PROJECT ON AUTOMATIC TRANSFER SWITCH (ELECTRICAL).pdf

BENG EEE PROJECT WORK-AIT copyright reserved 2015
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DECLARATION PAGE
SIGNED COPYRIGHT/DECLARATION OF AUTHORSHIP
This is to declare that, the research work underlying this Thesis has been carried out by the
under mentioned students under the supervision of the under-mentioned supervisor. Both the
students and the supervisor certify that the work documented in this Thesis is the output of
the research conducted by the students as part of their final year project work in partial
fulfillment of the requirements of the Bachelor of Engineering in Electrical and Electronic
Engineering Degree.
Students
Ephraim Komla Darkeh
Signature ……………………... Date…………………........
Ebenezer Ofori Mintah
Signature …………………….. Date ……………………
Inkoom Romeo
Signature …………………….. Date ……………………
Supervisor
CK Tsagli
Signature …………………….. Date ……………………

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ACKNOWLEDGEMENT
Thanks, praise and adoration to God almighty for his peace, kindness and merciful thoughts
that we still live to fulfill his promise.
Much blessing to our supervisor Mr. CK Tsagli for his fatherly guidance to make this studies
a reality. We say thanks and God richly bless him for his motivation and support to make this
studies a success.
Lots of thanks also go to all our course mates for their assistance throughtout the studies and
also to the entire lecturers at the Electrical/Electronics Engineering department.
Finally, to everyone who through one way or the other made this study successful, we say
thank you and God richly bless you.

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ABSTRACT
Power failure or outage in general does not promote development to public and private
sector. The investors 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 banks and lots more.
This project presents the design and construction of an automatic transfer switch (ATS) that
switces power supply from public supply to generator once there is a public power supply
outage and it does this automatically. This is achieved by the use of integrated circuits that
have timing abilities and relays to effect switching.
With automatic transfer switch (ATS), electrical power supply is switched from public supply
to a stand-by plant without or with little human intervention in the event of power outage or
insufficient voltage.

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LIST OF ACRONYMS
ATS – Automatic Transfer Switch
MCS – Mains Control Switch
AUTO – Automatic
MAN – Manual
CB – Circuit Breaker
MK – Main Contactor
GK – Generator Contactor
NO – Normally Open
NC – Normally Close
T - Delay Timer
R - Relay
G - Green lamp
RL - Red lamp
S – Signal
L – Live line
N – Neutral line

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TABLE OF CONTENT
Declaration ………………………………………………………….......................... i
Acknowledgement …………………………………………………………………...i
Abstract ……………………………………….……………………………………..ii
List of acronyms…………………………………………………………………….iii
List of Tables………………………………………………………………………. iv
List of figures………………………………………………………………..……….v

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CHAPTER ONE INTRODUCTION
1.1 Background Information ............................................................................................10
1.2 Aim/Objective............................................................................................................11
1.3 Scope..........................................................................................................................11
1.4 Research Questions ....................................................................................................11
1.5 Limitations .................................................................................................................11
1.6 Organization Of The Project Work............................................................................12
CHAPTER TWO LITERATURE REVIEW..............................................................13
2.1 General Operation Of Automatic Transfer Switch (ATS) .........................................13
2.2 Specification Of Automatic Transfer Switch (ATS)..................................................13
2.3 Types Of Automatic Transfer Switch (ATS) .............................................................14
2.4 Materials For Automatic Transfer Switch (ATS) ......................................................15
2.4.1 Relay .....................................................................................................................15
2.4.2 Contactor...............................................................................................................18
2.4.3 Timer (On Delay Relay) .......................................................................................19
2.4.4 Circuit Breaker......................................................................................................20
CHAPTER THREE RESEARCH METHODOLOGY AND MATERIAL...............24
3.1 Materials for the Design of ATS................................................................................24
3.2 Components Specifications........................................................................................25
3.2.1 Circuit Breaker – Dz47-63(C45n) Miniature Circuit Breaker..............................25
3.2.2 Contactor- 4 Pole 10amp, Telemecanique Lc1 D1810m7....................................26
3.2.3 Switch ...................................................................................................................26
3.2.4 Relay - 60.12 220vac Relay Switch......................................................................26
3.2.5 Relay – 12VDC Omron (Vde 0435) .....................................................................28
3.2.6 Time Relay – 12VDC (Ah3-1/2/3) .......................................................................28
3.2.7 Time Relay (Ah3-3(St2p Ah3-2)) – 220VAC ......................................................29
3.2.8 Plastic Panel Box ..................................................................................................30
3.3 Tools Used For The Construction Of The ATS .........................................................30
3.4 The Wiring (Power) Diagram Of ATS.......................................................................31
3.4.1 Description And Explanation Of Power Diagram ................................................31
3.5 The Control Diagram Of ATS....................................................................................32
3.6 The Basic Operation Of ATS.....................................................................................32

