Aroso Emmanuel A. - IT Technical Report.pdf

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A
TECHNICAL REPORT
ON
STUDENTS’ INDUSTRIAL WORK EXPERIENCE SCHEME (SIWES)
UNDERTAKEN AT
NIMBLES ENGINEERING COMPANY LTD,
IBADAN, OYO STATE, NIGERIA
FROM JULY, 2019 TO DECEMBER, 2019
MADE BY
AROSO EMMANUEL ADEDEJI
CPE/15/2399
SUBMITTED TO
THE DEPARTMENT OF COMPUTER ENGINEERING,
SCHOOL OF ENGINEERING AND ENGINEERING TECHNOLOGY,
FEDERAL UNIVERSITY OF TECHNOLOGY, AKURE
ONDO STATE, NIGERIA
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD
OF THE DEGREE OF BACHELOR OF ENGINEERING (B.ENG)
IN COMPUTER ENGINEERING
FEBRUARY, 2020.

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CERTIFICATION
This is to certify that this report is a detailed report of the Student Industrial Work Experience Scheme
undertaken by AROSO EMMANUEL ADEDEJI with matriculation number CPE/15/2399 at NIMBLES
ENGINEERING COMPANY LIMITED for a period of six months and has been prepared in accordance
to regulations guiding the preparation of reports in the Department of Computer Engineering, Federal
University of Technology, Akure, in partial fulfilment of the requirements for the award of Bachelor of
Engineering (B. Eng.) in Computer Engineering.
….……………………… ….…….……………………………..
Student’s Signature/Date SIWES Coordinator’s Signature/Date

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ACKNOWLEDGEMENT
I am grateful, first and foremost, to almighty God for his grace, strength and knowledge, which made it
possible for me to commence and finish my SIWES program successfully.
My utmost and heartfelt gratitude goes to my parents for their actions during the course of my education in
life; Mr David Aroso for his constant and invaluable support both financially and morally, and Mrs
Oluwakemi Aroso for her prayers and encouragement. You shall reap infinite fruits from the seeds you
labored to sow in the name of JESUS. I also appreciate my brothers and sisters for their love and assistance
during the period of my training.
I would also like to express my special thanks to my department father and role model Mr Ogunti and my
beloved mother and HOD Mrs Dahunsi and the entire Staff of this thriving department for imparting me
adequately to survive in the corporate world.
My most profound appreciation goes to my IT Supervisor, who out of his busy schedule gave me his time
and was patient enough to painstakingly guide me on how to prepare and write this project. May God bless
and reward you abundantly sir.
I would not forget my energetic supervisor, Mr. Oladipupo Seun for his unflinching support till date, and
also Mr. Hakeem, the Human Resources Manager of Nimblescorps, the entire staff and my colleagues at the
company (Blessing, Abiodun, Peace, and Joseph). May God bless you all and reward you abundantly.

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DEDICATION
This report is dedicated to GOD almighty, and my hardworking parents; Mr and Mrs Aroso, for their
enduring support and contributions in my life.

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ABSTRACT
The Students’ Industrial Work Experience Scheme (SIWES) is a scheme that was set up to enhance and
expose students to acquire adequate and relevant skills that would enable them to perform effectively in their
future place of work and assignment. It also exposes students to work methods and enrich their experiences
in acceptable methods of handling equipment and machinery that may not be available in the education
institution. It is also aimed at exposing students to people from all works of life, hence enhancing their
communication skills and ability to interact with people after graduation. This report is a summary of the
knowledge and experiences gained during my Students Industrial Work Experience Scheme (SIWES),
which was done at Nimbles Engineering Company Ltd, Ibadan. Throughout my SIWES period, I worked at
the Automation, Electrical and Networking sections where I was exposed to such things as PLC, HMI,
contactors, industrial star delta configuration, VFDs, network configuration,network routers and switches.
The training has afforded me the opportunity to be exposed and learn from my colleagues and other
individuals within and outside the organization.

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CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE STUDENTS INDUSTRIAL WORK EXPERIENCE SCHEME
(SIWES)
In the early stage of science and technology education in Nigeria, students were graduating from their
respective institutions without any technical knowledge or working experience. There was a growing
concern among industrialists that graduates of institutions of higher learning lacked adequate practical
background studies necessary for employment in industries. Thus, the employers were of the opinion that
the theoretical education going on in higher institutions was not responsive to the needs of the employers of
labour. It was in this view that students undergoing science and technology related courses were mandated
for training in different institutions in view of widening their horizons so as to enable them have technical
knowledge or working experience before graduating from their various institutions.
1.2 HISTORY OF SIWES
The Student Industrial Work Experience Scheme (SIWES) was established by the Industrial Training Fund
(ITF) in 1973 to enable students of tertiary institutions have technical knowledge of industrial work based on
their course of study before the completion of their program in their respective institutions. The ITF solely
funded the scheme during its formative years, but as the financial involvement became unbearable to the
Fund, it withdrew from the Scheme in 1978. The Federal Government handed over the scheme in 1979 to
both the National Universities Commission (NUC) and the National Board for Technical Education (NBTE).
Later the Federal Government in November 1984 reverted the management and implementation of the
SIWES to ITF and it was effectively taken over by the Industrial Training Fund in July 1985 with the
funding being solely borne by the Federal Government.
1.3 SIGNIFICANCE OF SIWES
The scheme was designed to expose students to industrial environment and enable them develop
occupational competencies so that they can readily contribute their quota to national, economic and

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technological development after graduation. The major benefit accruing to students who participate
conscientiously in Students Industrial Work Experience Scheme (SIWES) are the skills and competencies
they acquire. The relevant production skills remain a part of the recipients of industrial training as life-long
assets which cannot be taken away from them. This is because the knowledge and skills acquired through
training are internalized and become relevant when required to perform jobs or functions.
1.4 OBJECTIVES OF SIWES
The Industrial Training Funds policy Document No. 1 of 1973 which established SIWES outlined the
objectives of the scheme. The objectives are to:
i. Provide an avenue for students in higher institutions of learning to acquire industrial skills and
experiences during their course of study.
ii. Prepare students for industrial work situations that they are likely to meet after graduation.
iii. Expose students to work methods and techniques in handling equipment and machinery that may
not be available in their institutions.
iv. Make the transition from school to the world of work easier and enhance students’ contacts for later
job placements.
v. Provide students with the opportunities to apply their educational knowledge in real work situations,
thereby bridging the gap between theory and practice.
vi. Enlist and strengthen employers’ involvement in the entire educational process and prepare students
for employment in Industry and Commerce.
1.5 BODIES INVOLVED IN THE MANAGEMENT OF SIWES
The major bodies involved are: The Federal Government and the Industrial Training Fund (ITF). Other
supervising agents are: National University Commission (NUC), National Board for Technical Education
(NBTE), National Council for Colleges of Education (NCCE), Employers of Labour and Institutions.

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The functions of these agencies above include among others to:
a) Ensure adequate funding of the scheme
b) Establish SIWES and accredit SIWES units in the approved institutions
c) Formulate policies and guidelines for participating bodies and institutions as well as appointing
SIWES coordinators and supporting staff.
d) Supervise students at their places of attachment and sign their log-books and IT forms.
e) Vet and process student’s log-book and forward same to ITF Area office.
f) Ensure payment of allowances to the students and supervisors.
Therefore, the success or otherwise of the SIWES depends on the efficiency of the Ministries, ITF,
Institutions, Employers of labour and the general public involved in articulation and management of the
program. It is pertinent to mention that the scheme is aimed at promoting the much-desired technological
know-how for the advancement of the nation. This laudable scheme among others will surely develop the
much-needed well-skilled and articulated labour force required to build an indigenous self-reliant economy
envisaged for Nigeria.
1.6 PARTICULAR ITF OFFICE VISITED
During the course of my training, I visited the ITF Ibadan Area Office located at Queen Elizabeth Road
Near PHCN Office, Agodi Total Garden, Oyo State. This is where I submitted my SCAF form and had my
logbook signed.
1.7 OBJECTIVES OF THE REPORT
The objectives of the SIWES report are;
a) To put into writing all the practical knowledge and experience acquired during the course of the
industrial training.
b) To prove that I actually participated in the SIWES training.
c) To keep the record for future use or reference.

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d) To fulfill the requirement for bachelor degree in Computer Engineering.
e) To contribute to the body of knowledge and to enhance the understanding of other writers about a
similar or same job.
1.8 THE LOGBOOK
The logbook issued to student on attachment by the institution was used to record all daily activities that
took place during the period of attachment, and it was checked and endorsed by the industry-based,
institution-based supervisors and ITF during supervision.
1.9 RELEVANCE OF SIWES PROGRAMME
My academic work was paramount to the experience I gained from both networking and electrical motor
control systems, because it gave me real basics of theories and as a computer engineer, understanding these
theories was really important because it’s what makes the difference between someone who read computer
engineering and someone one who attended a road side computer schools as system technician.
The industrial experience scheme is an opportunity to work and have the real practical skills needed. The
academic work serves as a platform to know and understand the components, the various aspects, the
theories, laws, principles, techniques and diverse areas of computer engineering which serves as the basis for
understanding what would be done practically as well as selecting the area of specialization in accordance
with the choice of company to work with during the SIWES training. My academic work made me to
understand what I did well during my IT because some terms were used during my training of which were
not explained in details but my academic knowledge made me understand what was being taught. For
example, application of EEE405 (Communication Systems) in understanding the encoding scheme used in
the Physical layer of OSI model to transmits bits from a computer systems to another, CSC101 (Introduction
to Computing Systems), CPE401 (Computer Architecture and Organization) and EEE307 (Electrical
Machines I) assisted in understanding and troubleshooting hardware problems and electric control systems
respectively.

