DESIGN AND CONSTRUCTION OF
AUTOMATIC CHANGE-OVER FOR THREE
PHASES
ABSTRACT
The main aim of any electric power supply in the world is to
provide uninterrupted power supply at all times to all its consumers.
Although in developing countries, the electric power generated to
meet the demands of the growing consumers of electricity is
insufficient hence instability and outage.
Power instability or
outage in general does not promote development in the public and
private sector. The inventors do not feel secure to come into a
country with constant or frequent power failure. These limit the
development of industries. In addition, there are processes that
cannot be interrupted because of their importance. For instance,
surgery operation in hospitals, transfer of money between bank and
lots more. Power instability and outage in developing countries
(Nigeria) creates a need for alternative source of power to backup
the main supply. Automatic changeover switches find a wide
application scope wherever the reliability of electric supply from the
utilities is low and it is used in lighting motor circuits wherever
continuity of supply is necessary. For switching to an alternative
source from main supply and vice versa. This project is a design of an
automatic changeover switch this means that when there is any
mains failure, the automatic changeover switch will change to an
alternative power supply (GENERATOR) and back to the main supply
when it is restored. The purpose of this project is to maintain
constant supply to the main circuit that is being supplied by making
up for the time delay that usually accompanies the manual switching
from one source to another. The design comprises of the power
connection circuit and control connection circuit. The main
components to be used include contactor, relay, timers, rectifiere.t.c.
i
TABLE OF CONTENTS
Title Page
i
Certification
ii
Acknowledgements
iii
Abstract
iv
Table of Contents
v
CHAPTER ONE
1.1
Introduction
1
1.2
Aim and Objective of the Project
3
1.3
Scope of the Project
3
CHAPTER TWO
2.1
Literature Review
5
2.2
Manual Change-over Switch
5
2.3
Automatic Change-over Switch
6
2.4
Related Work
10
2.5
Reasons for Automatic Change-over Switch
16
2.6
Problems of Automatic Change-over Switch
17
ii
CHAPTER THREE
3.1
Methodology (Material and Methods)
18
3.2
Circuit Conductor
18
3.3
Circuit Breaker
19
3.4
Reset Timer
20
3.5
Contactor
21
3.6
Operation of Timer Delay
24
3.7
Principle of Operation
25
CHAPTER FOUR
4.0
Construction
29
4.1
List of Component Used
29
4.2
Vero Board
29
4.3
Bread Board
30
4.4
Soldering Iron
33
4.5.1 Testing, Maintenance and Discussion
36
4.5.2 Polarity Test
36
4.5.3 Insulation Resistance Test between the Live and Neutral
Conductors
37
4.5.4 Earthling Test
37
iii
4.6
Maintenance of Contactor and Installation
37
CHAPTER FIVE
5.1
Conclusion
39
5.2
Recommendation
39
References
40
Bill of Engineering Measurement and Evaluation (BEME)
41
iv
CHAPTER ONE
1.1 INTRODUCTION
Power instability in developing countries creates a need for
automation of electrical power generation or alternative sources of
power to back-up the utility supply. This automation is requiring as the
rate of power outages become predominantly high. Research in the field
of electrical electronics engineering has led to the tremendous discovers
and inventions especially in the area of automation and power control.
These invention have been useful in solving the over-in (Mustapha,
2006).
Creating problem posed by power generation, distribution and
control, which has been a cause of concern especially in the third world
countries (developing countries) like Nigeria. Most industrial and
commercial process is dependents on electric power and if process of a
change-over is manual, serious time is not only wasted but it creates
room for human error (in the area of change over connections) which
could result in great economic loss (Ahmed, Mohammed & Augusibo,
2006).
This project is all about the construction of an automatic generator
change-over panel with timer which aids in the switching over to
alternation power supply authority i.e.Power Holding Company of Nigeria
1
(PHCN) popularly known as NEPA which is the main power regulating
body in Nigeria. This project consist of circuit breakers, electromagnetic
contactor which carry heavy load current relay which work with the
principle of electromagnetic induction because it will receive electrical
signal to trigger and neumatic timer all incorporated and interconnected
to achieve the desire goal (Jenyo, 2007).