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CHAPTER FOUR RESULTS, ANALYSIS AND DISCUSSIONS ………………….....22
4.1 Installation of The Constructed ATS ………… …………………………………….22
4.2 Installation Precaution ……………….................................................................……22
4.3 Connecting Power Source And Load Lines………………………………………….23
4.4 Applications Of ATS ………………………………………………………………..24
4.5 Market Analysis ……………………………………………………………………..25
4.6 Market Trends ………………………………………………………………………26
CHAPTER FIVE CONCLUSIONS AND RECOMMENDATIONS ………………...28
5.1 Conclusion …………………………………………………………………………..28
5.2 Recommendation ……………………………………………………………………28
REFERENCES …………………………………………………………………………….29
Books: ……………………………………………………………………………………...29
Web Pages: ………………………………………………………………………………...29

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LIST OF FIGURES
Figure 2-1 A relay.....................................................................................................................15
Figure 2-2 A contactor..............................................................................................................18
Figure 2-3 A Timer ...................................................................................................................20
Figure 2-4 A Miniature Circuit Breaker...................................................................................21
Figure 2-5 Parts of a circuit breaker........................................................................................22
Figure 2-6 A 3 – pole vacuum circuit breaker..........................................................................22
Figure 2-7 An air breaker.........................................................................................................23
Figure 2-8 An oil circuit breaker..............................................................................................23
Figure 3-1 Actual designed ATS...............................................................................................24
Figure 3-2 Power diagram of constructed ATS........................................................................31
Figure 3-3 Control diagram of constructed ATS......................................................................32
Figure 3-4 : A picture showing the final constructed ATS .........Error! Bookmark not defined.

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LIST OF TABLES
Table 3-1 Specifications of circuit breaker..................................................................25
Table 3-2 Specifications of contactor ..........................................................................26
Table 3-3 Coil Versions................................................................................................14
Table 3-4 Timing Range.............................................................................................. 16
Table 4-1 Cost Analysis of Materials used..................................................................44

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CHAPTER ONE
1.0 INTRODUCTION
Power instability in most developing countries has created the need for automation of
electrical power generation or alternative source of power to back up the utility supply. This
automation is required as the rate of power outage becomes predominantly high. Most
industries and commercial processes depend on constant power supply and if the process of
change-over is manual, time is not only wasted but also cause device or machine damage due
to human error, which can bring about massive losses. With automation, starting of the
generator is done by a relay which switches the battery voltage to ignition coil of the
generator while the main power relay switches the load to either public supply or the
generator depending on prevailing conditions.
1.1 BACKGROUND INFORMATION
This project is considered due to the energy crisis facing Ghana these days. Because some
industries and companies activities need constant power supply, they acquire stand-by plant
so that in case of power outage they can still stay in business and also prevent damage to
critical equipment and machinery and even to save life.

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1.2 AIMS/OBJECTIVES
The objective of this project is to design and construct an automatic transfer switch (ATS)
that switches electrical power supply from public supply to stand-by plant in the event of
power outage or insufficient voltage.
1.3 SCOPE
The scope of this project work is to design and construct only automatic transfer switch
(ATS) and provide its installation and maintenance procedure.
1.4 RESEARCH QUESTIONS
 What is a Transfer switch?
 What is the difference between a manual and an automatic unit?
 Why should someone go for an Automatic Transfer Switch?
 What size of transfer switch do I need?
 Who should install my transfer switch?
1.5 LIMITATIONS
 Lack of text book in the library to assist the project work.
 Responsiveness to customer need.

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1.6 ORGANIZATION OF THE PROJECT WORK
The chapter organization of this project is as follows:
 While chapter one introduces the whole project.
 Chapter two is about the general over view of the project.
 Chapter three describes the design and construction of ATS, which involves circuit and
control diagram of the system and component specifications.
 Chapter four describes application, results and analysis of the ATS.
 The last chapter talks about conclusion and recommendation, reference and appendix.

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CHAPTER TWO
LITERATURE REVIEW
2.1GENERAL OPERATION OF AUTOMATIC TRANSFER SWITCH (ATS)
Automatic Transfer Switches form integral part of power generation process. They allow
smooth and immediate transfer of electric power between multiple sources and the load.
When the stand-by power plant is operating, the transfer switch prevents dangerous feedback
of current to the utility´s supply system. ATS also ensures that the stand-by plant attains the
right speed before the power is transferred, which is very important and urgent for safe
operation.
The transfer switch monitors utility power supply and when it is interrupt for a certain time
span, starts up the stand-by plant. When the stand-by plant attains its synchronous speed, the
transfer switch disconnects the load from the utility supply and connects it to the stand-by
plant thus restoring electricity to the load. The ATS continues to monitor utility power and
when it is restored, switches the load from stand-by plant to utility. Once the stand-by power
plant is disconnected, it goes through a cool-down routine and it is automatically shut down.
2.2 SPECIFICATION OF AUTOMATIC TRANSFER SWITCH (ATS)
The commonly used specifications to distinguish between various models of ATS are:
 Rated current: 10 amperes to 4000 amperes
 Poles: two, three or four-pole configurations
 Number of phases: single or three phase