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CHAPTER TWO
2.0 COMPANY PROFILE
2.1 BACKGROUND OF NIMBLES ENGINEERING COMPANY
Nimbles Engineering Company Limited (NEC) is a modern technology-driven company, and was
established in January 15, 2015 by Mr. Bamidele Audu and by Mr. Valentine Bright. It has two branches
located at Suite 4, Drugfield building, adjacent Yunsol Oil gas station, Akala-Expressway,
Oluyole-Extension, Ibadan, Oyo State and 290A Ajose Adeogun, Victoria Island, Lagos. NEC is an
engineering firm that provide technological solutions and support services in Industrial Automation, Home
Automation, Electrical and Control systems as well as IT infrastructure to Oil and Gas, manufacturing,
process and communication industries, and management. The company’s core business is more on
automation (Home and Industrial), networking, hardware repairs and the maintenance and servicing of
industrial machines for manufacturing companies in Nigeria. The company is also into building of industrial
panels for companies and installation of the panels plus its full repairing and PLC programming.
Its team of highly skilled and experienced engineers and business domain specialists offer innovative
solutions to various key industries with a particular focus on Engineering and Technology. They act as a
think tank to collectively craft solutions that make business technology work for their clients and themselves,
and keeping to their core values.
2.2 SERVICES PROVIDED BY NIMBLES ENGINEERING COMPANY
With a team of seasoned technology specialists and dedicated engineers, the company offer the following
services which include:
i. Embedded Systems Engineering
ii. Electrical Services
iii. Home Automation
iv. Industrial Automation
v. Panel Design
vi. Networking

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vii. Security Technologies
viii. Training
2.3 HISTORY OF THE COMPANY
It was established in the year 2015, but before that, they have been operating for five years under the name
and building of a different company. As at then, the company had just a company which was situated in
Ibadan. The company functioned more as a company providing electrical and industrial automation services.
As at 2018, the company has grown financially and substantially providing much more various services and
building projects. Towards the end of the same year, it opened a new and bigger office in V.I. at Lagos, and
moved most of their properties and activities over there.
2.4 ORGANIZATIONAL STRUCTURE OF THE COMPANY
Fig 2.0: The Company’s Organogram

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2.5 OBJECTIVES OF THE COMPANY
2.5.1 VISION
To provide unrivalled customer experience using advances in technology to make living better.
2.5.2 MISSION
To continually improve on quality of service delivery and ensuring that the best of standards is provided to
our customers at all time.
2.6 WORK EXPERIENCE GAINED
During the industrial training program. I gained a lot in the company which has opened and widen my
reasoning about automation in general. The under listed points of experiences are what I took away from the
company.
a) ฀ Programming a PLC (programmable logic controller)
b) ฀ Wiring and maintenance of a PLC.
c) ฀ Repairing of a VFD (variable frequency drive).
d) ฀ Programming of a VFD (variable frequency drive).
e) ฀ Wiring of the VFD (variable frequency drive) in line with the PLC.
f) ฀ Networking of computers in general.
g) ฀ Usage of simulation software: GX Developer, WinCC Flexible, Tesla SCADA, Cisco Packet
Tracer.
h) ฀ Configuration of switches and routers using the hyper-terminal, TELNET and Putty.
i) ฀ Creation of a massive network areas.
j) ฀ Usage of Electrical simulation software such as EKTS for electric motor controls.
2.7 INSTRUMENTS USED IN THE LABORATORY OF THE COMPANY
There are different types of instruments used in the Laboratory for different or the same purposes which can
be grouped according to the way they are used. Some instrument used in the laboratory includes the
following; Relays, Contactors, Wires, Buzzers, LED, Switches, Sensors, Screw drivers, Pliers, Overload
relays, Circuit breakers, PLCs, HMIs, etc.

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According to the way they are used, the instruments can be grouped as both peripheral and main instruments.
The peripheral instruments include; screw drivers, wires, pliers, The main instruments include; sensors,
switches, limit switch, emergency stop switch, terminal point box, 24Vdc relay switch, overload relays,
buzzers, contactors, LEDs, PLCs and so on. The main instruments can also be sub divided into input and
output devices.
The device used mainly by the company by which all other devices rely on is the PLC.
Plate 2.0: A timer-relay Plate 2.1: A Relay Plate 2.2: Pushbutton LEDs
Plate 2.3: 1P,2P, 3P Circuit breaker Plate 2.4: A contactor Plate 2.5: A
Pushbutton

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CHAPTER THREE
3.0 KNOWLEDGE AND WORK EXPERIENCE GAINED
3.1.0 NETWORKING AND SECURITY SYSTEMS
Network:At the most basic level, a network is defined as a group of systems interconnected to share
resources.
Networking: Is the sharing of resources and services between interconnected devices.
A network, also referred to as a data network or a computer network, consists of a set of devices connected
together through a medium in order to be able to exchange data between themselves. These devices create a
network using their respective network interfaces. Some devices may use a single network interface, other
devices may be connected to the network via multiple interfaces.
The basic function of a computer network is to make it possible for geographically remote end users to
communicate. We need networking for the following; file sharing, network gaming, audio/video calls, file
transfer, database access, printer sharing, hardware sharing, surfing the web and so on.
3.1.1 THE STRUCTURE OF COMPUTER NETWORKS
A typical computer-communications network comprises hosts, users and a subnet that connects them.
Communication networks that provide connections between a computer and another (or a terminal) can be
divided into two basic types:
a) Connection-oriented (or circuit-switched): It operates by forming a dedicated connection or circuit
between two points. The telephone system uses this type of technology - a telephone call will establish a
connection from the caller’s phone through local switching office, across trunk lines, to a remote
switching office, and finally to the destination phone. The main advantage of this network is guaranteed
network capacity. One disadvantage is circuits cost are fixed, independent of use.
b) Connectionless (or packet-switched): Data to be transferred across a network is divided into small
pieces called packets that are multiplexed onto high capacity inter-machine connections. The chief
advantage is that multiple communications among computers can occur concurrently. The disadvantage
is that whenever the network activity increases, a particular pair of communicating computers receive
less of the network capacity.

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Despite the potential drawback faced, connectionless networks have become extremely popular, the Internet
has chosen it’s approach to switching at the network layer. The motivations for adopting packet switching
are cost and performance, and since it allows multiple computers to share the network bandwidth, fewer
connections are required and cost is kept low. Engineers have been able to build high-speed network
hardware, hence, capacity is not usually a problem.
3.1.2 NETWORK BASICS
3.1.2.1 COMPONENTS OF A NETWORK
A network can be as simple as two PCs that are connected by a wire or as complex as several thousand
devices that are connected through different types of media. I observed that the elements that form a network
can be roughly divided into three categories: devices, media and services. Devices are interconnected by
media. Media provides the channel over which the data travels from source to destination. Services are
software and processes that support common networking applications.
3.1.2.1.1 NETWORK DEVICES
They can be further divided into endpoints and intermediary devices:
A. Endpoints: End-users devices fall under this category and include PCs, laptops, tablets, mobile phones,
game consoles and television sets (Smart-TV). Endpoints are also file servers, printers, sensors, cameras,
smart home components and so on. I learnt many end devices are now virtualized, this is made possible
due to Virtualization technology. Virtualization is commonly applied to servers.
B. Intermediary devices: An intermediary device is any networking device that provide connectivity and
work behind the scenes to ensure that data flows across the network. Intermediary devices connect the
individual hosts to the network and can connect multiple individual networks to form an internetwork.
Examples of intermediary network devices are:
a) switches and wireless access points (network access)
b) routers (internetworking)

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c) firewalls (security).
During my stay at NEC, I was able to interact with the following devices:
a) Server: In general, a server is a computer that provides shared resources to network users called clients.
Servers are typically powerful computers that run the software that manage a network. A server is
usually dedicated to a task.
Plate 3.0: A server
b) Network Interface Card (NIC): A NIC provides the hardware interface between a computer and a
network, which means a computer must have at least one NIC to participate in a network. This device
provides the physical, electrical, and electronic connections to the network media. Today, almost all
new computer motherboards have built-in NICs which were originally available as expansion cards.
Plate 3.1: An expansion card NIC
Some NIC cards are meant for wired networks (e.g. Ethernet) while others are for wireless networks ( e.g.
Wi-Fi). Every NIC has a 48-bit globally unique identifier called as MAC address burned into its ROM chip,
which is used to deliver Ethernet Frames (packets) to a computer. The NIC driver software passes the data
between the OS and the NIC.

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c) Network Switches and Hubs: Both are LAN devices used to interconnect multiple devices. The hub
repeats all received electrical signals and floods out through all other ports (except the incoming port).
It uses half-duplex algorithm called CSMA/CD to avoid collisions when forwarding electrical signals.
Plate 3.2: A Cisco Catalyst Switch Plate 3.3: A network hub
Switches segment each link connected to it as a separate collision domain, hence, do not have half-duplex
restrictions like hubs. Switches are called intelligent devices because they have the knowledge of ethernet
frames and MAC addresses, and make decisions based on these to forward data to it’s destination only
They both possess two types of ports: MDI and MDI-X. The MDI-X port has it’s wiring crossed and is used
to connect to devices with an MDI port such as PC, server, router, printer, firewall and so on using a
straight-through cable.
Both devices come in two versions: managed and unmanaged. They also use LEDs to indicate certain
connection conditions. I observed that the LEDs show current status of the device such as duplex mode,
speed, activity, errors/collision and so on.
d) Network Router: It’s primary function is to route data packets to other networks, instead of only the
local computers. When a data packet comes into one of the links, the router reads the address
information in the packet to determine its ultimate destination. Then, using information in its routing
table or routing policy, it directs the packet to the next network on its journey.
Essentially, a router bridges the gap between other networks and gives a network access to more features
such as firewall, VPN, QoS, traffic monitoring and much more.

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Plate 3.4: A Cisco 1800 series ISR Router
3.1.2.2 CLASSIFICATION OF NETWORKS
From my experiences gained at NEC, I discerned that a network can be classified into three different
categories: by geography, topology and architecture.
3.1.2.2.1 CLASSIFYING NETWORKS BY GEOGRAPHY
The fundamental differences among these are distance coverage, data rates,transmission delay, media and
error rates.
i. Personal Area Network (PAN): It is a network that exist around an individual within a single building
e.g. between two Bluetooth devices/smartphones.
ii. Local Area Connection (LAN): It is owned by a single organization and physically located in the same
building or within a group of buildings. A LAN is useful for sharing of resources such as printers, file
servers, flash drives, CD-ROM, scanners etc.
iii. Campus Area Network (CAN): is a computer network of computer devices or LANs connected
together within a wide campus.
iv. Metropolitan Area Network (MAN): It interconnects or links multiple LANs by using high bandwidth
backbone inside a large city or metropolitan region covering up to 40km.
v. Wide Area Network (WAN): is a network that exists over a large-scale geographical area. A WAN
connects different smaller networks, including LANs and MANs. WAN implementation can be done
either with the help of the public transmission system or a private network. The Internet is a WAN.

