Level I - dl.otvet.gov.et

Ethiopian TVET-System

Electro Mechanical Equipment Operation and Maintenance

Level –I Based on March, 2017G.C. Occupational Standard

TTLM Code: EIS EMW1 TTLM 0919v1

Module Title: Applying Basic Electrical Electronics

Principle

TTLM Code: EIS EMW1 TTLM 0920v1

September, 2020

Electro-Mechanical Equipment Operation

and Maintenance

Level-I

Author/Copyright: Federal TVET

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This module includes the following Learning Guides

LG 47: Plan and prepar to identify

electrical/electronicparts

LG CODE: EIS EMW M12 LO1 LG-47

LG 48: Identify and test Electrical/electronic parts

LG Code: EIS EMW M12 LO2 LG-48

LG 49: Test the construction of electrical/ electronic

circuits

LG Code: EIS EMW M12 LO3 LG-49


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Instruction Sheet Learning Guide 47: Plan and prepar to identify

electrical/electronicparts

This learning guide is developed to provide you the necessary information regarding the

following content coverage and topics –

Following prepare to ensure OHS policies and procedures

Preparing short circuit, open circuits, grounding and close circuits

Preparing Coil, capacitor and resistor

Preparing contractors, relays, transformers, fuses and breakers

Checking Electrical system’ components

Determining location in which specific items of accessories, apparatus and circuits

are to be installed

Obtaining tools and testing devices needed to carry out the electrical circuits

This guide will also assist you to attain the learning outcome stated in the cover page.

Specifically, upon completion of this Learning Guide, you will be able to –

Follow prepare to ensure OHS policies and procedures

Prepare short circuit, open circuits, grounding and close circuits

Prepare Coil, capacitor and resistor

Prepare contractors, relays, transformers, fuses and breakers

Check Electrical system’ components

Determine location in which specific items of accessories, apparatus and circuits

are to be installed

Obtain tools and testing devices needed to carry out the electrical circuits

Learning Instructions:

1. Read the specific objectives of this Learning Guide.

2. Follow the instructions described in number 3 to 15.

3. Read the information written in the “Information Sheets 1”. Try to understand what are

being discussed. Ask you teacher for assistance if you have hard time understanding them.

4. Accomplish the “Self-check 1” in page .

5. Ask from your teacher the key to correction (key answers) or you can request your teacher

to correct your work. (You are to get the key answer only after you finished answering the

Self-check 1).

6. If you earned a satisfactory evaluation proceed to “Information Sheet 2”. However, if your

rating is unsatisfactory, see your teacher for further instructions or go back to Learning

Activity #1.

7. Submit your accomplished Self-check. This will form part of your training portfolio.


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8. Read the information written in the “Information Sheet 2”. Try to understand what are being

discussed. Ask you teacher for assistance if you have hard time understanding them.

9. Accomplish the “Self-check 2”



Self-check 2).

11. Read the information written in the “Information Sheets 3 . Try to understand what are






15. Do the “LAP test” in page __ (if you are ready). Request your teacher to evaluate your

performance and outputs. Your teacher will give you feedback and the evaluation will be

either satisfactory or unsatisfactory. If unsatisfactory, your teacher shall advice you on

additional work. But if satisfactory you can proceed to Learning Guide #18.


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Information Sheet-1 OHS policies and procedures

Introduction

Occupational safety and health (OSH) is generally defined as the science of the anticipation,

recognition, evaluation and control of hazards arising in or from the workplace that could impair

the health and well-being of workers, taking into account the possible impact on the

surrounding communities and the general environment. This domain is necessarily vast,

encompassing a large number of disciplines and numerous workplace and environmental

hazards. A wide range of structures, skills, knowledge and analytical capacities are needed to

coordinate and implement all of the “ electrical-electronics work activities /machine installation”

that make up national OSH systems so that protection is extended to both workers and the

environment. 1.2 OHS guidelines

Occupational safety and health is an extensive multidisciplinary field, invariably touching on

issues related to scientific areas such as medicine – including physiology and toxicology –

ergonomics, physics and chemistry, as well as technology, economics, law and other areas

specific to various industries and activities. Despite this variety of concerns and interests,

certain basic principles can be identified, including the following:

All workers have rights: - Workers, as well as employers and governments, must ensure

that these rights are protected and must strive to establish and maintain decent working

conditions and a decent working environment. More specifically:

work should take place in a safe and healthy working environment;

conditions of work should be consistent with workers’ well-being and human dignity;

work should offer real possibilities for personal achievement, self-fulfillment and

service to society.