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 Frequency: 50Hz or 60Hz
 Voltage: 220volts to 415volts
 Mounting: rack mounted, pad mounted or pole mounted.
There are various types of ATS, the use of which depends upon the requirement of the overall
system and how the load is transferred among the various power sources.
2.3 TYPES OF AUTOMATIC TRANSFER SWITCH (ATS)
The types of automatic transfer switches are as follows:
 Open transition: These transfer switches disconnects load from one power
supply before connecting it to the other, described as a „break before make‟
connection.
 Delay transition: these transfer switches offers an adjustable time period
delay during switching from one position to the other.
 Closed transition: these transfer switches transfers the load between the two
power sources while preventing the momentary power interruption that could
occur when both power sources are present, described as a „make before
break‟ connection.
 Soft load closed transition: these transfer switches extends the overlap time
to multiply seconds, for a smoother transition of load to the stand-by power.
 Bypass isolation: these transfer switches offers an adjustable time period
delay during switching from one position to another.

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2.4 MATERIALS FOR AUTOMATIC TRANSFER SWITCH (ATS)
The system uses a control circuit consisting of electromagnetic devices which has
relays, contactors, timer, circuit breaker, phase monitor and manual switch.
2.4.1 Relay
A relay is an electromagnetic switch that opens and closes under the control of another
electrical circuit. It uses the principle of electromagnetism to open or close one or more
sets of contacts. Because a relay is able to control an output circuit of high power than the
input circuit, it can be considered, in a broad sense, to be a form of an electrical amplifier.
Figure 2-1 A relay
When a current flows through the coil, the resulting magnetic field attracts an armature
that is mechanically linked to a moving contact. The movement either makes or breaks a
connection with a fixed contact. When the current to the coil is switched off, the armature
is returned by a force approximately half as strong as the magnetic force to its relaxed
position. If the coil is energized with DC, a diode is frequently installed across the coil to
dissipate the energy from the collapsing magnetic field at deactivation, which would
otherwise generate a spike of voltage and might cause damage to circuit components. If
the coil is designed to be energized with AC, a small copper ring can be crimped to the

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end of the solenoid. This ring creates a small out-of-phase current, which increases the
minimum pull on the armature during the AC cycle.
2.4.1.1 Types of Relay
Latching relay, reed relay, mercury- wetted, polarized relay, machine tool relay and, solid
state contactor, buccholz relay, solid-state relay and contactor relay which is where our
interest are.
2.4.2 Relay
A relay is an electromagnetic switch that opens and closes under the control of another
electrical circuit. It uses the principle of electromagnetism to open or close one or more
sets of contacts. Because a relay is able to control an output circuit of high power than the
input circuit, it can be considered, in a broad sense, to be a form of an electrical amplifier.
Figure 2-2 A relay
When a current flows through the coil, the resulting magnetic field attracts an armature
that is mechanically linked to a moving contact. The movement either makes or breaks a
connection with a fixed contact. When the current to the coil is switched off, the armature
is returned by a force approximately half as strong as the magnetic force to its relaxed

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position. If the coil is energized with DC, a diode is frequently installed across the coil to
dissipate the energy from the collapsing magnetic field at deactivation, which would
otherwise generate a spike of voltage and might cause damage to circuit components. If
the coil is designed to be energized with AC, a small copper ring can be crimped to the
end of the solenoid. This ring creates a small out-of-phase current, which increases the
minimum pull on the armature during the AC cycle.
2.4.2.1 Types of Relay
Latching relay, reed relay, mercury- wetted, polarized relay, machine tool relay and, solid
state contactor, buccholz relay, solid-state relay and contactor relay which is where our
interest are.
2.4.2.2 Uses of relay
Relays are used:
 To control a high- voltage circuit with a low-voltage signal, as in some types of
modems
 To control a high-current circuit with a low-current signal, as in the starter solenoid
of an automobile
 To detect and isolate faults on transmission and distribution lines by opening and
closing circuit breakers (protection relays)
 To isolate the controlling circuit from the controlled circuit when the two are at
different potentials, for example when controlling a mains- power device from a
low-voltage switch. The latter is often applied to control office lighting as the low
voltage wires are easily installed in partitions, which may be often moved as needs
change.

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2.4.3 Contactor
A contactor is an electromagnetic controlled device (relay) used for switching a power
circuit. The contactor is activated by a control input which is of a lower voltage or current
than that which the contactor is switching. Contactors come in many forms with varying
capacities and features.
Figure 2-3 A contactor
Unlike a circuit breaker, a contactor is not intended to interrupt a short circuit current.
Contactors range from having a breaking current of several amps and 220volts to thousands
of kilovolts (KV) as well as amps.
A basic contactor will have a coil input (which may be driven by either an AC or DC supply
depending on the contactor design) and generally a minimum of two poles are controlled.
Contactors are rated by designed load current, maximum fault withstand current, duty cycle,
voltage and coil voltage.
2.4.3.1 Uses of contactors
Generally, contactors are useful in the following ways:
 Contactors are used to control electric motors, lighting, heating and other electrical
loads.