Also this project is constructed in such a way that provision is
made for manually operation (it can be operated manually) when
necessary for required for example, in the situation whereby voltage
supplied by the authority (PHCN) is fluctuating and one may decided not
to use it, so the constructed automatic change-over panel can be
permanently switch to generator set temporarily pending the time that
utility supply is stable moreover in the hospital where where surgery
operations is needed to be carry out and power outage for even five
second cause damages, one may decide to neglect the supply from
authority (PHCN) and permanently switch the panel to manual operation
pending the time or period by which surgery operation is completed.
During the pending period this change-over will be working continuously
in manual operation. Fill someone or the operation has to switch over to
automatic operation. As said earlier, provision is made for these types of
2
generation in this project and there is separate switch that performed
the function.
1.2 AIM AND OBJECTIVE OF THE PROJECT
The aim of the project is to design and construction automatic
change-over switch load from the mains power supply (PHCN) to a
backup power supply (Generator) with simplicity.
The advantages of this project cannot be over emphasized, since
outage is a major problem is the advent developing nations like Nigeria,
for example, power failure of minute in an airport terminal can create
losses that could run into millions of dollars due to loss in air traffic
system control the ability for back-up to start and change-over
automatically becomes imperative under such circumstances.
Also, this project could play a large role in the security in banks
and companies i.e. an outage of up to ten minute in an organized setup
is enough to do all the damage required with such an automatic changeover device in place the generator backup would no longer have to
depend on security men and of course reduced fear of system
breakdown in the companies there by ensuring smooth running of
economics activities.
1.3
SCOPE OF THE PROJECT
3
Basically, this project is a three phase automatic change-over
device with the power capacity of 50KVA. Generator as deducted from
my calculations it shows that generator of power rating ranging from
0.5KVA to 50KVA is required to be use for this project though the
contacts of electromagnetic contactor relays and circuit breakers. Also
the maximum load current should be between the ratings of 10A to 90A
load current. Therefore the use of 10Amperes in this project is because
of future extension.
4
CHAPTER TWO
2.1 LITERATURE REVIEW
The purpose of this project is to design and construct this unique
equipment that provider a solution to the power supply problem we are
facing in Nigeria today. The automatic change-over switch can be
describe as a unique power supply to another as well maintaining
constancy in the supply to a particular network load this equipment to
be designed and constructed in this project will interface between two
different electrical power source (e.g. the main supply and the
generator).
The main source of supply to the unit is obtained directly from the
public supply (PHCN) the relaying and triggering system serve as an
interface between the supply and the load hence the load is not directly
couple to the public supply. The triggering units sense the failure in
supply and immediately the ignition switch of the generator.
Power change-over switch are two different mode of operation
namely.
2.2 MANUAL CHANGE-OVER SWITCH
In this mode of operation when there is any mains failure i.e.
(PHCN) outage there is need for personnel to start the generator
manually and wait till the generator attains synchronous speed. Only
5
after the generator attains synchronous speed can the operators
transfer the load to the generator.
In the event that mains supply is restored the operation has to the
operation has to transfer the load back to the mains supply and turn
OFF the generator this is done by manually relapsing the change-over
breaker. To ensure safety of this operation the two breaker of the
change-over switch must be operation are quit cumbersome. Restoration
of power is usually a prolonged process which cause delay. The process
may also result in heavy losses and damage could be done to sensitive
loads during this manual process.
2.3 AUTOMATIC CHANGE-OVER SWITCH
In this mode of operation when there is any mains failure there is
no need of the employment of the personnel as the change-over switch
will start automatically it sensing power from the mains supply and there
after switch the loads to the generator supply upon it attaining
synchronous speed. Upon restoration of the mains supply the switch
again sense it and transfer the load back to the mains supply.
The type of automatic change-over switch used which differs from
the other (semi-conductor controlled switch type) in terms of the type of
load transfer or switching panel is the contractors, this design of load
transfer panel makes use of mainly relay and contactor combination, its
6
operation is based on the hierarchical rank of contactor relays. It
consists of some relays which serves several purpose these are :1.