OHS policies must be established: - Such policies must be implemented at both the

national (governmental) and enterprise levels. They must be effectively communicated to

all parties concerned.

Occupational safety and health programs and policies must aim at both prevention

and protection: - Efforts must be focused above all on primary prevention at the workplace

level. Workplaces and working environments should be planned and designed to be safe

and healthy.

Continuous improvement of occupational safety and health must be promoted:- This

is necessary to ensure that national laws, regulations and technical standards to prevent


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occupational injuries, diseases and deaths are adapted periodically to social, technical and

scientific progress and other changes in the world of work.

Health promotion is a central element of occupational health practice:-Efforts

Occupational health services covering all workers should be established. Ideally, all

workers in all categories of economic activity should have access to such services, which

aim to protect and promote workers’ health and improve working conditions.

Education and training are vital components of safe, healthy working environments

Workers and employers must be made aware of the importance of establishing safe

working procedures and of how to do so. Trainers must be trained in areas of special

relevance to particular industries, so that they can address the specific occupational safety

and health concerns.

Workers, employers and competent authorities have certain responsibilities, duties

and obligations:- For example, workers must follow established safety procedures;

employers must provide safe workplaces and ensure access to first aid; and the competent

authorities must devise, communicate and periodically review and update occupational

safety and health policies.

1.3. Occupational safety, health and working environment

Article 92 clearly spells out the fundamental

obligations of an employer with regard to putting in

place of all the necessary measures in order to

ensure, work places are safe, healthy and free of

any danger to the well being of workers.

Article 93. In this article the law provides the

obligations of workers pertaining to the required co-

operation and putting in to practice of the regulation

and instruction given by the employer in order to

ensure safety health and working conditions at work

places.

All electrical work should be carried out by a

qualified electrician. Under OSH laws, regular

inspection according to Ethiopian building code of

standard (EBCS)

Fig 1.1 OSH personal protective equipment


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Fig 1.2 OSH warning sign


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Self-Check 1 Written Test

Name: _________________________ Date: _______________

Directions: Answer all the questions listed below. Illustrations may be necessary to aid some

explanations/answers.

1. What is OSH (2 point)

2. What is the importance of OHS safety polices and procedure? (2 point)

3. what are the basic principles of OHS? write some of it. (2 point)

4. Write the personal protective equipment of electrical work. (2 point)

Note: Satisfactory rating –3 points Unsatisfactory - below 3 points

Answer Sheet

Name: _________________________ Date: _______________

Short Answer Questions

1. ________________________________________________________________

________________________________________________________________

2. ________________________________________________________________

________________________________________________________________

3. ________________________________________________________________

________________________________________________________________

4. ________________________________________________________________

________________________________________________________________

Score = ___________

Rating: ____________


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Information Sheet-2 Electric Circuit

Introduction

Fundamental of electricity

Electricity:- is the flow of free electrons in a conductor from one atom to the next atom in the

same general direction

Electrical quantities and measurement

All matter is composed of molecules which are made up of a combination of atoms. Atoms

have a nucleus with electrons orbiting around it. The nucleus is composed of protons and

neutrons (not shown). Most atoms have an equal number of electrons and protons. Electrons

have a negative charge (-). Protons have a positive charge (+). Neutrons are neutral. The

negative charge of the electrons is balanced by the positive charge of the protons. Electrons

are bound in their orbit by the attraction of the protons. These are referred to as bound

electrons.

Fig 2.1 the relation b/n electron, proton and nucles

Electric Charges

Electrons in the outer band of an atom are easily displaced by the application of some external

force. Electrons which are forced out of their orbits can result in a lack of electrons where they

leave and an excess of electrons where they come to rest. The lack of electrons is called a

positive charge because there are more protons than electrons. The excess of electrons has

a negative charge. A positive or negative charge is caused by an absence or excess of

electrons. The number of protons remains constant.