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 They often used to provide central control of large lighting installations, such as
office building or retail building.
 To reduce power consumption in the contactors coils, two coils latching contactors
are used. One coil, momentarily energized and closes the power circuit contacts
and the other open the contacts.
2.4.4 Timer (On Delay Relay)
A timer is a special type of clock which can be used to control the sequence of an event or
process. Timer can be mechanical, electromechanical, digital, or even software, since most
computers include digital, we used an electromagnetic timer.
2.4.4.1 Electromagnetic timer
Electromagnetic timers have two common types, namelly thermal and cam type. A thermal
type has a metal finger made of two metals with different rate of thermal expansion (steel and
bronze are common). An electric current flow through this finger, and hats it. One side
expand less than the other, and an electrical contact on the end of the finger moves away from
an electrical switch contact, or makes a contact ( both types exist ). The most common use of
this type is now in the “Flasher” units that flash turns signals in auto mobiles or sometime in
Christmas light. Other type of electromagnetic timer (a cam timer) uses a small synchronous
AC motor turning a cam against a comb of switch contact. The AC motor is turned at an
accurate rate by the alternating current which power companies carefully regulate. Gears
slow this motor down to the desire rate and turn the cam.

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Figure2-4 A Timer
The most common application of this timer now is in washers, driers, and dishwasher. This
type often has a friction clutch between the gear train and the cam, so that the cam can be
turned to reset the time.
Electromechanical timers survive in these applications because mechanical switch contacts
are still less expensive than the semiconductor devices needed to control powerful lights,
motors and heaters.
2.4.5 Circuit Breaker
A circuit breaker is an automatically operated electrical switch designed to protect an
electrical circuit from damage cause by over load or short circuit. Unlike CB, which operate
one and have to be replace, a circuit can be reset (either manually automatically) to remain
normal operation. Circuit are made in varying sizes, from small devised that protect an
individual household appliance up to a large switchgear designed to protect high voltage
circuit feeding and entire city.

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Figure 2-5 A Miniature Circuit Breaker
2.4.5.1 Operation of circuit breaker
Magnetic circuit breakers are implemented using a solenoid (electromagnetic) that‟s pulling
force increase with the current. The circuit breaker‟s contacts are held closed by a latch and,
as the current in solenoid increase beyond the rating of the circuit breaker, the solenoid‟s pull
release the latch which then allow the contact to open by spring action. Some type of
magnetic breakers incorporate a hydraulic time delay feature, whereas the solenoid core is
located in a tube containing a viscous fluid, the core restrained a spring unstill the current
exceeds the breaker rating. During an overload, the solenoid pull the core through the fluid to
closed the magnetic circuit which then provides sufficient force to release the latch. The
delay permits brief current surges beyond normal running current for motor starting
energizing equipments, etc. Short circuit provide sufficient solenoid force to release latch
regardless of core position thus by pass the delay feature.

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Figure 2-6 Parts of a circuit breaker
2.4.4.2 Types Of Circuit Breakers
2.4.4.2.1 .MCB (miniature circuit breaker) – rated current not more than 100 A. Trip
characteristic normally not adjustable. Thermal or thermal – magnetic operation
Electrical power systems required the breaking of high current at higher voltages.
Example of high – voltage AC circuit breaker are:
Figure 2-7 A 3 – pole vacuum circuit breaker
2.4.4.2.2 Vacuum circuit breaker – with rated current up to 3000A, this breaker interrupts
the current by creating and extinguishing the arc in a vacuum container. These can only be
practically applied for voltage up to about 35,000V, which corresponds roughly to the

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medium – voltage raged of power systems. Vacuum circuit breaker turn to have longer life
expectancies over haul than do air circuit breakers.
Figure 2-8 An air breaker
2.4.4.2.3 Air circuit breaker – rated up to 10000A. Trip characteristics are often fully
adjustable including configurable trip thresholds and delays. Usually electronically
controlled, through some model are micro processor controlled via and integral electronic trip
unit. Often used for main power distribution in large industries plants, where the breakers are
arranged in draw – out enclose for easy of maintainers.
Figure 2-9 An oil circuit breaker
2.4.4.2.4 Oil circuit breaker (OCB) – it has oil as the quenching medium between the
contacts. When an arc is produced as a result of oil decomposition, hydrogen gas is evolved
which cools the arc and at the same time setup turbulence in the oil and force it into the space
between the contact. As a result the arc is extinguished and the circuit is interrupted. It is
rated up to 63A, 400volts and 50Hz frequency.