Mains Contactor
It carries the bulk of the load its auxiliary when the mains supply
(PHCN) in ON, the mains contactor responds to the input by
closing its contacts which enable it to get energized causing
indicator lamps on the panel to illuminate of these lamps indicate
that the mains supply is ON.
2.
Mains Auxiliary Contactor
It is usually present in the generator circuit when there is power
outage in the mains supply the contact of the mains auxiliary
contactor which is in the generator circuit close thereby sending a
signal to start the generator
3.
Generator Contactor
After starting the generator automatically, the load is then
transferred to the generator contactor
4.
Generator Auxiliary Contactor
It is the generator auxiliary contactor that is responsible for
ensuring that only a power sources gets to the load at point in
time. When there is mains supply failure, it break the mains supply
line to the load before the generator line is activated. Upon
7
restoration of the mains power supply the generator auxiliary
again break the generator line before the load is transferred to the
mains supply.
Because this design makes use of relay and contactor combination
it is said to have the following advantages
 It can switch alternating current
 It can switch high voltage
 It is useful when high current are to be used
 It is switch many contacts at once. This quality make them
flexible
It has the following draw back

Poor sensing ability to fluctuation due the fact that relays do
not function optimally at low voltages.

Switching time in the event of mains power supply outage is
low because switching is done in the basis of energizing and
de-energizing of the relay coil

Relays generate a lot of heat during switching action which
could caused short circuits which are very hazardous

Relays draw a lot of power from the power supply thereby
increasing the overall power consumed by the load
8
It time like this, there is really no new invention rather what we
have now are just improvement and innovation on fundamental principle
of obtaining the desired result. Hence, the automatic change-over switch
that is designed and constructed is an improvement on what other have
done over the years.
A past project was designed such that is being supplied from just
three power sources. The present design is such that it would take two
different sources to simultaneously and also give preference to this
power sources with the unique ability to ensure that there is always
power supply to the load at all times.
9
2.4 RELATED WORK
The present invention that related to an automatic change over
device has been designed for a power sources to automatically switch
over system for supplying electric power to an electric load in such a
manner that electric power output from an engine generator in supplied
to the electric load upon occurrence of the power failure of a regular
power sources system as it is been used by used patent on 21st may,
2002.
There is an automatic switch-over known, for example from
Japanese patent application laid-open No 5-64382 and the likes which is
designed so that a switch in
change-over to supply electric power
output from an engine generator to an electric load upon occurrence of
power failure of a regular power source system.
In such an automatic switch over device for the power source it is
necessary not only to provide an emergency automatic switch-over
mechanism, but also to provide a measure for enabling switch by an
operator’s manualsoperation in case of failure or the like of a control
unit.
This automatic switch-over devices for a power source comprise
switching unit which has first and second individual contacts which is
individually leading to a regular power source system and an engine
10
generator and common contact leading to an electric load where the
common contact can be alternatively electrically controlled unit for
controlling the switching unit in such a manner that the common contact
is electrically connected to the second individual contact in response to
the regular power source system being electrically failed and the
common contact is electrically connected to the first individual contact in
response to the restoration of said regular power source system, where
in the switching unit is made of a relay which consist of : A see-sew-type turn member carried on a support frame for
turning movement between first turned positions in which the
turn member permits the common contact to be electrically
connected to the first individual contest and a second turned
position in which the turn member permit the common contact to
be electrically connected to the second individual contact.
 A spring member for exiting a spring force for retaining the turn
member in one of the first and second turned position in
response to the turning movement of the turn member passing
through a central point between first and second turned position.
 A first solenoid capable of exerting an electromagnetic force for
driving the turn member toward the turned position against the
spring force of the spring member.
11
 A second solenoid capable of exerting an electromagnetic for
driving the turn member toward the second turned position
against the spring force of the spring member.