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Fig 2.3 electric charging relation

When two like-charged bodies are brought together, their electric fields repel one body from

the other. When two unlike-charged bodies are brought together, their electric fields attract one

body to the other. The electric field around a charged body forms invisible lines of force. These

invisible lines of force cause the attraction or repulsion.

Lines of force are shown leaving a body with a positive charge and entering a body with a

negative charge.

Fig 2.4 like and unlike charge

2.1. Types of Electrical Circuit

Introduction

Circuits :-is a complete path for current when voltage is applied .all circuits requires the

following components

1. Electrical Sources (for delivering electricity to the circuit and these are mainly electric

generators and batteries)

2. Controlling Devices (for controlling electricity and these are mainly switches, circuit

breakersetc.)

3. Protection Devices (for protecting the circuit from abnormal conditions and these are

mainly electric fuses ).

4. Conducting Path (to carry current one point to other in the circuit and these are mainly

wires or conductors)

http://www.electrical4u.com/electrical-fuse-hrc-fuse-high-rupturing-capacity/


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5. Load :is the electrical energy converted from one form to another form or the energy

consumed device

I. Current

Current is flow of electrons through the conductors .

It is designated by the symbol “I”.

Current is determined by the number of electrons that pass through a cross-section of a

conductor in one second. It is measured in amperes which is abbreviated “amps”. The letter

“A” is the symbol for amps.

A current of one amp means that in one second about 6.24 x 1018 electrons move through a

cross-section of conductor.

An electric current is produced when free electrons move from one atom to the next.

According to their conductivities materials are classified in three catagories

1. conductors.

2. insulators.

3. Semiconductor

conductors.:-Materials that permit many electrons to move freely are called conductors.

Such as Copper, silver, aluminum, zinc, brass, and iron.

insulators. are a materials that cannot allow free electrons through it are called insulators.

such as plastic, rubber, glass, mica, and ceramic are good insulators..

Fig 2.5 insulator and conductor

Semiconductor materials,such as silicon, can be used to manufacture devices that have

characteristics of both conductors and insulators. Many semiconductor devices will act like a

conductor when an external force is applied in one direction. When the external force is

applied in the opposite direction, the semiconductor device will act like an insulator. This

principle is the basis for transistors, diodes, and other solid-state electronic devices.

Prefix Symbol Decimal

1kiloampere 1 kA 1000 A

1milliampere 1 mA 1/1000 A

1microampere 1 mA 1/1,000,000 A

II. Voltage


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Voltage: is electrical pressure that pushes electric current through the conductors.

It is designated by the letter “E”, or the letter “V”. The unit of measurement for voltage is volt

which is also designated by the letter “V”.

Electricity can be compared with water flowing through a pipe. A force is required to get water

to flow through a pipe. This force comes from either a water pump or gravity.

Fig 2.6 current flow

An electrical voltage can be generated in various ways.

- From battery (electrochemical process)

- From power plant generator

AC/Dc source

Fig 2.7 voltage difference

The terminals of a battery are indicated symbolically on an electrical drawing by two lines. The

longer line indicates the positive terminal. The shorter line indicates the negative terminal.


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Fig 2.8 symbol of battery

The following chart reflects special prefixes that are used when dealing with very small or large

values of voltage:


1kilovolt 1 kV 1000 V

1millivolt 1 mV 1/1000 V

1microvolt 1 mV 1/1,000,000 V

III. Resistance

Resistance is the opposition of the flow of electrical current through the conductors. The

amount of resistance depends upon composition, length, cross-section and temperature of the

resistive material. As a rule of thumb, resistance of a conductor increases with an increase of

length or a decrease of cross-section. Resistance is designated by the symbol “R”. The unit of

measurement for resistance is ohms

Fig 2.9 Symbol of resistance

The following chart reflects special prefixes that are commonly used when dealing with values

of resistance:


1kilohm 1 kΩ 1000 Ω

1megohm 1 MΩ 1,000,000 Ω

I. Ohm’s Law

Ohms law states that current is directly proportional to voltage and inversely proportional to

resistance :

Mathematically I∝V/R

Where I= current in amper (A) and measured by ammeter and

V = voltage in volt (V) and measured by voltmeter

R=resistance in ohm (Ω) and measured by ohmmeter


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There is an easy way to remember which formula to use. By arranging current, voltage and

resistance in a triangle, one can quickly determine the correct formula.

