage
regulator (AVR) could be
said to be made up of the
input, central and output sections. It is the central
section is what signals the output to vary from input and
be stabilized. It
regulation
should be
noted
that the
voltage
is the ratio of the difference between the
full had voltage and the no-load
voltage over the
voltage of full load.
Mathematically,
Voltage regulation = voltage no-load-voltage of full load
Voltage of rated load.
From the foregoing , regulation thus implied the
ability to maintain voltage a constant regardless of the
variation
in the input, following are the components
used.
Components of the AVR
Auto – transformer, relays, Diode rectifier, Capacitor,
Resistor and variable Resistor, 12V regulator, Operational
Amplifier.
3.2 THE AUTO TRANSFORMER.
260V
220V
240V
The transformer used in the construction is an auto
220V
transformer. It does the work of stepping up or stepping
down voltage. Transformer
internally
to be
mutual
(two
physical
connection
0V
or
either
200V
are usually connected
180V
as an auto
(one coil) or12 a
more coils) in which
between
these
them.
The
is no
0V
auto
transformer has one straight coil for both the primary
and secondary. The required
voltage are drawn
after
getting the number of turns that is required to give the
exact voltage required, depending
on the quantity of
the lamination of the soft core, a voltage per turn of
0.4 was used
To obtain the number of lines that will give the 15V,
the following calculation was done
N= V
e/t
where N= number of lines
V= voltage
e/t= a constant in this transformer
= 15 = 37.5lines
0.4
Hence, the number of turns used is 38 turns in order to
achieve efficiency.
THE RELAYS
K1
NC
K
NO
1mH 1 
The relay
used in this
mechanical switch
current
construction
is an
electro-
which turn ON and OFF electrical
in a circuit. It is a is simplified mechanical
switch. It consists of a solenoid that pulls a lever by
magnetic attraction when there is an excitation in the
coil. This pull of the common
causes
the common
to be
towards the solenoid
disconnected
from the
normally closed to be normally open (NO). Thus , there
is flow of electric current through the common (pin3), it
goes to NC (pin4). But this causes an open circuit (off)
in pin 4 but the pin 3 is attracted to make contact with
12 V
2200uF-POL
3
2
1
pin 5. so , the current will flow out through pin 5 while
D2
VCC
D1
R9
the amount of C1
input voltage is drive the relay may be
X
12V d.c
R10
12V ac.c
10k
4
so small (about 12V), the relay can contact
VCC very high
Y
U1
VCC
U7
voltage with
tremendous
amount of power.
R1
5K _LIN
Key = A 50%
R2
10K _LIN
Key = A
3N246
COMPARATOR_VIRTUAL
U2
CIRCUIT
U3
COMPARATOR_VIRTUAL
50%
U5A
4070BP_5V
COMPARATOR_VIRTUAL
U4
U5C
4070BP_5V
R4 50%
COMPARATOR_VIRTUAL
U6
5K _LIN
Key = A
U5D
4070BP_5V
5K _LIN
Key = A
R11
5K _LIN
Key = A
50%
K1
2
U8
K
2N1711
Q2
OF AVR
EDR201A12
K2
2
U9
K
33.0K
2N1711
50%
R3
Q1
33.0K
U5B
R6
DIAGRAM
4070BP_5V
5K _LIN
Key = A
R5
R7
Q3
EDR201A12
180k

XMM3
K3
R13
2
U10
K
33.0K
2N1711
R8
Q4
EDR201A12
2
U11
K4
LED2
K
33.0K
2N1711
R12
EDR201A12
2
LED1
12V a.c
XMM2
COMPARATOR_VIRTUAL
L
180k
50%
N
Out put
220V
Input
mains
X
Y
3.3 THE WORKING PRINCIPLE
At the input section, 220V a.c mains is applied, a 12V
a.c is tapped and fed to a rectifier circuit which converts
the a.c voltage to a d.c voltage. The 25V capacitor filters
off the ripples of A.C and thus, achieve a pure d.c
which is then applied to the voltage regulator circuit as
Vcc. The voltage regulator L78M12 regulates the output
voltage to ensure stability at 12Vd.c
The comparator (OP-AMP) compares the sensing
voltage
(preset) to the reference voltage and amplifies
the difference
(error) to provide a controlling signal for
the power devices (exclusive OR gate and transistor)
The 330Ω resistor limits the over voltage that might
pass into the transistor.
The switch (transistor) which is (9014 power transistor
switches between the difference voltage tapping of
the auto-transformer thus causing the relays to sense
the
signal and thus, makes and breaks at different
voltage tapping of the transformer. If a high voltage is
sensed by the relay, it causes the relay at the high
voltage to be triggered. Also, if a low voltage is sensed,
the relay at the low voltage is triggered. This ensures
that output is maintained at a constant steady value. The
output voltage is measured by the voltmeter and
displays it.
22
Voltage
sensing
FIG;THE BLOCK DIAGRAM OF AVR.
Low HZ
detection
Synchronizing
Circuit
Hand trimmer
AMP
Low
pass
filter
Supervision
Power
supply
Reference
voltage
Potential
Divider
&
Rectifier
Generato
r
Ramp
Generator
Level
detector
& drives
Power
control
device
Stability
circuit
3.4 THE MAIN FUNCTIONS OF THE AVR
POTENTIAL
DIVIDER
AND
RECTIFIER:
takes
a
proportion of the generator output voltage and attenuate
it. This input chain of resistors includes the range
potentiometer and hand trimmer which adjust the
generator voltage. a rectifier converts convert the A.C
into d.c for further processing .
THE AMPLIFIER
(AMP) compares the sensing voltage
to the reference voltage and amplifiers the difference
(error) to provide a controlling signal for the power
devices.