With such arrangement of the feature the supplying of electric
power from the engine generator to the regular power source system
and the supplying of the electric power from the regular power source
system can be automatically switching manner by the control unit.
According to a second aspect and feature of the present design in
addition to the arrangement of the first feature a neumatic timer is
incorporate to achieve the aim of letting the switching system switch
OFF the generator set when not required for use in a case where power
is not restored by the PHCN (supply).
The
present
design
has
been
achieve
with
the
above
circumstances in view and it is an object of the present invention to
provide and automatic change-over for a power source where in the
switching can be achieved by the operator’s manual operation without
provision of a special mechanism.
The above and other objectives features and advantages of the
design will become appeared from the following description of the
preferred embodiment taken in conjunction with the accompanying
diagram (us patents issued 21st May, 2002
12
Fig. 2.1 Switching Transistor
13
Fig 2.2 Flip Flop
14
The circuit diagram of the flip flop and switching transistor stage
of the related art.
Another related art was the development of a single phase
automatic change-over switch. This also related to the present invention
i.e. it switches electrical power supply from public supply to generator in
the event of a power outage or insufficient voltage but it is apply to
single phase system while the present invention is apply to three (3)
phase system, moreover, the system uses an electronic control circuit
involving integrated circuit invention uses electromagnetic contactor and
circuitbreaker for its operation.
In this related art, the electronic control monitors the incoming
public supply voltage and detects when the voltage drops below a level
that electrical or electronic gadgets can function depending on the utility
supply. In these cases, 160V is the limit in which the system changeover the public supply or generator.
The sensor stage monitors the unregulated voltage dropped across
R1and R2 as show in the above diagram in Fig.1.1
The voltage feeds an input on ICI which compare this input with a
fixed reference across VR1. The drop across at 160V A.C is set as the
reference. Any voltage drop below this, send a low to the input of the D15
flip flop to switch the transistor OOF is set mode. Once the transistor 1
switch OFF, the relay in de-energized and the contacts change-over.
Two relays are connected in parallel RLA1 is 10A relays which switch the
battery 12V to the ignition coil of the generator (starter coil) and switch
it OFF once public supply is back.
The second relay RLA2 is 30A relay that selects generator or public
supply output to load as show in Fig. 1.1
The generator output is normally closed. Hence, once deenergized the generator output is fed to load and one energized (by the
presence of public supply) the relay (normally open contacts connects
public supply output to load).
2.5 REASONS FOR AUTOMATIC CHANGE-OVER SWITCH
The purpose of this project is to design and construct a unique
equipment that provide a solution to the erantic power supply problem
we are facing in Nigeria today. The automatic change-over switch can
be describe as a unique switching system which can be used to change
from one power supply to another as well as maintaining constancy in
the supply to a particular network or load. This equipment to be
designed and constructed in this project will interface between two
different electrical power sources. (e.g the main supply (PHCN) and the
generator).
16
The mains source of supply to the unit is obtained directly from
the public supply (PHCN), the relaying and trigging system serves as an
interface between the public supply and the load, hence the loads is not
directly coupled to the public supply the trigging unit is also coupled with
the generator output to provide a connection between the generator
and the load. When there is power outage form the public supply the
relay and triggering unit sense the failure in supply and immediately
trigger the ignitron switch of the generator
2.6 PROBLEMS OF AUTOMATIC CHANGE-OVER SWITCH
Problem that can occur on the automatic change-over switch is
when the relay is damaged the changeover switch will not be able to
perform automatically.
17
CHAPTER THREE
3.1 METHODOLOGY (MATERIAL AND METHODS)
This project is constructed using locally made materials with
special consideration on economical, mechanical, electrical and other
physical properties of materials.
Since, the materials have those properties which are closely to one
another; I found it very difficult to discard one from other, but with the
advice of my project supervisor and some technician, I am able to
choose those one that are that are more appropriate for this project,
3.2 CIRCUIT CONDUCTOR
Conductor: is a material which offers a low resistance to the flow
of current. And such a conductor for everyday use must be of low
electrical resistance.