Where I= Current

E=Voltage

R= Resistance

II. Power

Power is the rate of doing work/ the product of voltage and current i.e. in an electrical circuit,

voltage applied to a conductor will cause electrons to flow and is represented by the symbol

“P”.

It is measured in watts, represented by the symbol “W”. In a direct current circuit, one watt is

the rate work is done in a circuit when 1 amp flows with 1 volt applied.

In a DC circuit, power is the product of voltage times current. Later in this course, you will learn

a slightly different version of this relationship for an alternating current (AC) circuit.

Two other power equations can be derived from this formula by substituting other components

of Ohm’s Law.

Whether we measure power in the unit of "horsepower" or the unit of "watt," we're still talking

about the same thing: how much work can be done in a given amount of time. The two units

are not numerically equal, but they express the same kind of thing. In fact, European

automobile manufacturers typically advertise their engine power in terms of

kilowatts (kW), or thousands of watts, instead of horsepower! These two units of power are

related to each other by a simple conversion formula:

2.1.1 Structural Categories of Electriccircuits

1. Series Circuit


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2. Parallel Circuit

3. Series Parallel Circuit.

1. Series Circuit

Series circuit is a circuit in which components are connected end to end or

elements /components / are connected one after another in tail to head fashion.

Fig 2.10a series circuit

RULES FOR SERIES CIRCUITS

The value of a current flowing in a series circuit is the same through all parts of the

circuit.

That means; IT=I1=I2=……. =In Where IT= the total current path in the circuit

I1, I2…In is the current path in individual components

The total voltage of a series circuit is equal to the sum of the voltages across each part

of the circuit.

Mathematically VT=V1+v2+v3……………+Vn Where VT= the source voltage

V1, V2, V3……,Vn is the voltage drop across individual components


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The total resistance of a series circuit is equal to the sum of the resistances across each

part of the circuit.

RT=R1+R2+……………………..+Rn

Where RT the total resistance of the circuits

R1, R2…., Rn the individual resistance connected in the circuits

Fig 2.10b series circuit

2. Parallel Circuit

In parallel circuits

Parallel circuit: is a circuit in which components are connected side by side.

The total current supplied to parallel circuit is equals to the sum of the current through

the brunch circuit

The voltage across any branch of a parallel circuits is equal to the supply voltage

The total resistance in parallel circuit is the sum of the reciprocal the resistance

connected in the circuits


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Fig 2.11 parallel circuit

3. Series/Parallel or Combination Circuits

Certain circumstances require the use of Series/Parallel, or Combination, circuits, in which

series and parallel circuits are combined. Application area is used in industries and in different

electronics components.

Fig 2.12 combination circuit

According to cause and effect there four types of circuits

1. Short Circuit

A short circuit is simply a low resistance connection between the two conductors supplying

electrical power to any circuit.


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Short circuit can be

Unwanted path between part of circuit and ground

Unwanted path between two part of a circuit

Unwanted path between two separate circuits

Unwanted current path inside a component

Short circuit may cause excessive current this typically below the circuits fuse or breaker and it

is impossible to troubleshoot the circuit under power. .

2. Open Circuit

If due to disconnection of any part of an electric circuit if there is no flow of

current the circuit is said to be open circuited.


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Figure 2.13..Testingopen circuit with multimeter

3. Closed Circuit

If there is no discontinuity in the circuit and current can flow from one part to another part of the

circuit then the circuit is said to be closed circuit.

Figure example of simple closed circuit

Fig 2.13 simple closed electric circuit

4. Grounding In an electrical circuit, there is what’s known as an active wire, which supplies the power, and a

neutral wire, which carries that current back. An additional ‘grounding wire’ can be attached to

outlets and other electrical devices and also securely connected to the ground at the breaker


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box. This ground wire is an additional path for electrical current to return safely to the ground

without danger to anyone in the event of a short circuit. If a short circuit did occur, the current

would flow through the ground wire, causing a blown fuse or tripped circuit breaker

The importance of grounding electricity

protect against electrical overloadsystem.