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vi. Global Area Network (GAN): refers to a network composed of different interconnected networks that
cover an unlimited geographical area. The term is loosely synonymous with Internet, which is
considered a global area network. The most sought-after GAN type is a broadband GAN, which is a
global satellite Internet network that uses portable terminals for telephony.
Because the cable length in a LAN do not generally exceed about 3km, it transmits data at a much higher
speed than a WAN which may extend across entire continents and have intercontinental links. Same trend
occur for error rates and transmission delays in both.
3.1.2.2.2 Classifying Networks By Topology
Network Topology refers to the arrangement by which computers are connected to each other. Topologies
use either a point-to-point or multipoint connection scheme.
A connection scheme indicates how many devices are connected to a transmission media segment or an
individual cable.
An example of a point-to-point connection scheme is a modem or printer connected to computer, direct
cable connection between two computers.
An example of a multipoint connection scheme is a star or bus topology network.
3.1.2.2.2.1 Physical vs. Logical Topologies
Physical topology refers to the way in which a network is laid out physically, that is, the actual layout of the
wire or media (cabling). Two or more devices connect to a link; two or more links form a topology.
Two networks might have the same physical topology, but distances between nodes, physical
interconnections, transmission rates, or signal types may be different.
Logical topology defines how the hosts access the media to send data. It shows the flow of data on a
network. The two most common types of logical topologies are broadcast and token passing.
A physical topology can be further categorized into two types: LAN and WAN (site-to-site) topologies.

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1. LAN Network Topologies
i. Bus Topology: It consists of a main run of cable(s) that transmit data to all the nodes on the
network. Terminators at the end of the cable prevent signals from reflecting back to the sender.
Break or faulty piece of cable anywhere on the segment prevents all the computers on the
segment from being able to communicate.
ii. Ring Topology: Each node is connected to its two adjacent nodes and data is circulated around
the closed ring. Each device in the ring incorporates a repeater, which regenerates the bits of a
signal intended for another device and passes them along.
iii. Mesh Topology: There is multiple data paths between network devices or nodes. It require
extra cables, which makes it costly, and it is very complex and difficult to manage. It is not
commonly used these days.
iv. Star Topology: This is the most widely used network topology. It involves the use of a central
intermediary device (e.g. a network switch/router) to connect among all the endpoints.
v. Hybrid Topology: It is a mixture of different topologies. Examples include a star-ring
network.
Fig 3.0: LAN network topologies

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2. Site-to-Site Network Topologies
i. Hub-and-spoke WAN Topology: Large enterprises have multiple offices (physical sites) in different
geographical locations. Normally, Internet Service Providers (ISPs) provide network connectivity
solutions to connect multiple physical sites in different geographical locations. In this network topology,
one physical site acts as “Hub”, while other physical sites act as “spokes”. The network communication
between two spokes always travel through the hub, since they are connected to each other via Hub site.
Fig 3.1: Hub-and-spoke network
ii. Tree Topology: It has a root node and all other nodes are connected to it forming a hierarchy, it is also
called hierarchical topology.
3.1.2.2.3 CLASSIFYING NETWORKS BY ARCHITECTURE
By architecture means where do the clients get their resources such as a dedicated server on a network, or
from one another.
i. Client-Server Network: Shared resources are placed on a dedicated server that manage a
given resource on behalf of clients sharing the resources. Examples of servers include file
server, web server, printer server, DNS server, DHCP server, optical disk server.
ii. Peer-to-peer Network: Computers communicate with any other networked computers on an
equal or peer-like basis without going through an intermediary, such as a server or dedicated

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host. Resources are located at terminals and system administration is largely left up to the
users.
Fig 3.2: Client-server network Fig 3.3: Peer-to-peer network
3.1.2.3 NETWORK REFERENCE MODELS
A reference model is a conceptual blueprint of how communication should take place. For a network to
work correctly, the various devices and software must follow rules which come in the form of standard and
protocols.
3.1.2.3.1 HISTORY OF REFERENCE MODELS
When networks first existed, computers could only communicate with computers from the same
manufacturer. So, if a company bought computers from three vendors, network engineers often had to create
three different networks based on the networking models created by each company, and then somehow
connect those networks, making the combined networks much more complex. The ISO took on the task to
create an open, vendor-neutral networking model that would aid competition and reduce complexity by
developing the OSI model. Years later, the DoD released their TCP/IP networking model for the same
purpose.
Presently, TCP/IP dominates and while proprietary networking models still exist, they have mostly been
discarded in favor of TCP/IP.

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3.1.2.3.2 THE OSI REFERENCE MODEL
The OSI (Open Systems Interconnection) model is a reference model for how applications communicate
over a network. A reference model is a conceptual framework for understanding relationships. The purpose
of the OSI reference model is to guide vendors and developers so the digital communication products and
software programs they create can interoperate, and to facilitate a clear framework that describes the
functions of a networking or telecommunication system. Most vendors involved in telecommunications
make an attempt to describe their products and services in relation to the OSI model.
The main concept of OSI model is that the process of communication between two endpoints in a network
can be divided into seven distinct groups of related functions, or layers. The model is composed of seven
ordered layers: physical (layer 1), data link (layer 2), network (layer 3), transport (layer 4), session (layer 5),
presentation (layer 6), and application (layer 7).
3.1.2.3.2.1 ORGANIZATION OF THE OSI LAYERS
The seven layers can be thought of as belonging to three subgroups:
A. The Network support layers: Layers I, 2, and 3; they deal with the physical aspects of moving data
from one device to another (such as electrical specifications, physical connections, physical addressing,
and transport timing and reliability).
B. The Transport layer: Layer 4; it links the two subgroups and ensures that what the lower layers have
transmitted is in a form that the upper layers can use.
C. The User support layers: Layers 5, 6, and 7; they allow interoperability among unrelated software
systems.
The upper OSI layers are almost always implemented in software; lower layers are a combination of
hardware and software, except for the physical layer, which is mostly hardware.
3.1.2.3.2.2 FUNCTIONS OF EACH LAYER

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Summary of the functions of each layers is given below:
1. Application - contains protocols used for process-to-process communications. Basically, it provides
functions for users or their programs. This layer does not represent user applications on a system
such as a web browser or spreadsheet, but defines the processes that enable applications to use
network services.
2. Presentation - it’s basic function is to convert the data intended for or received from the application
layer into another format, so that it can be transported across the network. Some common data
formats handled by this layer include: Graphics files (JPEG, PNG), Text and data (ASCII), Sound
/ video (MPEG, MP3). This layer also provides encryption.
3. Session - is responsible for managing and controlling the synchronization of data between
applications on two devices. It does this by establishing, maintaining, and breaking sessions.
Whereas the transport layer is responsible for setting up and maintaining the connection between
the two endpoints, the session layer performs the same function on behalf of the application.
4. Transport - responsible for host-to-host communication and making sure the segments received from
the upper layer reaches their destination. It performs error correction, reliable delivery of data ,
segmentation and reassembly of the data. It uses TCP and UDP protocols.
5. Network - the primary responsibility of this layer is routing - providing mechanisms by which data
can be passed between networks. It does so by using logical addresses such as IPv4, IPv6 and
Appletalk.
6. Data Link - is responsible for communication in a LAN using physical address called MAC address.
It has two distinct sublayers: MAC and LLC layers.
7. Physical - describes the mechanical, electrical, functional, and procedural means to transmit
bits/signals across physical connections.

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Fig 3.4: Encapsulation of data from layer-to-layer
3.1.2.3.3 THE TCP/IP SUITE
The TCP/IP suite is a set of protocols used on computer networks today (most notably on the Internet). It
provides an end-to-end connectivity by specifying how data should be packetized, addressed, transmitted,
routed and received on a TCP/IP network. This functionality is organized into four abstraction layers and
each protocol in the suite resides in a particular layer.
The TCP/IP suite is named after its most important protocols, the Transmission Control Protocol (TCP) and
the Internet Protocol (IP).
Fig 3.5: Comparison of OSI vs TCP/IP and their corresponding protocols

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3.1.2.4 TRANSMISISON MEDIA
The type of interface(s) used by a device to connect to a network depends on the medium being used to
connect. A wireless network interface is used to connect to a network over-the-air using a standard such as
IEEE 802.11. There are various types of wired mediums in use today, the most common of which follows
the IEEE 802.3 standard (Ethernet). Most devices that have a wired network interface will have at least one
Ethernet interface.
3.1.2.4.1 WIRED MEDIA
These are media which require the use of wires, lines and cables to transmit communication signals or data
(bits). During my industrial training at NEC, I encountered majorly three different types of wired network
media namely: coaxial cables, twisted cables and optical fibre cables.
1. Coaxial Cables
A coaxial cable is an alternative for protecting data from noise. Coaxial cables do not produce external
electric and magnetic fields and are not affected by them. This makes them ideally suited, although more
expensive, for transmitting signals.
Fig 3.6: Coaxial cable
Coaxial cables is outdated as an Ethernet technology and have been replaced by twisted pair Ethernet, which
is easier and cheaper to install.
2. Twisted Pair Cables
This is so called due to the fact that wire pairs in the actual cable are twisted together. When electrical
current passes over any wire, it creates electromagnetic interference (EMI) that interferes with the electrical

22
signals in nearby wires, including the wires in the same cable (EMI between wire pairs in the same cable is
called crosstalk). Twisting the wire pairs together helps cancel out most of the EMI, so most networking
physical links that use copper wires use twisted pairs.
There exist two types of twisted pair cables: Shielded Twisted Pair and Unshielded Twisted Pair (UTP). The
shielded twisted pair cable gives better network strength while UTP cable provides faster transfer rate. In
most situations, UTP cables get the job done just fine and at the same time cost less than the shielded type.
Hence, why UTP is popular and usually used among the two.
In a twisted pair cable, there are eight copper wire that are coated with different colours; the colours are
mix/orange, orange, mix/blue, blue, mix/green, green, mix/brown and brown.
Fig 3.7: Unshielded pair Fig 3.8: Shielded pair
3. Optical Fibre Cables
Fiber-optic cabling uses glass as the medium through which light passes, varying that light over time to
encode 0s and 1s. It transmits optical pulses instead of electric signals, so it does not get interfered by
electrical interference.
Fiber-optic cables use fiberglass, which allows a manufacturer to spin a long thin string (fiber) of flexible
glass. A fiber-optic cable holds the fiber in the middle of the cable, allowing the light to pass through the
glass, which is a very important attribute for the purposes of sending data.
Although sending data through a glass fiber works well, the glass fiber by itself needs some help. The glass
could break, so the glass fiber needs some protection and strengthening. The three outer layers of the cable
provides the needed protection for the interior of the cable and make the cables easier to install and manage.