(i)
Of low electrical resistance
(ii)
Mechanical strong and flexible
(iii)
Relatively cheap for practical purpose
Cable is the length of single insulated conductor (solid or
stranded). A current carrying conductor form part of a circuit or final
sub-circuit, but excluding the earth continually conductor.
Note:- for frequency stop-starting, the cable may have to be heavier
because starting current
18
Fig 3.1 Circuit Conductors
3.3 CIRCUIT BREAKER
This is defined as electro-mechanical device design to make and
break the electric circuit under normal and abnormal conductor such as
those of short circuit, the circuit being broken automatically. The
majority of circuit breaker is either oil or air blast types.
Regulation 433-2 require the characteristic of the device (fuse or
circuit breaker) protecting the circuit to be coordinated with the
conductor forming the circuit such that.
(i)
Its normal current (fuse rating) or current setting for circuit
breaker (IN) is not less than this design current which is the
minimum or normal circuit current (IB).
19
(ii)
The current which operate the fuse or circuit breaker, causing it
to disconnect the circuit (RZ). does next exceed 1.45times the
lowest of any current carrying capacities (IZ) for the circuit
conductor, using formula: IB<IN<IZ and IZ<1.45IZ.
(iii)
It is not greater than the current-carrying (IZ)of the circuit
conductor.
Fig 3.2 Circuit Breaker
3.4 RESET TIMER
A relay designed to operate after a calculated time delay is called a
“timer relay” or timer. If the timer delay is fixed regardless of the input
of the relay (in excess of pick-up value) the relay is termed “definite
timer”. The amount of time delay may less for greater input to the relay,
such relay are called “inverse” very inverse or “extremely inverse”
20
depending on the extent which relay is reduced for an increase in the
input to the relay.
A relay designed to have no intentional time is said to be
instantaneous.
START AND STOP BUTTONS
These two push buttons are used to close and open the circuit
respectively. The start push button is a normally open type (NO) while
the stop push button is a normally close (NO) type to breaker the circuit
when need arise
3.5 CONTACTOR
Is a device designed for repeatedly making and breaking an
electronic power circuit. It is usually operated magnetically. It can be
operated in line or be remotely governed by pilot devices or relay. And
when there is a supply to contactor coil it becomes energized for
movements while if there is no supply it will breaker the contact.
21
Fig 3.3 Contactor
PROCEDURE
(i)
A plate of copper metal not thicker than 2mm is taken to the
workshop
(ii)
This is then cut into required dimension by the use of chisel and
hammer
(iii)
After cutting into pieces is then drilled at the required place
(iv)
A file is used to smooth the shape in none accurate dimension
22
PRECAUTION
(i)
Tolerance should be given to each dimension of the hole to
avoid unnecessary large hole
(ii)
The contactor must be of the same with the provided for it
(iii)
The hole for the contactor case should be wide enough to
prevent friction during attraction and releasing of contactor
(iv)
Care should be taken not to use unnecessary high pressure
during chiseling, this may damage metal sheet
(v)
A very sharp chisel should be used to accurate dimension
otherwise the gap between the groove maybe chipped up and
rendered the useless.
ASSEMBLING OF THE AUTOMATIC CHANGE-OVER COMPONENT
INTO THE CASING
(I)
The process of assembling the change-over panel was carried
out based the terminal were set into the terminal rail and boded
rigidly to prevent vibration
(II)
The return spring was then fixed to the right place in the
contactor case
(III) The reset time is then attached to the base of the case together
with the rail stand
23
(IV) The contactor and circuit breaker attached to the rail stand and
the contactor case is fixed in the right position in the terminal
house
(V)
Pressing the contactor case against the force of the retaining
spring and role whether the contactor is or not
Fig. 3.4 front view of the
3.6 OPERATION OF TNMER RELAY
Timer relay are based on the electromagnetic induction principle
which can only be applied where the actuating quantity or quantities
A.C, they cannot be operated by D.C, since we are primarily concerned
with an A.C system. This may be good place to restate a basic principle
which should be kept in the back every operations mind.