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CHAPTER THREE
RESEARCH METHODOLOGY AND MATERIAL
3.1.MATERIAL FOR THE DESIGN OF ATS
Figure 3-1 picture showing the various component for the designed ATS
5
6
8
1
3
7

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1. Mains contactor
2. Relay 1(220VAC)
3. Timer 1 (220VAC)
4. Timer 2(12VDC)
5. Relay 3 (12VDC)
6. Circuit Breakers
7. Relay 2 (220VAC)
8. Generator contactor
3.2 COMPONENTS SPECIFICATIONS
3.2.1 Circuit Breaker – DZ47-63(C45N) Miniature Circuit Breaker
Table 3-1 Specifications of circuit breaker
Specifications
Number of poles 2
Rated Current (A) 10A
Breaking Capacity (A) 6000
Rated Voltage (V) 230V
Rated Frequency 50Hz
Endurance ≥4000
Circumstance Temperature -50
C ~ +400
C

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3.2.2 Contactor- 4 Pole 10Amp, TELEMECANIQUE LC1 D1810M7
Table 3-2 Specifications of contactor
Type LC1D1810M7
Pole 4P
Rated current (A) 10
Rated voltage(V) 230
Ambient temperature -5o
C~+40o
C
Type of Instantaneous release B,C,D
Rated short circuit breaking capacity Icn(KA) 10
3.2.3 Switch
Type – single pole double throw (SPDT)
3.2.4 220VAC Relay Switch
Specification
Contact Ratings
Contact Resistance 50m1/2 (1A 6VDC)

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Contact capacity
10A 10A/5A(NO/NC)
28VDC/220VAC 28VDC/220VAC
Insulation Resistance 500M1/2, 500VDC
Dielectric Strength
BCC 1500Vr.m.s 1 minute
BOC 1000Vr.m.s 1 minute
Operate Time 30ms /20ms
Terminal Type Socket
Coil Ratings
Nominal Coil Power 1.5W/2.5VA
Table 3-3 Coil Versions
Nominal Voltage
VDC
Pull-in Voltage
VDC
Release Voltage
VDC
Coil ResistanceΩ:±10%
6 4.8 0.60 4.6
12 9.6 1.20 19
24 19.2 2.40 80
48 38.4 4.80 320
100 80.0 10.0 1700
110 88.0 11.0 75

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3.2.5 Relay - 12VDC OMRON (VDE 0435)
Specification
Rated voltage 12VDC
Rated current 75mA
Coil resistance 160
Coil inductance Arm. On 0.73H
Arm OFF 1.37H
Must operate voltage 80% max
Must release voltage 10% min
Maximum voltage 110%
Power consumption 0.9W
3.2.6 Time Relay - 12VDC (AH3-1/2/3)
Specification:
Voltage DC12V-48V AC12V-380V50HZ
Power expend DC1.0W AC1.0VA
Control output 5A220VAC
Insulation Resistance DC500V 100MΩ
Dielectric Strength BCC1500VAC BOC1000VAC
Operating Temperature -10°C~50°C
Humidity 35%~85%

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Life Mech:107 Elec:103
Weight ≈50g
Table 3-4 Timing range
Switch position 1 2 3 4
A
B
C
D
E
F
G
0.05-0.5s
0.1-1s
0.5-5s
1-10s
5-60s
0.25-2m
0.5-4m
0.05-5s
0.1-10s
5-50s
10-100s
1-10m
2.5-20m
5-40m
2.5-30s
5-60s
0.5-5m
1-10m
5-60m
0.25-2h
0.5-4h
0.25-3m
0.5-6m
2.5-30m
5-60m
0.5-6h
1-12h
2-24h
3.2.7 Time Relay (AH3-3(ST2P AH3-2)) – 220VAC
AH3-3 series electric time relay have small size, light weight, high delay precision, wide
delay range, good reliability, long life characteristics etc. This time relay complies with
international standards and is suitable for kinds of high precision and reliability auto control
situation to delay control.

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Repeat error: <0.5%+20ms
Contact capacity: AC220V, 3A
Delaying range: 0.1seconds-12hours
3.2.8 Plastic Panel Box
The purpose for choosing plastic panel box for the casing of the ATS is as follows:
 Plastics are durable and degrade very slowly; the molecular bonds that make plastic
so durable make it equally resistant to natural processes of degradation.
 For decades one of the great appeals of plastics has been their low price.
 Plastics as insulators thus do not require earthing when used as casing.
 Plastic containers are readily available.
3.3 TOOLS USED FOR THE CONSTRUCTION OF THE ATS
 Drilling Machine
 Hacksaw
 Ray Bit Gun
 File
 Screw Driver
 Pliers