23
A light source, called the optical transmitter, shines a light into the core. Light can pass through the core;
however, light reflects off the cladding back into the core.
Fig 3.9: Components of a Fibre-Optic Cable
Optical fibre come in two types:
i. Multi-mode Fibre: Multi-mode improves the maximum distances over UTP, and it uses less expensive
transmitters as compared with single-mode.
Fig 3.10: Transmission on Multimode Fiber with Internal Reflection
ii. Single-Mode Fibre: Single-mode allows distances into the tens of kilometers, but with slightly more
expensive hardware.
Fig 3.11: Transmission on Single-Mode Fiber with Laser Transmitter

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3.1.2.4.2 WIRELESS MEDIA
To fully explore the wireless added dimension, communication system designers have sought to use wireless
media to reduce infrastructure cost and complexity, when compared to wired communication systems. There
is no need to construct miles of telephone line poles or cable trenches.
I learnt that the wireless devices use radio frequencies (RFs) that are radiated into the air from an antenna
that creates radio waves. Wireless LANs run half-duplex communication, similarly as Ethernet hubs, due to
the fact that everyone is sharing the same bandwidth. Hence, only one user can communicate at a time.
There are various kinds of IEEE 802.11 (also called the Wi-Fi Alliance) wireless standards that have been in
use in a LAN, each offering new features which each updates:
Table 3.1: IEEE 802.11 Wireless Standards
IEEE Standard Frequency Range Max. Speed Max. Distance Capacity Per Cell
IEEE 802.11a 5 GHz 54 Mbps 200 ft 15 users
IEEE 802.11b 2.4 GHz 11 Mbps 350 ft 25 users
IEEE 802.11g 2.4 GHz 54 Mbps 300 ft 20 users
IEEE 802.11n 2.4/5 GHz 300 Mbps 230 ft Not definite
IEEE 802.11ac 5 GHz 0.5-1 Gbps 230 ft Not definite
3.1.2.5 ETHERNET CABLING
3.1.2.5.1 ETHERNET LANS
Many types of LANs have existed over the years, but today’s networks use two general types of LANs:
Ethernet LANs and Wireless LANs (WLANs). Ethernet LANs use cables for the links between nodes, and
because many types of cables use copper wires, Ethernet LANs are often called wired LANs. Ethernet LANs
also make use of fiber-optic cabling.
3.1.2.5.1.2 IEEE CABLING STANDARDS

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The Ethernet physical layer standards specifies the name and features of cables used in an Ethernet LAN. So
one should consult it before deciding on products to buy for a new LAN.
Table 3.2: IEEE 802.3 Cabling Standards
Speed Common Name Informal IEEE
Standard Name
Formal IEEE
Standard Name
Cable Type/Max. Length
10Mbps Thin-Wire Ethernet 10Base2 (thinnet) Coaxial/200m
10Mbps Thick-Wire Ethernet 10Base5(thicknet) Coaxial/500m
100Mbps FastEthernet 100Base-T 802.3u Copper (UTP)/100m
1000Mbps GigabitEthernet 1000Base-LX 802.3z Fibre (single-mode)/5000m
1000Mbps GigabitEthernet 1000Base-T 802.3ab Copper (UTP)/100m
3.1.2.5.1.3 ETHERNET PROTOCOLS IN DATA LINK LAYER VS PHYSICAL LAYER
Although Ethernet includes many physical layer standards, Ethernet acts like a single LAN technology
because it uses the same data-link layer standard over all types of Ethernet physical links.
I learnt that whether the data flows over a UTP cable or any kind of fiber cable, and no matter the speed, the
data-link header and trailer use the same format.
While the physical layer standards focus on sending bits over a cable, the Ethernet data-link protocols focus
on sending an Ethernet frame from source to destination Ethernet node.
3.1.2.5.1.3.1 ETHERNET FRAMES
The encapsulated data defined by the Network Access layer is called an Ethernet frame. An Ethernet frame
starts with a header, which contains the source and destination MAC addresses, among other data. The
middle part of the frame is the actual data. The frame ends with a field called Frame Check Sequence (FCS).
The Ethernet frame structure is defined in the IEEE 802.3 standard. Here is a graphical representation of an
Ethernet frame and a description of each field in the frame:

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Fig 3.12 : An Ethernet frame
I. Preamble: informs the receiving system that a frame is starting and enables synchronization.
II. SFD(Start Frame Delimiter): signifies that the Destination MAC Address field begins with the next
byte.
III. Destination Address: identifies the receiving system.
IV. Source Address: identifies the sending system.
V. Type: defines the type of protocol inside the frame, for example IPv4 or IPv6.
VI. Data: contains the payload data. Padding data is added to meet the minimum length requirement for this
field (46 bytes).
VII. FCS (Frame Check Sequence): contains a 32-bit Cyclic Redundancy Check (CRC) which allows
detection of corrupted data.
The FCS field is the only field present in the Ethernet trailer. It allows the receiver to discover whether
errors occurred in the frame. Note that Ethernet only detects in-transit corruption of data; it does not attempt
to recover a lost frame. Other higher level protocols (e.g. TCP) perform error recovery.
3.1.2.5.1.4 FULL AND HALF DUPLEX IN ETHERNET LANS
a) Ethernet Shared Media: It refers to network designs that use hubs, and share the bandwidth. The
devices connected to the hub share the network because they must use CSMA/CD to avoid collisions of
signals, and CSMA/CD enforces rules that allow only one device to successfully send a frame at any
point in time which implies half-duplex communication.

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b) Ethernet Point-To-Point: In a network built with switches, each (point-to-point) link works
independently of the others. Because a switch isolates each link into separate collision domains, a frame
can be sent and received on every point-to-point link in an Ethernet at the same time.
3.1.2.5.1.5 UTP CABLING
Before the Ethernet network as a whole can send Ethernet frames between user devices, each node must be
ready and able to send data over an individual physical link.
3.1.2.5.1.5.1 TRANSMITTING DATA USING TWISTED PAIRS
To better illustrate how Ethernet sends data using electricity, two scenarios are considered as shown below:
First, an electrical circuit is created between two nodes using the two wires inside a single twisted pair of
wires inside a UTP cable. So, the two nodes, using circuitry on their Ethernet ports, connect the wires in one
pair to complete a loop, allowing electricity to flow.
+
Fig 3.13: Creating One Electrical Circuit over One Pair to Send in One Direction
Secondly, following some set of rules called encoding scheme, the transmitting node changes the electrical
signal over time, while the other node, the receiver, using the same rules, interprets those changes as either
0s or 1s. I learnt that Ethernet uses Manchester encoding.
3.1.2.5.1.5.2 METHODS OF UTP CABLING
There are three connection methods for the UTP cable with it’s connector (RJ45) and every method is used
in a certain situation: straight-through , crossover and rolled cables.

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Ethernet twisted pair cable uses two pairs of wires for transmission of data. MDI devices (e.g. PC) transmits
on pins “1” and “2”, and receives on pin “3” and “6”. Knowing this fact, switches and hubs use MDI-X
which reverses the wiring scheme of MDI.
a) Straight-through cable: This cable is used to connect between two devices with different interfaces or
ports. This is achieved through the use of the same color scheme on both ends of a UTP. The color code
used may be either T-568A or T-568B standard.
Fig 3.14: MDI to MDI-X connection Fig 3.15: Straight-through wiring
b) Crossover cable: It connects two devices with the same interface or ports. This cable is made by using
different color schemes on the ends of a UTP cable.
Fig 3.16: MDI to MDI connection Fig 3.17: Crossover wiring
c) Rolled cable: This is a special cable which used to connect a PC or laptop to a router’s console, in case
we need to configure the router directly or perform initial configuration on it.

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Fig 3.18: Rolled cable wiring
3.1.2.5.1.5.3 HOW TO MAKE A CAT 5/6 UTP CABLE FOR TRANSMITTING
STRAIGHT-THROUGH OR CROSSOVER
I learnt that there is various categories of UTP cables: CAT 1 to 8; each with their various capability.
The following are the materials needed to produce an Ethernet LAN UTP cable:
a) Cat 5 cable: One can buy a 1000 feet roll of Cat 5 cable at computer stores and industry supply houses
at an affordable price depending on the quality. Check to make sure that the color-coding on the wires is
easily recognizable.
Plate 3.5: A pack of cat 5 cables
b) RJ-45 Connectors: RJ45 is a standard type of connector for network cables. RJ45 connectors are most
commonly seen with Ethernet cables and networks. RJ45 connectors feature eight pins to which the
wire strands of a cable interface electrically. They usually come in bags of 50, 100 etc. Attention should
be paid to the type of RJ-45 connector being purchased and make sure it is intended for the type of Cat 5
wire you are using. There are two different kinds of RJ-45 connectors, using the wrong kind with the
wrong cable will most likely result in a bad connection

30
c) Crimping tool: Is a tool used to terminate category cables such as CAT1-CAT6 using an RJ-45
connector. A good crimping tool has a pair of wire cutters built in, as well as a blade to strip insulation.
It also might support crimping of other connectors such as RJ-11.
d) LAN cable tester: This is used to test if a category cable has been well terminated, or developed a fault.
e) Diagonal Cutter Pliers: You will need a pair of this to cut the wires in case the crimper does not come
with a built-in wire cutter or failed to cut.
Plate 3.6: RJ-45 connectors Plate 3.7: Crimping tool Plate 3.8: Cable tester
STEPS INVOLVED
Step1: Cut a piece of Cat 5 cable as long as you need. Make sure the cut on each end is clean and straight.
Plate 3.9: A cut cat 5 cable
Step2: Strip about an inch of the insulation off the cable. It is extremely important that you only cut the
plastic insulation or jacket and not the wire. Damaging one of the 8 wires, even if you just nick it or
partially cut it, will ruin your cable.
Plate 3.10: A stripped cable

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Step 3: Untwist the wires and pair similar colors. Sort the 4 pairs of multi-colored wires inside and align
according to preferred wiring standard (color scheme).
Plate 3.11: Untwisted cat 5 cable
Step 4: Prepare wires for RJ-45 connector. Get the wires lined up nice and straight. Then clip off the top
millimeter so that they are all the same length and stick out about half an inch from the insulated part.
Plate 3.12: A lined-up/straightened cable
Step 5: Insert wires into RJ-45 connector.
Plate 3.13: Inserted cable
Step 6: Crimp and test the continuity.
Plate 3.14: Crimping the cable Plate 3.15: Crimped cable Plate 3.16: Testing of the cable

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Using Optical Fiber Cables With Ethernet (Fiber-Optics Cabling)
The distance between Ethernet switches and endpoints in a LAN is unlikely to exceed the maximum cable
length capability of UTP cables, however, there might cases where, in a LAN, fiber cabling is the only way
to go.
To use fiber with Ethernet switches,your switch must have ports (built-in or modular) that supports optical
Ethernet Standard. Two cables are needed to transmit between two devices, one for each direction. Despite
the cost being relatively high when compared with UTP, benefits for using fiber include longer distance,
higher transfer speed and zero risk of EMI and signal emissions.
3.1.2.5.1.6 WIRELESS LAN
I worked with two of the most common wireless LAN technologies namely: Wi-Fi and Bluetooth.
3.1.2.6 RELEVANT TERMS USED IN NETWORKING
Host: A host is the ultimate consumer of communication services. It is a physical network node with an IP
address assigned and they are general-purpose computers. It has a complete network stack from physical
layer to application layer.
Node: It is any device that is active in the network; a node may have only a partial network stack e.g. only
physical layer or only physical to network layer. All hosts are nodes but all nodes are hosts.
Gateway: A device connected to two or more networks, appearing to each of these networks as a connected
host. Thus, it has a physical interface and an IP address on each of the connected network.
Ethernet: It refers to an entire family of standards or technologies for LANs. The Ethernet protocol, also
referred to as IEEE 802.3, has largely replaced competing wired LAN technologies. Ethernet used coaxial
cable as a shared medium. Later, the coaxial cables were replaced by twisted pair and fibre optics links in
conjunction with hubs or switches.