Helps direct electricity: - helps allowing electrical currents to safely and efficiently travel

throughout your electrical system.

Stabilizes voltage levels: to ensure circuits aren’t overloaded and blown.

Easily discharges through the earth

Prevents damage, injury and death


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Directions: Answer all the questions listed below. Use the Answer sheet provided in the next

page:

1. What is circuit ? (3 point)

2. Write the different types of circuit? (3 point)

3. What are the structural features of electric circuit? (3 point)

4. Draw the circuit diagram of series and parallel circuit. (5 point)

5. Write importance of grounding. (3 point)

Answer Sheet

Name: ______________ Date: _______________


1. ________________________________________________________________

________________________________________________________________

2. ________________________________________________________________

________________________________________________________________

3. ________________________________________________________________

________________________________________________________________

4. ________________________________________________________________

________________________________________________________________

5. ________________________________________________________________

Note: Satisfactory rating –10 points Unsatisfactory - below 10 points You can ask you teacher for the copy of the correct answers.

Score = ___________

Rating: ____________


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Information Sheet-3 Basic Electrical/electronic devices

(component)

INTRODUCTION

An electronic circuit is composed of various types of components. Some of these components

are termed as active components because they take part in the transformation of the energy

while other components, which only dissipate or store energy, are called as passive elements.

Rectifier, transistors are some of-the common active while the resistances, which dissipate the

power and energy storing elements such as capacitances and inductances are known as

passive elements. The transformers may be regarded as a matching device

Difference between Electrical and Electronics Devices

Key difference: Electrical is defined as anything relating to or concerned with electricity.

Electronics is defined as the science and technology concerned with the development and

applications of electronic devices and circuits

Electrical Electronics

Definition

Electrical is defined as

anything relating to or

concerned with electricity.

Electronics is defined as the science and

technology concerned with the development and

applications of electronic devices and circuits.

Behavior

Electrical devices mainly

change current into another

form of energy such as heat

or light.

Electronics devices manipulate current in such a

way so that it can do a particular task.

Relation It relates to producing or

being operated by electricity.

It is concerned with application of devices

involving flow of electrons.


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Manipulation Electrical devices do not

manipulate data.

Electronic devices can manipulate data to assign

meaning to it.

Current flow They use Alternate Current

i.e. AC They use Direct Current i.e. DC

Voltage They use high voltage. They work on low voltage.

Table 3.1 the different between electrical electronics

Example of electrical devices are

Washing machine, Socket, fuse and motor, Heavy transformers

Example of electronic device:

Small transformer, small electronic components like resistor, diodes, inductors capacitors etc.

2.1 Types of Electric Circuit components

Electrical circuit components or devices are dividing in to two basic types

1. Passive component

2. Active component

1. Passive component

The element which receives energy (or absorbs energy) and either converts it into heat or

stored it in an electric or magnetic field called Passive Element. In other word; Those devices

or components which do not required external source to

theiroperationiscalledPassiveComponents.

Example: Resistor, Inductor, Capacitor, Transformer etc.

1.1. Inductor

An inductor is a passive electronic component which is capable of storing electrical energy in the form of magnetic

energy.

Fig 3.1 wound coil

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Inductance :-is the property of an electric circuit that opposes any change in electric current.

Resistance opposes current flow; inductance opposes change in current flow. Inductance is

designated by the letter “L”. . The unit of measurement for inductance is the Henry (h).

The inductance of a coil is determined by the number of turns in the coil, the spacing between

the turns, the coil diameter, the core material, the number of layers of windings, the type of

winding, and the shape of the coil. Examples of inductors are transformers, and motors.

Inductance circuit symbols

Fig 3.2 symbol of inductor

Fig 3.3 different types of inductors

1.2. Capacitor

Capacitor:- is an electrical component that stores energy in the electric filed .

A capacitor is made up of a pair of conductive plates separated by a thin layer of insulating

material. Another name for the insulating material is dielectric material. When a voltage is

applied to the plates, electrons are forced onto one plate. That plate has an excess of

electrons while the other plate has a deficiency of electrons. The plate with an excess of

electrons is negatively charged. The plate with a deficiency of electrons is positively charged.