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3.4 THE WIRING (POWER) DIAGRAM OF ATS
Figure 3-2 Power diagram of constructed ATS
3.4.1 Description And Explanation Of Power Diagram
When the three phase supply from the utility source is taken, it is made to pass through the
contactor, C1 and the load is supplied with electrical power after being controlled. Thus
energizing its coils to make circuit before the load is connected since contactors are designed
to make and break an electrical power circuit without causing damage to the equipment.
Therefore, the three-phase supply been supplied by the stand-by power plant is also passed
through the contactor, C2, after energizing closes its contactors to make electrical circuit to

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the load. C1 and C2, however, provide a mechanism called Mechanical Interlock. This is a
situation whereby the contactor C1, makes an electrical circuit or make available the continue
flow of power supply whiles making the contactor C2, de-energized or holding on its contacts
mechanically with the help of an lock inserted in between the two contactors and vice versa.
3.5 THE CONTROL DIAGRAM OF ATS
Figure 3-3 Control diagram of constructed ATS
3.6 THE BASIC OPERATION OF ATS
The basic operation of this circuit is to switch between two sources of power supply. The
figure 3-3 shows control system of an Automatic Change-over Unit also known as Automatic

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Transfer Switch (ATS). Control is to put mechanisms in place to produce a desired output
from a power supply to a load.
Taking the AC lines into consideration, the power supply is taken from the national grid thus
E.C.G. mains, and hence passed through the CB1 then to the mains control switch(MCS).
The supply has to pass through the CB1 to offer protection because of electrical faults such as
short circuit, phase-to-phase, phase-to-ground or earth fault that might have occurred in the
distribution system. This therefore prevents the excessive short circuit current from flowing
into the control system which of course, is much greater than that of the nominal operating
current of the relays, contactors, etc used in this control system.
Therefore, when the mains control switch is closed an electrical power is fed to the on delay
relay (T1) which is energized when the time set on it elapses thereby serving as means of
preventing poor power fluctuation from causing damage to the equipment. After energizing
the coil, closed it contacts manually before through a normally closed (NC) contact of the
relay, R1. From the control circuit, R1 closes to supply power to the contactor, MK through a
NC of the relay, R1. This results in the lighting of the lamp R to indicate that circuit is
complete.
With the same supply from the utility power source, an electrical power is passed through
the CB2; the normal opened, NO, of the R2. However, the positive terminal of the battery of
the generator is connected to R2 through an auto-switch to signal the generator to start in the
event of power failure from ECG. When taking into consideration the stand-by power plant
lines, the same phase is taken as the supply voltage, depending on the time set on T2 after its
coil has energized and closed, then an electrical power will be delivered to the coil of the
relay, R3. The supply voltage through CB3, the NC of R3 supplies power to the contactor,

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GK as result of R3 energizing and making electric circuit. The lamp G comes on as soon as
the C2 coil is energized and make the power circuit complete. Eventually, R1 and R3 from
the AC lines and stand-by power plant lines respectively provides some kind of electrical
interlock; thus the ability to allow continuous flow of electrical current through the AC lines
contactor whiles preventing or blocking that through the contactor of the stand-by power
plant at the same moment or time.
To add to these, the delay set on T2 is there to allow good and efficient oil circulation
through the engine as well as other parts of the stand-by power plant after starting; for
maximum power output, higher efficiency, reliability and to prolong the lifespan of the stand-
by power plant set and other loads feeding from this supply. The closing of the R2 is to start
engine of the stand-by power plant set with help of the auto switch.

35
Figure 3-4 : A picture showing final constructed ATS

36
CHAPTER FOUR
RESULTS, ANALYSIS AND DISCUSSION
4.1 INSTALLATION OF THE CONSTRUCTED ATS
This equipment has been wired and tested at the workshop. Installing the switch includes the
following procedures:
 Connecting power source and load leads.
 Connecting the stand-by power plant sensing and transfer relay circuits.
Qualified personnel should install, operate and service this equipment. Adhere strictly to local
and national electrical and building codes.
4.2 INSTALLATION PRECAUTION
The following information should be carefully read before attempting to install, operate or
service this equipment.
 Qualified engineers or technicians should carefully read manual before attempting to
install, operate or service this equipment.
 Any AC stand-by power plant that is used for backup power if a normal (utility)
power source failure occurs must be isolated from the normal (utility) power source
by means of an approved transfer switch. Failure to properly isolate the normal and
standby power sources from each other may result in injury or death to electric utility
workers, due to back feed of electrical energy.