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Collision Domain: This is the part of a network where packet collisions can occur. A collision occurs when
two devices send a packet at the same time on the shared network segment. Collisions are often in a hub
environment, because each port on a hub is in the same collision domain.
Broadcast Domain: It is the domain in which a broadcast is forwarded. A broadcast domain contains all
devices that can reach each other at the data link layer (OSI layer 2) by using broadcast. All ports on a hub
or a switch are by default in the same broadcast domain.
DNS: Domain Name System, is the phone-book of the Internet,
DHCP: Dynamic Host Configuration Protocol,
Firewalls: A firewall is a device that prevents unauthorized electronic access to an entire network. The
term firewall is generic, and includes many different kinds of protective hardware and software devices.
Proxy Server: acts as a gateway between a host and the internet. It’s an intermediary server separating end
users from the websites they browse. Proxy servers data security, network performance and a high level of
privacy.
World Wide Web (WWW): is a collection of interconnected documents and other resources, linked by
hyperlinks and URLs. It is one of the services accessible via the Internet along others including email, video
streaming etc. It is fundamentally a client/server application running over the Internet and TCP/IP intranets.
Internetwork: can be defined as two or more computers (typically LANs) which are connected together,
using network routers. Each network in an internetwork has it’s own network address. The words
internetwork and internet are simply a contraction of the phrase interconnected network, internet should not
be confused with Internet.
Internet: is a worldwide publicly accessible computer network of interconnected computer networks that
transmit data using the standard Internet Protocol (IP) . Internet is such a huge network of several different
interlinked networks relating to the business, government, academic, and even smaller domestic networks,
therefore internet is known as the network of all the other network.

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Intranet: An intranet is a private network that is contained within an enterprise. It may consist of many
interlinked local area networks and also use leased lines in the wide area network. Typically, an intranet
includes connections through one or more gateway computers to the outside Internet. The main purpose of
an intranet is to share company information and computing resources among employees. An intranet can
also be used to facilitate working in groups and for teleconferences.
Extranet: It can be viewed as part of a company’s intranet that is extended to users outside the company.
VPN: In a VPN, Virtual Private Network, private communication between two or more devices is achieved
through a public network in the Internet.
Backbones: are large networks that exist primarily to interconnect other networks.
Network Protocols: are rules and standards that must be followed before any form of communication can
occur over a network. They extend from the electric connection to the network and the format of the
message, all the way to the interaction between application programs that run on different endpoints.
Proprietary protocols are developed by a company while standard protocols are not vendor-specific.
Quality of Service (QoS): The application of QoS is a methodology used to provide optimal performance
for a variety of applications in what is ultimately an environment with finite resources. A well-designed QoS
plan conditions the network to give access to the right amount of network resources needed by applications
using the network, whether they are real-time or interactive applications. If no QoS level is defined, the
network defaults to what is called best-effort service.
3.1.2.6.1 ORGANIZATION THAT GOVERNS NETWORK PROTOCOLS
i. IEEE: The Institute of Electrical and Electronics Engineers regulates the technologies and
protocols used in networks.
ii. IANA: Internet Assigned Numbers Authority, based in the United States, is an Internet-specific
organization that gives out (assigns and allocates) IP addresses in a systematic, organized and
consistent manner that benefits everyone.

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iii. RIR: Regional Internet Registry, is an organization that manages and controls Internet
addresses in a specific region, usually a country and sometimes an entire continent. RIRs
control assigning and distributing IP addresses and domain registrations. The RIRs, as a matter
of fact, do not generate the IP addresses that they themselves allocate, but take the IP addresses
allocated to them by the IANA and handle the next level of allocation. They serve ISPs,
educational institutions, governments, large corporation and organizations.
iv. ICANN: Internet Corporation For Assigned Names And Numbers, is the institution which runs
IANA.
3.1.2.7 IP ADDRESSING AND SUBNET MASK
3.1.2.7.1 IP ADDRESS
An IP address is a long logical address that logically identify a host in a network. The two types of IP
addresses are IPv4 and IPv6. IPv4 is 32-bits and IPv6 is 128-bits.
IPv4 => 192.168.1.10. It contains four octets (8-bits each) divided by using dots “.”
IPv6 => 2001:0DB8:0000:0000:1234:0000:A9FE:133E. It comprises alphanumeric eight octets (16-bits
each) separated by colon “:”.
3.1.2.7.1.1 Functions of IP Addressing
i. For location of a device on the network
ii. It is assigned to allow hosts on one network to communicate to hosts on another network.
Computers do not understand decimal but only binary.
3.1.2.7.1.2 Terms used in IP addressing
i. Bit- A bit is a binary digit, either 0 or 1.
ii. Byte - A byte is eight bits.
iii. Network address - This is a designation used to send packets to a remote network. Examples
are 10.0.0.0, 172.68.0.0, 192.168.10.0

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iv. Broadcast Address - This is the address used to send data to all hosts on a broadcast domain.
When all the host bits are on (‘1’) this is a broadcast address for all hosts, 255 are reserved for
sending broadcast message. E.g. 192.168.10.255.
v. Unicast Address - is an address that identifies a unique node on a network
3.1.2.7.1.3 Classes of IPv4 Addresses
IPv4 which is 32-bits has class ranges from class A-E.
a. Class A: This Class of address can only be between 0 and 127. All 0’s reserved are for default
route and ‘127’ is reserved for troubleshooting –loop back, therefore, Class A valid address
ranges that can be assigned to host on a network is 1-126.
b. Class B: It ranges between 172 – 191.
c. Class C: Class address can only be between 192 – 223.
Note: Class A to C are unicast addresses.
d. Class D: 224-239. It is used for multicasting.
e. Class E: 240-255. It is for research purposes.
3.1.2.7.1.4 PRIVATE IPV4 ADDRESSES
Are introduced in mid 1990s due to depletion of IPv4 addresses. They are used only in internal networks
such as LANs, and must be translated to a public IPv4 to be routable to the Internet.
3.1.2.7.1.4.1 PRIVATE IP ADDRESS BLOCKS
i. Class A: 10.0.0.0 to 10.255.255.255
ii. Class B: 172.16.0.0 to 172.31.255.255
iii. Class C: 192.168.0.0 to 192.168.255.255

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3.1.2.7.1.2.5 PUBLIC IPV4 ADDRESSES
Are allowed for use on the Internet. The ranges of the public IPv4 addresses are as follows:
a. Class A - 1.0.0.0 to 9.255.255.255
11.0.0.0 to 126.255.255.255
b. Class B - 128.0.0.0 to 172.15.255.255
172.32.0.0 to 191.255.255.255
c. Class C - 192.0.0.0 to 192.167.255.255
192.169.0.0 to 223.255.255.255
3.1.2.7.2 SUBNET MASK
Each host on a TCP/IP network is assigned a unique 32-bit logical address, called subnet mask, which is
divided into two main parts: network ID portion of the IP address and the host ID portion of the IP address.
It enables one to know the network portion and host portion of any IP address.
If no subnet mask information is associated with the IP, then the default is to determine the network portion
and the host portion of this IP address depending on its IP class as shown in Table 3 below.
The subnet mask determines the network portion and the host portion of an IP address by converting the
network portion to all ones and converting the host portion to all zeros.
Subnet mask 255.255.255.0 (decimal) or /24 => 11111111.11111111.11111111.00000000 (binary)
Network ID - 1 bit portion of subnet mask
Host ID - 0 bit portion of subnet mask
Table 3.3: Subnet Mask for Different Classes of Networks
Class of IP Format Default Subnet Mask
A Network. host. host. host 255.0.0.0

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B Network. network. host. host 255.255.0.0
C Network. network. network. host 255.255.255.0
The theoretical method to get the network IP, is to make a logical AND operation between the IP and its
subnet mask.
3.1.2.7.3 IP SUBNET ADDRESSING (SUBNETTING)
Subnetting is to get many network IPs (called subnets) from only one network IP. To create subnetworks,
bits are taken from the host portion of the IP address and reserved to define the subnet address. Subnetting
provides the network administrator with several benefits, including extra flexibility, more efficient use of
network addresses, and the capability to contain broadcast traffic (i.e. a broadcast will not cross a router).
Subnets are under local administration. As such, the outside world sees an organization as a single network
and has no detailed knowledge of the organization’s internal structure. Subnetting can be done in three basic
ways:
1) Based on the number of subnetworks you wish to obtain from a single block of IP address.
2) Based on the number of host computers or devices you want to be connected to that
sub-network.
3) By reverse engineering which is a scenario in which a subnet mask and an IP address block is
given and the number of subnetworks and number of hosts per each subnet are found.
Based on the power of 2s (binary), there are some equations that allow us to determine the required details,
and these are:
i. Number of subnets = 2x
subnets
ii. Number of hosts per subnet = 2y
- 2 hosts

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iii. Block size / Increment = value of last network ID in decimal
3.1.2 NETWORK CONFIGURATION
3.1.2.1 CISCO IOS, ROUTER AND SWITCH
The Cisco IOS (Internetworking Operating System) is a proprietary kernel that provides routing, switching,
internetworking and communications features on Cisco routers and switches, and it’s what allows the
configuration of the devices as well.
3.1.2.1.1 CONNECTION TO A CISCO DEVICE
I learnt that there are three various ways to connect to Cisco router for configuration purposes:
1. The Console port: Rollover cable (also known as Cisco console cable) is a type of cable that is most
commonly used to connect a computer terminal to a router's console port. PuTTY or other terminal
emulators are used to open a console session, and then configure the router or switch.
2. The Auxiliary port: This port is usually used when one needs to configure the router out-of-band,
meaning out of the network. A switch does not have this port.
3. Use of an In-band program: This is done through the use of a terminal emulation program such as
Telnet or its secure form called SSH (SecureShell).
3.1.2.1.2 CISCO DEVICES HARDWARE
There are many models of routers and switches with certain capabilities and features, but every model
contains a certain number of Ethernet and Serial ports. Some models allow increase in their number ports by
plugging some in them.
The LAN is always connected to the router through its Ethernet port, hence the port is known as the LAN
interface. While the WAN is connected through the Serial port and called the WAN interface.