24
Relay operate for the reason only
(i)
The AC quantity to which the relay respond has reached the
setting for which the relay is calibrated
(ii)
The timer relay contactor are closed some mechanism mean.
This could be when time of change from utility supply to
generator is reach in the panel or by someone poking the
contactor either accidentally of intentionally and sometimes
removing or replacing a timer relay cover will cause a relay to
operate.
3.7 PRINCIPLE OF OPERATION
The change-over panel consists of two (2) 100A circuit breaker
which serves as a means of isolation and at the same time a protective
device. The circuit breaker A is used to feed in the utility supply to the
system while circuit breaker B is used to feed in the generator set supply
to the system. Also in the panel, there are six (6) contactors, which are
electromagnetic device that are design to carry current of difference
capacities. Contactor A is load contactor that carries the utility supply to
the load while B is equally a load contactor that carries the generator set
supply to load. Contactor C is a control contractor which equally serve as
relay the contractor is also been in operated with a relay timers monitor
the function of the utility power contractor or load contractor. The stop
25
button is connected to supply from the red ohase through the normally
close (NC) of the stop button to the contractor. Contractor C is equally
meant to carry DC supply through the contractor for the purpose of
supplying the contractor F.
Contractor D serves the same function as that of C but is only
monitor the generator set load contractor with the help of the timer on
it. The relay timer on contractor D helps in relaying the operation of
contractor D helps in relaying the operation of contractor B so that the
generator set will not be loaded before it maintain stability.
Contractor E is mean to discharge the work of the kick starter on
the generator set and to equally control work of operator D when the
generator must have given out an output.
Contractor F is a DC contractor of the 12v. it is used to start the
kick starter of the generator set. It is connected through the
P= IL VcosѲ
But it is 3 Phase
...P=3L Vcosϴ
P= power supply in watts
Where
IL= load current in Ampere
V= supply voltage in volts
26
Cos = power factor (p.f) but p.f ... cosec 0.8
P = 50KVA
IL=?
V = 415V (3phase)
... IL =
Since we cannot set material for exactly 86.9A, therefore we
decide to choose for 100A and also for future extension.
27
Automatic Change-Over Panel
28
CHAPTER FOUR
CONSTRUCTION
4.1 LIST OF COMPONENT USED
The following electronic components used in the project are list
below
(1)
Voltmeter
(2)
Casing
(3)
Vero-Board
(4)
Transformers DC 12V
(5)
Diodes
(6)
Capacitors 100
(7)
Resistors 4k
(8)
Contactors
(9)
16mm2 Cables
(10) 1ooAmp connector
(11) Bolt and Nuts
(12) Indictor light
(13) Relay three phase
(14) 555IC timer
4.2 VERO BOARD: is a brand of strip-board, a per-formed circuit
board material of cooper strip on an insulating board which
29
originated and developed in the early 19960s by the Electronics
introduced as a general purpose material for use in constructing
electronic circuit differing from purpose-designed printed circuit
board (PCBs)in that a variety of electronic circuits may be
constructed using a standard wiring board. The first single-size
Vero-board which, with world-wind use over five decades, have
become knownas strip-board are own taken to be synonymous.
The VPE Electronics department was formed early in 1959
when managing director Geoffrey Virden-Roe hired two former
Saunders-Reo Ltd employees, peter H Winter (aircraft design
department) and Tony Fitz Patrick (Electronics division). After the
failure of a project to develop machine tool control equipment the
department remained remain operative as a result of electronics
material Vero-board. The printed circuit board (PCB) had become
commonplace in electronics production by the mid 1905s and new
equipment utilizing PCBs was displayed at the 1959 Radio and
Electronics
components
manufactures
federation
(RECMF)
exhibition held in Dorchester hotel. Production of the proposed
new product, Vero-board, was undertaken by the machine tool
department.
30
Bought in sheet of 1.6mm (0.2in) copper-clad SRBP printed
circuit material were out to give 122mm x 456mm (48in x 18in)
size boards with the individual boards then being machined to
form the final product according to the original Vero-board
specification. A multiple milling cutter with suitably shaped cutting
teeth, was fabricated to be used in removing part of the bonded
copper on each board leaving twenty one (21) conductive strip.