The Ramp generator and level detector and driver
infinitely control the conduction period of the power
control/ devices and hence provides the excitation
system
with
the
required
power
to
maintain
the
generator voltage within specified limits.
THE STABILITY CIRCUIT: provides adjustable negative
a.c feedback to ensure good steady state and transient
performance of the control system.
THE LOW HZ DETECTOR : Measures the period of each
electrical cycle an causes the reference voltage to be
reduced
approximately linearly
with speed
below
a
pre-settable threshold .
a light emitting
diode gives indication of under speed
running.
THE SYNCHRONIZING CIRCUIT is used to keep the
Ramp generator and low HZ detector locked to the
generator waveform period
THE LOW PASS FILTER PREVENTS distorted waveform
affecting the operation of the AVR
POWER CONTROL DEVICES: vary the amount of
exciter field current in response to the error
signal
produce by the amplifier.
SUPPRESSION COMPONENT: are included to prevent
sub-cycle
voltage
components
spikes
and also
damaging
to reduce
the
AVR
the amount of
conducted noise on the generator terminals.
THE POWER SUPPLY PROVIDES: the required voltage
for the AVR circulatory.
FEEDBACK
260V
240V
RECTIFIER
COMPARATOR
220V
SWITCHING
RELAYS
200V
180V
12V
0V
FIG: BLOCK DIAGRAM OF AVR.
3.5 The Need for voltage regulation /stabilization
1). lighting: voltage variation affects lamps. this is
because lamp characteristics are sensitive to charge in
voltage.
for
incandescent
example,
when
the
lamp decreases by
voltage
of
an
6% of the rated
voltage, the lamination power decrease by 20%. also, if
the supply voltage is
6% above
“life” of the lamp is reduced by
deterioration of the filament.
the rated value, the
50% due to rapid
2). It brings about stability and hence reduces fluctuation
in the power system.
3).
In
distribution
transformers,
too
wide
voltage
variation causes excessive heating of the distribution
transformer and, this reduces their performance and
efficiency.
CHAPTER FOUR
4.0 CONCLUSION AND RECOMMENDATION
4.1 CONCLUSION
The importance of power supply in our everyday life
cannot
a
be
over-emphasized
since
most
of
our
economic activities are dependent on power supply. It is
certain that all the electrical and electronic appliances
used in industries, institution, homes and offices will be
at its best operation when
the power supply is made
constant and optimum but the reverse is the case if
otherwise.
One of the short comings militating against the
ultimate
or
required
output
of
any
appliance
is
fluctuation in power supply, not only does this situation
affect the systems output but also
it is possible
to
introduce fault into the system.
Consequently, damage to some of the delicate
components
components
of
the
system
operated
may
beyond
occur,
their
especially
capacity.
In
otherwords,
constant
output
of
power
supply
is
necessary for effective performance of any electronic
system.
The automatic voltage regulator (AVR) is one of
those devices used to maintain constant level of power
voltage in a power system. The AVR in its operation is
automatic and is very sensitive to variations in voltage
level and stabilizes its output.
Hence, THE IMPORTANCE OF VOLTAGE REGULATION
ARE:
a). Lighting : the lamp characteristics are very sensitive
to changes in voltage. For example, if the supply voltage
to an incandescent lamp decreases by 6% of the rated
value, then illuminating power may decrease by 20%.
Consequently, if the supply is 6% above the rated value,
the life of the lamp may be reduced by 50% due to rapid
deterioration of the filament
b). In case of power load consisting of induction motors,
the voltage variations may cause erratic operations. If
the supply
voltage is above
the normal,
the
motor
may operate with
a saturated
magnetic
circuit, with
consequent large magnetizing current, heating and low
power factor. In the other hand, if the voltage is too low,
it
will
reduce
the
starting
torque
of
the
motor
considerably.
c). Too wide variation of voltage cause excessive heating
of distribution transformers. This may reduce their rating
to a considerably extent.
It is thus very clear from the discussions that
voltage variation in power system must be kept to a
minimum level in order to deliver good service to the
consumers via voltage stabilization techniques and
regulation.
Also, the AVR can be seen as a protective device
to electrical and electronic appliances because of the
auto transformer
relays and other control devices like
transistors used in this project. Going by it’s name and
mode of operation, the AVR can handle different voltage
levels with the range of its control and optimize them to
be usable to the appliances.
4.2 RECOMMENDATION
In the construction of this automatic voltage Regulator
which
is geared
ideology,
towards understanding
knowledge,
theories
operations of the AVR, we,
,
the basic
principles
having
and
gone through
various procedures involved in the construction of such
an important
adherence
equipment, recommend
to the laid
down
that
strict
steps and operational
conditions discussed in this project.
The construction
regulator is interesting
constraints
we
of
2000VA automatic voltage
and educating
encountered
which
albeit
took
us
some
into
advancement in electrical and electronics power and
voltage regulation.
REFERENCES
(1)
V.R Mehta and Rohit Mehta. Principle of power
system engineering, 2nd
Edition. publisher S.
chan D and company ltd
(2)
Www. Googel.com (internet)
(3)
penfold Robert: Everyday electronics, June1980,
3rd edition by S.K publishers, U.K
(4)
(5)
Www. ieee. Com
Theraja
Technology
B. L and
Theraja A.K: Electrical
(2004) 2nd edition
by S. Chan D
publishers
(6)
Amadi
J.N: Electronic design and Drafting
for
project Building (2002)
(7)
Journal of Larsson Hill, D.H Hill of 2002 and 1996
respectively, of the University of Cambodia.
(8)
http://www.zju.Edu.injzuz.