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3.1.2.1.3 THE CLI COMMANDS
The CLI (Command Line Interface) is the software interface that the network administrator uses in order to
configure the Cisco device. The CLI has different modes which permit configuration of a certain set of
functions.
i. Setup mode: This is the initial configuration mode, which contains interactive config dialogue that
enables one to to configure the Cisco device.
ii. USER EXEC mode: This is used for and limited to basic monitoring commands.
iii. PRIVILEGED mode: Provides access to all other router and switch commands.
iv. Global configuration mode: Commands made in this mode affect the entire system.
v. Specific configuration mode: Used for commands that affect interfaces/processes only.
3.1.2.2 CISCO PACKET TRACER
Packet Tracer is an exciting network design, simulation and modelling tool that allows one to develop skill
set in networking, cybersecurity, and the Internet of Things (IoT). It allows one to model complex systems
without the need for dedicated equipment. It is used to practice CCNA-level network configurations and
troubleshooting skills via a PC or computer devices.
Most importantly, it helps students and instructors create their own virtual network worlds for exploration,
experimentation, and explanation of networking concepts and technologies.
During my training at NEC, I was able practice and simulate many network scenarios using this software.
3.1.2.3 NETWORKS SIMULATED
I learnt how to perform basic administrative configurations such as hostnames, banners, passwords (enable,
console, telnet, SSH), management IP, default gateway, saving running-config, VLANs and so on; using a
real Cisco Catalyst 2950G switch. Then, I performed various tasks using the Packet Tracer to simulate
network labs for my configurations.

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3.1.2.3.1 A SMALL OFFICE
I designed a real world scenario of a small office, and applied various concepts such as subnetting, VLANs,
trunks etc.
Fig 3.19: A simulated small office network
After the design, I used a troubleshooting tool called PING, to test connectivity among all the device to
ensure the specifications are met.

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Fig 3.20: The virtual window of the network ADMIN’s PC

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Fig 3.21: The virtual window of a Sales PC
As can be seen from the pictures above, only computers in the same department could communicate with
with each other, but not with other department’s. And only the ADMIN could telnet and configure any of the
switches.
3.1.3 NETWORK SECURITY
There are many security threats that can affect a network. One of the best practices in network security is to
try and stop security threats from the entry-point of a LAN network. This means that the switch can play an
important role in network security since it’s the entry-point of the network.

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3.1.3.1 PORT SECURITY
This method is usually used to prevent layer 2 threats such as: STP attacks, ARP attacks, MAC Spoofing,
(VLAN) Hopping, DHCP spoofing and so on.
Port security is a method of securing an interface by only allowing traffic from a specific set or number of
MAC Address. If traffic from an invalid MAC is detected, it will be blocked or dropped. This is a low level
form of security that can be used to prevent unwanted devices from being connected to the network.
One can configure the interface for one of these violation modes, based on the action to be taken if a
violation occurs:
a) Restrict: A port security violation restricts data, causes the SecurityViolation counter to increment, and
causes an SNMP Notification to be generated. The rate at which SNMP traps are generated can be
controlled by the snmp-server enable traps port-security trap-rate command. The default value ("0")
causes an SNMP trap to be generated for every security violation.
b) Shutdown: A port security violation causes the interface to shut down immediately. When a secure port
is in the error-disabled state, you can bring it out of this state by entering the err-disable recovery
cause secure-violation global configuration command or you can manually re-enable it by entering
the shutdown and no shut down interface configuration commands. This is the default mode.
3.1.3.2 NETWORK ACCESS CONTROL (FOR ENTERPRISE NETWORKS)
Access Control: In the context of network security, access control is the ability to limit and control the
access to host systems and applications via communications links.
Network Access Control: Network access control (NAC) is an umbrella term for managing access to a
network. It authenticates users logging into the network and determines what data they can access and
actions they can perform. NAC also examines the health of the endpoints.
3.1.3.2.1 ELEMENTS OF A NETWORK ACCESS CONTROL SYSTEM

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1) Access requestor (AR): The AR is the node that is attempting to access the network and may be
any device that is managed by the NAC system. Also referred to as supplicants, or simply clients.
2) Policy server: It determines what access should be granted. It often relies on backend systems,
including antivirus, patch management, or a user directory, to help determine the host’s condition.
3) Network access server (NAS): It functions as an access control point for users in remote locations
connecting to an enterprise’s internal network. Also called a media gateway or a remote access
server, it may rely on itself or a policy server to provide authentication services.
3.1.3.2.2 NETWORK ACCESS ENFORCEMENT METHODS
Enforcement methods are the actions that are applied to ARs to regulate access to the enterprise network.
The common NAC enforcement methods are:
a. AAA and IEEE 802.1X: IEEE 802.1X is a link layer protocol that enforces authorization before a port
is assigned an IP address. IEEE 802.1X makes use of the Extensible Authentication Protocol for the
authentication process.
b. VLANs: A VLAN is a logical subgroup within a LAN that is created via software rather than manually
moving cables in the wiring closet. In this approach, the enterprise network, consisting of an
interconnected set of LANs, is segmented logically into a number of virtual LANs. The NAC system
decides to which of the network’s VLANs it will direct an AR, based on whether the device needs
security remediation, Internet access only, or some level of network access to enterprise resources.
c. Firewalls: A firewall provides a form of NAC by allowing or denying network traffic between an
enterprise host and an external user.
d. DHCP management: DHCP is an Internet protocol that enables dynamic allocation of IP addresses to
hosts. A DHCP server intercepts DHCP requests and assigns IP addresses instead. Thus, NAC
enforcement occurs at the IP layer based on subnet and IP assignment. A DCHP server is easy to install
and configure, but is subject to various forms of IP spoofing, providing limited security.

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3.1.3.2.3 EXTENSIBLE AUTHENTICATION PROTOCOL (EAP)
EAP provides a set of protocol which 802.1X port access protocol use to encapsulate and pass the
authentication information between the supplicant and the authentication server.
Which EAP type to implement, or whether to implement 802.1X at all, depends on the level of security that
the organization needs, the administrative overhead, and features desired.
3.1.3.2.4 VPN
Instead of relying on Wi-Fi LAN for authentication and privacy (encryption), many enterprises implement a
VPN. This is done by placing the access points outside the corporate firewall and having the user tunnel in
via a VPN Gateway; just as if they were a remote user. The downsides of implementing a VPN solution are
cost, initial installation complexities, and ongoing administration overhead.
3.1.4 TROUBLESHOOTING SKILLS
One of the basic IP addressing troubleshooting techniques learnt consist of four steps which are as follows:
1) Open a DOS window and ping loopback address: If failed, then there is a TCP/IP stack failure.
2) Ping the IP address of the localhost from same DOS window: If this is successful, then your
NIC is functioning well.
3) Ping the default gateway (router): If ping works, then the NIC is connected into the network, and
communicate with it.
4) Ping the remote server: If it works, then there is an IP communication between localhost and the
remote server.
By applying the above techniques, one can figure out at what level an issue lies: whether internal or external
to the computer system.

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3.2.0 ELECTRICAL MOTOR CONTROL
3.2.1 ELECTRIC MOTOR
An electric motor is an electric machine that converts electrical energy into mechanical energy. In normal
motoring mode, most electric motors operate through the interaction between an electric motor's magnetic
field and winding currents to generate force within the motor. In certain applications, such as in the
transportation industry with traction motors, electric motors can operate in both motoring and generating or
braking modes to also produce electrical energy from mechanical energy.
3.2.1.1 MOTOR CONTROL
Motor control is the basic electrical process by which an electrical motor is controlled be it an AC or a DC
motor. The electric motor can be categorized into different methods either by its intake voltage, by its mode
of connections or by its mode of starter.
3.2.1.2 DC MOTORS
Irrespective of the different types of DC motors, however suffice it to say that they are all connected in the
same manner. From the output of the motor terminal would be two wires where the right magnitude (either
12V, 24V etc. depending on the size of the motor) of the DC supply voltage is connected to it (+ve and –ve
terminals).
When connecting DC motor pay attention to the polarity of the plug or lead. Make sure to connect the +ve
lead to the positive terminal of the supply and –ve lead to the terminal marked -ve. As interchanging the
polarity will cause the motor to run/turn in the wrong (undesired) direction.
3.2.2 AC SQUIRREL CAGE INDUCTION MOTOR
The induction motor is also called Asynchronous Motor. It is classified into single phase and 3 phase. The
induction motor mainly deals with alternating current of 220Volts at a frequency of 50Hz.
3.2.2.1 3 PHASE INDUCTION MOTOR TERMINALS

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In these motor, 3 phase voltages (red, yellow and blue phases) from the mains supply is applied
to the stator winding via the electrical terminal of the motor. Meanwhile the body/chassis of the motor must
be grounded/earthed. Owing to the mechanical construction of the rotor (squirrel cage type) winding. It
starts rotating in as much as the stator winding has been supplied by the right voltage that is stated on the
name plate of the motor.
So on the motor terminals from where the electrical power is fed to the stator, there are 6 terminals (which
are actually 3 pairs of coils) which are labeled as U1, V1, W1, on one side and U2, V2, W2 on the other side.
Two of these terminals are similar (because it is a single coil) and so they are labelled with the same
alphabet. Thus we would have;
 U1 and U2 is one coil, U1 is the start coil and U2 is the end coil
 V1 and V2 is one coil, V1 is the start coil and V2 is the end coil
 W1 and W2 is one coil, W1 is the start coil and W2 is the end coil
And the arrangement on the terminals of the motor is as show below:
Plate 3.17: 220V AC Electric Motor

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3.2.2.2 CONNECTION OF INDUCTOR MOTORS TO AC SUPLLY
An induction motor's windings can be connected to a 3-phase AC line in two different ways:
i. Wye in U.S, star in Europe, where the windings are connected from phases of the supply to the
neutral;
ii. Delta (sometimes mesh in Europe), where the windings are connected between phases of the supply.
3.2.2.2.1 DELTA CONNECTION
One of the connection modes of the 3 phase induction motor is the DELTA CONNECTION. Some electrical
motors could be connected in delta form. When electrical motor is connected in delta at the terminal a small
metal is used to shunt the terminals in a vertical arrangement. It is such that the metal would shunt U1 and
V2, V1 and W2, W1 and U2 respectively. The picture below is a motor connected in delta
Plate 3.18: Delta connection mode
When the electrical motor is connected in delta the normal voltage from the line (i.e. from the supply) is
been supplied to the motor i.e. if your normal supply voltage per any pair phase (red/yellow, yellow/blue,
red/blue) is 415Volts; then this would be the voltage that would be on the motor’s terminal (i.e. in between
two different windings) when the supply is switched on.