The machining problems were encountered due to the nonavailability in 1960, of advanced printed circuit board milling and
drilling techniques production rates improved and on 1961 Vero
electronics Ltd was formed as a separate company to market the
increasing sales of Vero-board
Fig 4.1 Vero Board
4.3 BREAD BOARD (or proto-board): - is usually a construction base
for prototyping of electronics the term “Breadboard” is commonly
31
used to refer to a solder less breadboard (plug board). A
breadboard was originally was a flat wooding cutting board use to
support to a loaf of bread (or other foods) while it was been shed;
this original meaning is still in use but has a new additional
meaning as “ a base for prototyping” the concept of “breadboarding” as prototyping is not confined to be use by mechanical
engineers. Because the solderless breadboard for electronics does
not require soldering, it is reusable this makes it easy to use for
creating temporary prototypes and experimenting with circuit
design.Older breadboard types did not have this property.A stripboard (Vero-board) and similar prototyping printed circuit board,
which are used to build semi-permanent soldered prototypes or
one-offs, cannot easily be reused. A variety of electronic systems
may be prototyped by using breadboard for small analog and
digital circuit to complete central processing unit (CPUs)
In early days of radio, amateurs nailed bare copper wire or
terminal strips to a wooden board (often literally a cutting board
for bread) and soldered electronic component to them. Sometimes
paper schematic diagram was first glued to the board as a guide to
placing terminal then components and wires installed over their
32
symbol on the bread board schematic. Using thumbtacks or small
nails as mounting post was also common.
Breadboards have overtime, with the term now being used
for all kind of prototype electronic devices for example.
Us patent 3,145,483, field in 1961 and granted in 1964;
describe a wooden plate breadboard with mounted springs and
other facilities. Us patent 3,496,419. The breadboard most
pluggable (solderless) breadboard it was designed by Ronald
Portugal of El. Instrument inc. in 1871.
Fig 4.2 Breadboard
4.4 SOLDERING IRON:-is a hand tools use in soldering it supplies
heat to melt the solder so that it can flow into the joint between two
work pieces. A soldering iron is composed of heated metal tip and an
33
insulated handle. Heating is often achieved electrically by passing an
electric current (supplied through an electrical cord or battery cables)
through a resistive heating element. Cordless iron can be heated by
combustion of gas stored in a small tank. Often using a catalytic heater
rather than flames simple irons loss commonly use than in the past
where simply a large copper bit in a handle, heated in a flame.
Soldering irons are most often used for installation, repairs and
limited production work in electronics assembly. High volume production
lines use other soldering methods. Lines irons may be used for soldering
joint in sheet metal object less common uses include pyrography
(burning designs into wood) and plastic welding.
Fig 4.4 Soldering Iron
34
Voltmeter
Voltmeter is used to indicate the voltage of the generator and that
of the utility supply
Casing
This is the structure which enclose the main construction of the
automatic change-over panel. It is constructed using metal sheet of
thickness 2mm. the shape of the change-over panel is first drawn on a
plane paper with dimension that will adequately accommodate the
change-over panel.
The required dimension is then traced out on the iron sheet chisel
and hammers where used to cut the traced end.
After this, each part are joined together by the use of welding
machine and the necessary holes for both and screw where drilled on
the change-over house required.
After the construction, this change-over panel is then painted. The
tools used for the construction are: Chisel
 Hammer
 File
 Welding machine
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4.5.1
Testing, maintenance and discussion
Testing is an important process in the engineering field especially
in both electrical and electronics engineering.
Therefore, testing can be define as the process by which any
faulty condition is detected before a dangerous situation arose.
Having designed and construction or installed s system with an
appropriate selected materials component and equipment what now
remain is to put the system into use.
However, before the system is put use, it must be tasted and
inspected to ensure that is complies with regulation of installation.
Below is the test carried out.