37
 Improper or unauthorized installation, operation, service or repair of the equipment is
extremely dangerous and may result in death, serious personal injury, or damage to
equipment and/or property.
 Extremely high and dangerous power voltages are present in an installed transfer
switch. Any contact with high voltage terminals, contacts or wires will result in
extremely hazardous, and possibly electric shock. Do not work on the transfer switch
until all power voltage supplies to the switch have been positively turned off.
 Jewelry conducts electricity and wearing it may cause dangerous electrical shock.
Remove all jewelry (such as rings, watches, bracelets, etc) before working on this
equipment.
 If work must be done on this equipment while standing on metal or concrete, place
isolative mats over a dry wood platform. Work on this equipment only while standing
on such isolative mats.
SAFETY
Automatic transfer switches are usually safer than manual switches. Before the power is
switched to a generator, it must be completely shut off from the utility line. Failure to do this
can cause a backfeed in to the utility line. This will send additional power through a line that
shouldn‟t‟ be receiving power. It can injure, or even kill, utility workers. An automatic switch
will stop this from happening since it will shut the power down from the utility line before it
switches on the generator. Manual switches will usually have a safety feature in place, but the
auto switches are fool proof.

38
UTILITY COMPANY REQUIREMENTS
Before you install an automatic transfer switch, the local utility company will want to check
the lines, and then ensure it‟s safety even after installation. You need to contact your utility
agency to find out what‟s required.
CONNECTING POWER SOURCE AND LOAD LINES
Make sure to turn off both the utility (normal) and emergency (stand-by) power supplies
before trying to connect power source and load lines to the transfer switch. Supply voltages
are extremely high and dangerous. Contact with such high voltage power supply lines causes
extremely hazardous or electrical shock. Wiring diagrams and electrical schematics are
provided.
All installations must comply with national codes. It is the responsibility of the installer to
perform an installation that will pass the final electrical inspection. The utility supply
connection is made at the circuit breaker terminals. The stand-by power plant supply and
customer load connections are made at the transfer switch mechanism.
Conductor sizes must be adequate to handle the maximum current to which they will be
subjected to. All power cables must enter the enclosure through the below knockouts. If
aluminum conductors are used, apply corrosion inhibitor. If not tightened enough, a loose
connection would result, causing excess heat which could damage the switch base.
Connect power source load conductors to clearly marked transfer mechanism terminal lugs as
follows:
 Connect utility (normal) power source cables.

39
 Connect emergency (standby) source power cables.
 Connect customer load leads
After installation manual operation must be checked before the transfer switch is operated
electrically. To check manual operation, proceed as follows:
 Turn the stand-by power plant‟s auto/off/manual switch to off.
 Turn off both utility (service disconnect circuit breaker) and emergency (stand-by
power plant main line to circuit breaker) power supplies to the transfer switch.
 Turn the stand-by power plant disconnect switch to the off position.
On the stand-by power plant panel, set the auto/off/ manual switch to manual position. The
stand-by power plant should crank and start. Let the stand-by power plant stabilize and warm
up at no-load for at least five minutes. Turn the stand-by power plant disconnect switch to
the on position.
VOLTAGE RATING
Automatic transfer switches for used generators are unique in regards to their electrical
distribution system in that they are one of only a few electrical devices that are designed to
have two unsynchronized power sources connected to it. For example, this could mean that
voltages impressed on one side of the insulation, in the unit, may actually be as high as 960
volts on a 480 volt AC system. A well designed automatic transfer switch will provide
adequate spacing and insulation to cope with the increased voltage stress.

40
It is due to this reason of increased stress on the unit that spacing in transfer switches should
be less regardless of the component used as part of the transfer switch.
The voltage ratings for AC systems are typically 110, 240, 480, 600 volts, single or
polyphase. Standard frequencies are 50 or 60 hertz. Automatic transfer switches can be used
for other voltages and frequencies if required, this also includes DC.
CONTINUOUS CURRENT RATING
The standard expectation of an automatic transfer switch in regards to a continuous load is
that the switch should be able to hold maximum value for three hours or more. Transfer
switches differ widely from other emergency equipment in that they must continuously carry
the current to critical loads, either from the normal source of power or emergency source.
Whereas, a standby engine generator set usually supplies power only during emergency
periods.
Automatic transfer switches for diesel generators are manufactured to meet continuous
current ratings of 30-4000 amperes. Typically, the most commonly used ampere
ratings include 30, 40, 70, 80, 100, 150, 225, 260, 400, 600, 800, 1000, 1200, 1600, 2000,
3000 and 4000 amperes.
Modern transfer switch technology is capable of carrying 100% of the rated current at an
ambient temperature of 40° C. Transfer switches incorporating integral overcurrent protective

41
devices may be limited-to a continuous load current no more than 80% of the switch rating.
In modern switches there are control measures in place to make sure no more than 80% of the
load is continuous. However in older units system failure is a possibility for exceeding 80%.
Project engineers should anticipate future load requirements during the planning process. Not
all projects require forethought into future load requirements however it is generally
advisable to select a transfer switch with a continuous current rating equal to the total of the
anticipated load.
4.3APPLICATION OF ATS
Automatic transfer switch is intended to use only in optional standby systems in accordance
with the national standard. It is also to protect facilities or property where life safety does not
depend on the performance of the system. This automatic transfer switch is purposely
constructed for industrial and commercial applications where standby power is needed.
These are the various application areas for an ATS, such as:
 Air traffic management in airports
 Emergency power in hospital-intensive-care units and diagnostic equipment
 Standby power systems in residential and light commercial applications
 Data and communication centers
 Commercial buildings
 Industrial plants
 Military bases