50
After shunting the terminals vertically as shown in the figure above you can now connect your power supply
cable to any side of the coils either on U1, V1, W1 or V2, U2, W2.
3.2.2.2.2 STAR CONNECTION
One of the connection modes of the 3 phase induction motor is the STAR CONNECTION. In this mode, the
small metals are used to shunt the whole aspect of one section of the motor terminal and the power supply
cable must be connected only to the other side of the terminal and never to be shunted star joint side. We can
choose to shunt any aspect of the coil terminal (U1, V1, W1 or U2, V2, W2) and then put the supply cable
via the other side of the coil (but not on the same shunted side). The below is an image of star connection
mode.
Plate 3.19: Star connection mode
When the motor is connected in star mode, the shunted terminals forms the start point so that the voltage on
each windings is √(1/3) of the supply voltage unlike in the delta connection mode. Or for instance, if the
mains supply voltage is 15Volts then the voltage that appears on any pair of the coils must be 240Volts that
is 425(√1/3).
3.2.3 ELECTRICAL MOTOR STARTERS
Irrespective of connecting the electrical motor in star or delta mode, there will always be a switch or group
of switch gears that must be closed in other for current to flow from the mains power supply wired into the

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wires that is connecting the motor and then into the motor’s stator. And only to the large size of induction
motors (used industrially) and the large amount of in rush current that is taken in when the motor is started,
it is not a safe practice to use an ordinary air break switch to close the circuit for power supply to flow to the
motor; as well as in interrupting the power supply to the motor in other for it to come to a halt more so there
is equally the need to protect the motor from damages that could resort from problems like short circuit or
overload.
Thus, electrical motors are proper connected with the following component: circuit breakers (of fuses),
contractors, overload relays and start/stop push button switches. Sometimes these components could be
coupled together in a panel such that all one needs is to connect a power supply wires to the starter (on the
input side of the panel) and then from the output side of the panel the load wire will be connected. There is
also the advantage that the panel can be located remotely (far away) from the location where the motor is
installed. On the panel, there would be a button that can be pressed (start button) for the motor to start and
another button (stop button) to bring the motor to a halt. Such panels are regarded as motor starter panel or
motor drives. In industrial application, we would often come in contact with the following types of starters
and drives.
I. Direct Online Starters (DOL)
II. Star/Delta starters
III. Variable Frequency Drives (VFD)
I. Direct Online Starters (DOL) CONNECTION MODE OF ELECTRICAL MOTORS
This type of connection involves connection of the induction motor directly across the supply voltage (3
phase). With this type of connection in the event of starting of the motor, there is an in-rush of full current
that is required to give the motor maximum torque. The effect of this in-rush current is sometimes noticed
by the slight dimming of light (that are connected to the same power systems as the motor) in the event of
starting of the motor.
In order to carry out this connection to the motor several switch gears are placed in between the supply line
and the motor terminals to protect the motors from problems of short circuit, overload etc. Also, the

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connection can be done such that the motor can be started from distance very far from its point of
use/installation. So to carry out the wiring/building of a DOL starter, two types of circuit diagram is used to
describe it: the POWER CIRCUIT diagram and the CONTROL CIRCUIT diagram.
 POWER CIRCUIT DIAGRAM: This diagram shows how the main power gets to the motor from the
supply lines (mains). It tells the various switch gears that the power goes through. It is usually from
circuit breakers (or fuses) to contactors, overload relays and then to the terminals of the motor. The fig.
3.22 is a power circuit dig diagram of how the main power supply of either 220VAC or 415VAC gets to
the electric motor.
Fig 3.22: Power circuit diagram Fig 3.23: Control circuit diagram
 CONTROL CIRCUIT DIG: Even after connecting the electrical power from the mains up to the
electric motor terminal as described in the power circuit dig above and then close the circuit breaker, the
motor will not start as the contactor is not closed. So the electrical power will flow up to the supply part
of the contactor, but cannot go to the load part of the contactor until the contactor is closed. And the
contactor will not be closed until a (properly connected) START and STOP button is connected

53
properly with the auxiliary contacts of the contactor and the overload relay for proper operation of the
motor.
For the contactor to become closed the required voltage that is needed to energize the coils of the contactor
must be supplied to it. In the case of a contactor with single phase coil, then only a phase and neutral is
needed to be supplied to the contactor, however in a case of a contactor with a 2 phase coil, then two
different phases will be needed to energize the coil. The fig 3.23 is a control circuit of how the coils of the
contactor are energize using the start and stop buttons.
II. Star/Delta starters CONNECTION MODE
This is a form of reduced voltage starting of induction motor. It is usually used to start induction motors that
are of very large size (say from 7.5kW motor and above). If induction motor as large as 10kW and above
were to be started normally in a delta mode this would draw very large current from the power system at
start up for some seconds (which could seriously distort it and affect other loads like lightings that are
connected from the same power supply with the motor) thus leading to over sizing of the circuit breakers,
contactors and overload relays that are used to connect the motor. Besides the huge torque that is associated
with the delta starting may not be desired for some applications. Also after some seconds when the current
reduced to that which is needed to continuously run the motor, the already oversized switched gears (that
was put in place to enable the motor to start) won’t be able to protect the motor in event of overloading of
the motor. Besides the windings of the motor would become weak quickly owing to the large current that
results at start-up of large motors with the normal line voltage (which is usually 415VAC or more). Note
that the larger the motor the larger the multiple of start-up current. On the other hand if we just decide to
connect the motor in star, it would be just good in starting the motor normally without much stress on the
power system of the motor’s winding but the full speed output of the motor will be lesser than the required
output from the motor owing to reduced voltage created by running the motor in star mood (i.e. √3).
So in other to achieve good starting and good running of such large induction motors, one way to do this is
by the use of star/delta starters. These starters enables us to start the motor in star connection mode and after

54
running the motor for some seconds (when the large startup current drawn by large induction motor must
have died down and the motor must have attained a fair speed), then the starter switches to delta connection
mode (with the aid of a timer) in order to make the motor run on full speed. The items needed for the
star/delta connection are;
a) Three contactors (2 of the contactors must have at least one pair of NO and NC auxiliary contacts
each while the third must have at least 2 pairs of NO auxiliary contacts and a pair of NC auxiliary
contacts. From the first two contactors we call one the main/lime contactor, and the other we call
the delta contactor while the third is the star contactor).
b) One timer
c) One overload relay
d) One START and one STOP push buttons switches
e) Control cables for connecting all the components
f) Control fuse/MCB
If we label the main/line contactor as 1, the delta contactor as 2 and the star contactor as 3 then the sequence
of operation of the contactor are as follows: The contactor 3 (I.e. the star contactor) closes first and forms a
star point on contactor 2 (delta contactor) which appears on one side of the motor terminal (either terminals
u1, v1 & w1 or u2, v2 & w2 depending on the terminal in which the cables from contactor 2 is connected to).
Immediately the star contactor closes, almost at the same time the line or main contactor closes. There by
achieving the essence of this (star/delta) starting mechanism (i.e. to ensure that the motor is started on a
reduced voltage and current-tar, before increasing the voltage in order for the motor to achieve full speed by
changing to delta connection mode). Thus the star and the line contactors become closed. But from visual
inspection it will seem as if both contactors closes simultaneously, this is because of the high speed of
electric current flow. The start line contactors remain closed for a certain time that will be determined by the
set point on the timer. After a set time is reached, the timer times out and the star contactor only becomes de
energized. And then the delta contactor will become energize immediately. However in the course of this

55
change (i.e. from star connection to delta), the motor’s speed will slow down slightly and then builds up to
full speed when both contactors (main & delta) are fully engaged. Under normal continuous operation, the
main and the delta contactor carries the supply current to the motor. Thus the load current is divided
between both contactors and the motor resumes running on full speed (owing to the full current and voltage
that exist at the motor’s terminals). The figure below is the power and the control circuit of the star/delta
starter connection mode. The figure xxiii, is the power circuit of the star-delta connection mode.
The figure xxiv, is a functional control circuit but not the correct circuit because in its mode of operation,
once the timer starts counting the timer remains ON and his can cause the timer to get faulty. While the
figure xxv, control circuit 2 is the correct control circuit of the star-delta connection mode, because once
the timer starts counting the timer goes OFF.
Fig:
Fig 3.24: Power circuit Fig3.25 : Control circuit 1

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Fig
3.26: Control circuit 2
III. Variable Frequency Drives (VFD)
It is an electronic controller used to change the speed of a normal electric induction motor. The variable
frequency drive is capable of controlling the electric motor via, several ports either by BOP, TOP or by a
remote connection. It can also be called a variable speed drive, or an inverter drive. A variable-frequency
drive (VFD) or adjustable-frequency drive (AFD), variable voltage/variable-frequency (VVVF) drive,
variable speed drive, AC drive, micro drive or inverter drive is a type of adjustable-speed drive used in
electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency
and voltage. VFDs are used in applications ranging from small appliances to large compressors. About 25%
of the world's electrical energy is consumed by electric motors in industrial applications, which can be more
efficient when using VFDs in centrifugal load service; however, the global market penetration for all
applications of VFDs is relatively small. Over the last four decades, power electronics technology has
reduced VFD cost and size and has improved performance through advances in semiconductor switching
devices, drive topologies, simulation and control techniques, andcontrol hardware and software. VFDs are
made in a number of different low- and medium-voltage AC-AC and DC-AC topologies.