 Polarity test
 Insulation resistance test between the alive and neutral conductors
 Insulation resistance test between earth and non-earthling
conductors
 Earthling test
4.5.2
POLARITY TEST
This test is carried out on the construction of automatic change-
over panel to ensure that only live conductor is taken through the
beaker on the load contactor.
36
4.5.3
INSULATION RESISTANCE TEST BETWEEN THE LIVE
AND NEUTRAL CONDUCTORS
An insulation resistance test was made between live and neutral
conductor to ensure that there are no short-circuit in the wiring
One lead from the insulation tester was connected to the outgoing
live terminal and the other to the neutral of the main switch. The
instrument is operated and accurate reading was reading out.
4.5.4
EARTLING TEST
This test carried out to ensure that there is no leakage to the body
of appliance.
On led of ohm meter is placed on conductor and the other lead to
the body of appliance. Zero resistance indicates that there is no leakage
to the body.
4.6 MAINTENANCE OF CONTACTOR AND IINSTALLATION
Generally the contact and wiring of the contactor should be
properly maintained for adequate functioning of the contactors. In
addition, the following should be a also be put into consideration. To
replace an operating coil, the contactor must be removed from enclosure
and the following procedure must be under taken.
37
(i)
Remove the spring-clip on either side of the contactor, carefully
live the auxiliary contact compress coil magnet slight and take
whole magnet system and moving contact carries from auxiliary
contact button
(ii)
Invert the assembly and lift out the lift magnet and coil
vertically, taken care that the magnet spring remain in place.
Note the position of the coil terminations.
(iii)
Change the coil and re-assemble the unity by reversing the
above procedure, remembering to compress slightly the magnet
when replacing the auxiliary contact.
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CHAPTER FIVE
5.1 CONCLUSION
The automatic change-over switch has immense advantage in
every area where power is required it is a fact that there is hardly any
aspect of human life were electrical power is not required, at home,
offices, hospital, etc.
It find a wide application scope, wherever the re-ability of
electrical supply is necessary, for switching to an alternative
source from main.
5.2 RECOMMENDATION
The automatic change-over switch is needed in every home and
offices because of the fact that it’s reliable, it’s durable, and it’s
affordable and is ability to provide immediate automatic switching from
the public power source to other sources.
It is recommended that further work be done on this change-over
switch on large scale, for instant an automatic change-over switch that
can be use in an industry.
39
REFERENCE
B.L. and A.K. Theraja (1997): Electrical Technology, S. chand company
LTD
Engr. A.O Aduloju (2003): Electrical Power System, Evidence Nigeria
Venture
Engr. M.B Jenyo (2007): Electrical Power System III & IV lecture Notes,
Unpublished
Engr. T.A. Mustapha (2006): Electrical Power System I & II inn lecture
Notes, unpublished
Internet Research: http://www.electricalsolution.com
M.S. Ahmed, A.S. Mohammed & C.B. Augusibo (2006): Development of
a single Automatic change-over switch Federal University of
Technology Minna.
US patent issued (2002):Automatic Generator switch-over Device for
power source, http://www.patentstorm.us
40
BILL OF ENGENEERING MEARSUREMENT AND EVALUTION (BEME)
The table below shows the cost estimate in naira and kobo of
constructed automatic change-over panel.
Bill of Engineering Measurement and Evaluation
S/No
Description of
Quantity
Rate
Amount
materials with
Required
N:k
N:k
complete specification
1.
Transformers
2
500
1,000:00
2.
Diodes
8
50
400:00
3.
Capacitor
4
50
200:00
4.
Resistors
6
10
60:00
5.
555lc
2
150
300:00
6.
Relays
4
150
600:00
7.
Contactors
2
1500
3,000:00
8.
Vero-board
1
150
150:00
9.
16mm2
5yard
200
1,000:00
10.
100Amp connector
5 piece
200
1,000:00
11.
Casing
1
8000
8,000:00
12.
Timer (neumatic)
1
250
250:00
13.
Bolt and nuts
100
100:00
14.
Indicator light
50
150:00
15.
Labour cost
3
7,790:00
Total
Cost
24,000:00
41