42
 Power generation plants
 Sewage treatment plants
4.4 MARKET ANALYSIS
The market growth during the forecast period is expected to be high, mainly driven by the
recovering economy and the need for reliable backup power in today‟s competitive business
environment.
The demand for ATS will depend on the growth of the areas where applicable. The
telecommunication and data processing industries are major end-users of ATS and hence
growth in these industries will have a direct impact on the demand for the ATS. The other
end-user sectors such as hospitals, wastewater treatment plants, power generation plants
among others will also contribute to the growth of the ATS market.
The ATS market is dominated by open transition transfer switch and the bypass isolation
transfer switch segments.
Open transition transfer switch is the simplest of the transfer switches that transfers from one
load to the other and the load is offline for the transfer time. It contributes high volume to the
ATS market, as it is less expensive. The bypass isolation transfer switch is used for critical
applications such as hospitals, diagnostic and treatment centers, and wastewater treatment
plants, among others.
The factors that are likely to contribute to the growth of the ATS market include:
 Falling prices

43
 Flexibility and reliability to integrate with different products
 End-users such as hospitals, wastewater treatment plants, agriculture, data centers,
telecommunication, construction, and residential.
 Demand for stand-by/backup power plant
 Growing functionality of the switch
 Efficiency will emerge as a key consideration in the industrial backup market and
peak shaving applications
 Relationship building
 The demand for ATS will also depend on the growth in end-user application areas
4.5 MARKET TRENDS
The major market trends that are being reflected in the ATS industry include the following:
 There are continuous and additions of controls, including value-added functions such
as surge suppression
 Prices are falling due to the combination of more features built for lower cost
 Bundling of the quality power solution
 Consolidated effort in education the end-user about the importance of ATS products
 Offering value-added products that entice the end-user
 Continuous need for stand-by/backup power equipment for critical applications
gaining ground.
End-user sectors contributing to the growth of ATS include:
 Healthcare and wastewater treatment sectors

44
 Agriculture sector is contributing to the growth of ATS due to the need for
standby/backup and is likely to potentially drive market growth for ATS
 Potential end-user sectors that are likely to contribute to the growth include residential
and commercial
 Telecommunication and data centers will drive this market in the later part of the
forecast period.
4.7 TOTAL COST FOR THE CONSTRUCTION OF THE ATS
Table 4-1 Cost Analysis of Materials used
ITEM
NO
DESCRIPTION QUANTITY UNIT
COST
GH¢
TOTAL
AMOUNT
GH¢
1 Circuit breaker – DZA-639(C45N) 3 20 60
2 Contactor 4-pole,Telemecanique
LCID1810M7
2 80 160
3 Switch 2 25 50
4 Relay-60.12 220V AC,Finder 2 45 90
5 12VDC Relay ,OMRON 1 67 67
6 12VDC, Niesol Timer 1 38 38
7 220VAC ,STel Timer 1 48 48
8 Plastic Panel Box 1 57 57

45
9 1.5mm2
Cable 10 yards 3 30
10 Panel Indicating Lamps 2 30 60
TOTAL COST GH¢ 660
CHAPTER FIVE
CONCLUSIONS AND RECOMMENDATIONS
5.1CONCLUSION
The various test carried out and the results obtained demonstrate that the Automatic Transfer
Switch achieved its purpose for which it was designed and constructed. The system worked
accordingly to specification and quite satisfactory, the Automatic Transfer Switch is
relatively affordable and reliable. It is easy to operate and provide a high level of power
supply in the event of power outages. Finally, it reduces stress associated with the use of
manual change-over. It can therefore be concluded that, the use of Automatic Transfer Switch
is very essential when quicker response of circuit is involved.
5.2RECOMMENDATION
The ATS manufacturer need to be constantly equipped with the latest equipment or
technology been introduced in the market. This would help them in assessing their product
quality and capability and if need to be improve it to suit new equipment requirement. They

46
should constantly work towards designing and manufacturing quality device that have high
features and performance capabilities in order to meet the end-user needs and requirement.
Current technological advancement in the ATS markets is evolutionary, and the market is
moving forward owing to more application and manufacturing advancement.
It also recommended that the manufacturers of ATS should have the end-users consideration
or thoughts at heart in order for their product to suit the increasing demand for ATS on the
market.

47
REFERENCES
Books
[1] Graf, R. F., (1997), Modern Electronics Dictionary, (Pg 132- 133).
[2] Duncan, T., (2001), Success in Electronics, 2nd
ed., (Pg 83-87).
[3] Sinclair, I., (2003), Practical Electronics Handbook, 4th
ed., (Pg 26-30).
Website
[5] http://www.howstuffworks.com
[6] http://www.wikipedea.com
[7] http://www.google.com

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