57
3.2.4 BRANDS OF VARIABLE FREQUENCY DRIVES (VFD)
There are several companies that are responsible for the manufacturing and production of the VFDs. Some
of this companies includes ABB ltd, American Electric Technologies Inc. (Aeti), Crompton Greaves Ltd,
Danfoss Vlt Drives, Eaton Corp, Emerson Industries Automation, Fuji Electric Co. Ltd, Ge Energy Power
Conversion, Hiconics Drive Technology Co. Ltd, Hitachi Ltd, Johnson Controls Inc., Honeywell
international Inc., Kb Electronic Inc., Mitsubishi Electric corporation, Rockwell Automation Inc, Schneider
Electric Sa, Siemens Industry Inc., Toshiba international corporation, Vacon Plc, Yaskawa Electric Corp,
and so on.
VFD manufacturers mainly focus on R&D in order to develop new and improved products, which offer
more distinguished and revolutionary features such as more precision, control, and efficiency. Expansion
into new and emerging markets such as Asia-Pacific, Russia, and South America has been and will be the
key for success for VFD manufacturers if they intend to increase their overall sales and revenue. . In 2012,
ABB Ltd (Switzerland) dominated the VFD market with 19% market share. Siemens Industry Inc. (U.S.)
stood second with 13.8% and Schneider Electric SA (France) occupied around 8.5% market share of the
total VFD market share.
Plate 3.20: Schneider Inverter drive Plate 3.21: Siemens Inverter drive

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3.2.4.1 SYSTEM DESCRIPTION AND OPERATION
A variable-frequency drive is a device used in a drive system consisting of the following three main
sub-systems: AC motor, main drive controller assembly, and drive/operator interface
3.2.5 FORWARD AND REVERSE
In this connection mode, the main motor itself can be connected in star or delta mode and the right voltage
be made available according to the specification on the name plate of the motor. But in order to connect the
motor so that when we press one button it turns clockwise direction and after it is stopped, on pressing
another button the motor will turn in counter clockwise direction, it is termed the reverse connection mode.
3.2.5.1 POWER AND CONTROL CIRCUIT OF THE FORWARD AND REVERSE INDUCTION
MOTOR
Fig 3.27:Forward/Reverse Induction motor

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3.2.6 VARIABLE FREQUENCY STARTER (VFD)
Variable-frequency drives (VFD) can be of considerable use in starting as well as running motors. A VFD
can easily start a motor at a lower frequency than the AC line, as well as a lower voltage, so that the motor
starts with full rated torque and with no inrush of current. The rotor circuit's impedance increases with slip
frequency, which is equal to supply frequency for a stationary rotor, so running at a lower frequency actually
increases torque.
3.2.6.1 PROGRAMMING A VFD
Depending on the model a VFD's operating parameters can be programmed via: dedicated programming
software, internal keypad, external keypad, or SD card. VFDs will often block out most programming
changes while running. Typical parameters that need to be set include: motor nameplate information, speed
reference source, and braking control. It is also common for VFDs to provide debugging information such as
fault codes and the states of the input signals.
3.2.6.1.1 DRIVE OPERATION
Referring to the accompanying chart, drive applications can be categorized as single-quadrant, two-quadrant,
or four-quadrant; the chart's four quadrants are defined as follows:
1) Quadrant I - Driving or motoring, forward accelerating quadrant with positive speed and torque.
2) Quadrant II - Generating or braking, forward braking-decelerating quadrant with positive speed and
negative torque.
3) Quadrant III - Driving or motoring, reverse accelerating quadrant with negative speed and torque.
4) Quadrant IV - Generating or braking, reverse braking-decelerating quadrant with negative speed
and positive torque.
Most applications involve single-quadrant loads operating in quadrant I, such as in variabletorque (e.g.
centrifugal pumps or fans) and certain constant-torque (e.g. extruders) loads.

60
Certain applications involve two-quadrant loads operating in quadrant I and II where the speed is positive
but the torque changes polarity as in case of a fan decelerating faster than natural mechanical losses. Some
sources define two-quadrant drives as loads operating in quadrants I and III where the speed and torque is
same (positive or negative) polarity in both directions.
Certain high-performance applications involve four-quadrant loads (Quadrants I to IV) where the speed and
torque can be in any direction such as in hoists, elevators, and hilly conveyors. Regeneration can occur only
in the drive's DC link bus when inverter voltage is smaller in magnitude than the motor back-EMF and
inverter voltage and back-EMF are the same polarity.
In starting a motor, a VFD initially applies a low frequency and voltage, thus avoiding high in rush of
current associated with direct-on-line starting. After the start of the VFD, the applied frequency and voltage
are increased at a controlled rate or ramped up to accelerate the load. This starting method typically allows a
motor to develop 150% of its rated torque while the VFD is drawing less than 50% of its rated current from
the mains in the low-speed range. A VFD can be adjusted to produce a steady 150% starting torque from
standstill right up to full speed. However, motor cooling deteriorates and can result in overheating as speed
decreases such that prolonged lowspeed operation with significant torque is not usually possible without
separately motorized fan ventilation. With a VFD, the stopping sequence is just the opposite as the starting
sequence. The frequency and voltage applied to the motor are ramped down at a controlled rate. When the
frequency approaches zero, the motor is shut off. A small amount of braking torque is available to help
decelerate the load a little faster than it would stop if the motor were simply switched off and allowed to
coast. Additional braking torque can be obtained by adding a braking circuit (resistor controlled by a
transistor) to dissipate the braking energy. With a four-quadrant rectifier (active front-end), the VFD is able
to brake the load by applying a reverse torque and injecting the energy back to the AC line.
3.2.6.2 ELECTRICAL WIRING OF THE VARIABLE FREQUENCY DRIVE (VFD)
The variable frequency drive is electrically wired to an output motor, such as; a conveyor, an electric motor,
a pulley motor system, a moving crane, an electric train, blowers, fans, compressor, stirrers, pressers,
vacuum pumps, crushers and so on. The electrical circuit is as follows;

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Figure 3.28: Wiring of a variable frequency drive (VFD)
3.2.7 EKTS SOFTWARE
The EKTS software is a simulator for learning Electromechanical Control Systems (ECS). It helps students
to easily design and test a solution circuit for a given problem and it has a flexible structure and
user-friendly interface.
3.2.7.1 The EKTS and It’s Operational Procedure
The simulator, EKTS, is developed in the environment of Microsoft C#.NET and is basically divided into
three main sections:
1) Work Sheet: The electrical control and power circuits are designed in the Work Sheet by means of
ladder diagram programming format.
2) Tool Bar: The icons of basic operations of files for opening, saving, running, printing, etc. are located
in the Tool Bar.
3) Library: All the components, the systems, the power sources and the motors are within the Library.
The simulator has been designed to reinforce the training and enable participants of the course to quickly
design and test new circuit before physical realization of the application. It will also increase self-confidence
of the students and strengthen the interest to the course will consciously and willingly participate in
laboratory and industrial studies. The start up window, the work environment and library window of the
ECSS is shown in the figure below.

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Fig. 3.29: The start up window, the work environment window of the EKTS
All of the components are in the library section. This section has four main parts as seen on Fig. 3.
i. AC Power supplies: There are single and three phase ac supplies in the AC Power supplies menu.
ii. Components: Contactor, time-relays, switches, buttons, open and closed contacts etc. are located in the
Components menu.
iii. Induction motors: Single and three phase squirrel cage induction motors are under the Induction
motors menu.
iv. Systems: A five-floor elevator and two kind of gate systems are in the Systems menu.
Fig. 3.30 The library section of the ECSS
The ECSS has also an help menu. Users can easily learn all information about the simulator such as how to
design a circuit on the simulator or how to use it and etc.

63
Fig 3.31: The Help window
3.2.7.2 WORKDONE
Some of the circuits drawn and simulated using the EKTS include: Star-Delta motor starter, ATS
(Automatic Transfer Switch), Forward and Reverse, Direct Online starter, Gate system, and so on.
A. Star-Delta
Fig 3.32: Star-delta circuit in EKTS
B. ATS
Fig 3.33: ATS circuit in EKTS

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3.2.7.3 BENEFITS OF USING EKTS
a. If there are some mistakes or wrong connections it can be seen easily and corrected.
b. It can be used to design far more complicated control circuit such as
c. Students can understand and test it easily and in a very short time by using ECSS.
d. In practice, this kind of circuits mostly includes high voltage, and due to carelessness electrical
shock can occur. But by using EKTS, there is no risk for electrical shock or other dangerous
situations.
e. Performing modifications on designed circuit is easy and takes a few second in EKTS.
3.2.8 PRACTICAL CLASSES
3.2.8.1 ON ELECTRICAL AND MOTOR CONTROL STARTERS
Plate 3.22: Star-delta motor starter system

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Plate 3.23: ATS (Automatic Transfer Switch)
3.2.8.2 PHASE FAILURE/SEQUENCE DEVICE
Phase sequence relay is an electronic changeover type relay, which provide normally open or normally
closed type output, when the correct phase sequence of a three phase system is interrupted. They are widely
used in three phase power monitoring applications and for protection, where we have to monitor and control
the raw power supplied from the source.
3.2.8.2.1 IMPORTANCE OF THE DEVICE
Major industrial loads such as three phase induction or synchronous motors are connected in positive phase
sequence with the supply. However, if the phase sequence is suddenly reversed from the supply side, that is
“BYR” instead of “RYB”, then the motor will start rotating in reverse direction, which might cause damage
to the device and its immediate environment.
3.2.8.2.2 PHASE FAILURE DEVICE CONNECTION
In a phase sequence relay, there are three major segments. The input side, the internal circuit and the NO/NC
output. The three phase mains is connected in the input side of the relay. The internal circuit of the phase

66
sequence relay contains a voltage comparator, which continuously detects and monitor the positive phase
sequence.
And finally the output side provides potential free NO/ NC changeover. Typically, the output relay contact is
capable to carry a maximum of 1100 VA load, and beyond that you must connect a higher current rated
contactor in between the phase sequence relay and load.
Fig 3.34: Basic circuit for Plate 3.24: Wiring of a phase Plate 3.25: Completed
phase
Phase failure device failure system failure system

67
3.3.0 INDUSTRIAL AUTOMATION
3.3.1 INTRODUCTION
The word Automation gives the meaning self dictating or a mechanism move by itself that derived from the
Greek words Auto and Matos where auto means self while matos means moving. Automation goes a step
further than mechanization that uses a particular machinery mechanism aided by human operators for
performing a task.
Mechanization is the manual operation of a task using powered machinery that depends on human decision
making. On the other hand, automation replaces the human involvement with the use of logical
programming commands and powerful machineries.
Hence, Industrial Automation, can be defined as the use of set of technologies and automatic control devices
that results in the automatic operation and control of industrial processes without significant human
intervention and achieving superior performance than manual control. These automation devices include
PLCs, PCs, PACs, etc. and the technologies include various industrial communication systems.
Figure 3.35: An automation system
3.3.2 PROGRAMMABLE LOGIC CONTROLLERS (PLCs)
The PLC can be explained to be a device that is used in an automation industry to replace most or all human
effort. A programmable logic controller (PLC), or programmable controller is an industrial digital computer
which has been made rugged and adapted for the control of manufacturing processes, such as assembly,
lines or robotics devices, or any activity that requires high reliability control and ease of programming and
process fault diagnosis.
They were first developed in the automobile industry to provide flexible, rugged and easily programmable
controllers to replace hard-wired relays, timers and sequencers. Since then they have been widely adopted as

Aroso Emmanuel A. - IT Technical Report.pdf

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