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Fig 3.4 Typical capasitor

Direct current cannot flow through the dielectric material because it is an insulator; however it

can be used to charge a capacitor. Capacitors have a capacity to hold a specific quantity of

electrons. The capacitance of a capacitor depends on the area of the plates, the distance

between the plates, and the material of the dielectric. The unit of measurement for capacitance

is farads (F). Capacitors usually are rated in μF (microfarads), or pF (picofarads).

1.3. Resistor

It is a passive two-terminal electrical component that implements electrical resistance as a

circuit element .

Types of Resistor

Resistors can be divided in construction type as well as resistance material. The following

breakdown for the type can be made:

Fixed resistors

Variable resistors, such as the:

1. Potentiometer

2. Rheostat

3. Trim pot

http://www.resistorguide.com/fixed-resistor/

http://www.resistorguide.com/variable-resistor/

http://www.resistorguide.com/potentiometer/

http://www.resistorguide.com/rheostat/

http://www.resistorguide.com/trimpot/


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1.4. Transformer

Electrical power transformer is a static device which transforms electrical energy from one

circuit to another without any direct electrical connection and with the help of mutual induction

between two windings.

It transforms power from one circuit to another without changing its frequency but may be in

different voltage level.

Principle of operation transformer Whenever we apply alternating current to an electric coil, there will be an alternating flux

surrounding that coil. Now if we bring another coil near the first one, there will be an alternating

flux linkage with that second coil. As the flux is alternating, there will be obviously a rate of

change in flux linkage with respect to time in the second coil. Naturally emf will be induced in it

as per Faraday's law of electromagnet.

The winding which takes electrical power from the source, is generally known as primary

winding of transformer. Here in our above example it is first winding.

Fig3.5 transformer

The winding which gives the desired output voltage due to mutual induction in the transformer,

is commonly known as secondary winding of transformer. Here in our example it is second

winding

https://www.electrical4u.com/electrical-power-transformer-definition-and-types-of-transformer/

https://www.electrical4u.com/what-is-inductor-and-inductance-theory-of-inductor/#Mutual-Inductance

https://www.electrical4u.com/voltage-or-electric-potential-difference/

https://www.electrical4u.com/electric-power-single-and-three-phase/


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.

Fig 3.6 magnetic flux

2. Active Element

Definition: The elements which supply energy to the circuit are called Active Element. Those

devices or components which required external source to their operation is called Active

Components.

Examples: Diode, Transistors, SCR etc.

2.1. Diode

A diode: - is a device which only allows unidirectional flow of current if operated within a rated

specified voltage level. The name diode is derived from "di-ode" which means a device having

two electrodes.

The most common kind of diode in modern circuit design is the semiconductor diode.

Diode is a two-terminal device that allows current to flow in one direction, known as the

forward direction, when the anode of the diode has a higher positive potential than the

cathode. In this state, the diode is said to be forward biased.

If the polarity of the voltage is reversed, the diode is now reverse biased, and it will attempt to

block current flow, within its rated limits.

Diodes are often used as rectifiers to convert alternatingcurrent (AC) to pulsating, into direct

current(DC).

Symbol of Diode

The symbol of a diode is shown below, the arrowhead points in the direction of conventional

current flow


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Fig 3.7 symbol of diode

Working Principle of Diode

In a PN junction diode when the forward voltage is applied i.e. positive terminal of a source is

connected to the p-type side, and the negative terminal of the source is connected to the n-

type side, the diode is said to be in forward biased condition. We know that there is a barrier

potential across the junction. This barrier potential is directed in the opposite of the forward

applied voltage. So a diode can only allow current to flow in the forward direction when forward

applied voltage is more than barrier potential of the junction. This voltage is called forward


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biased voltage. For silicon diode, it is 0.7 volts. For germanium diode, it is 0.3 volts. When

forward applied voltage is more than this forward biased voltage, there will be forward current

in the diode, and the diode will become short circuited. Hence, there will be no more voltage

drop across the diode beyond this forward biased voltage, and forward current is only limited

by the external resistance" resistance connected in series with the diode. Thus, if forward

applied voltage increases from zero, the diode will start conducting only after this voltage

reaches just above the barrier potential or forward biased voltage of the junction. The time

taken by this input voltage to reach that value or in other words the time taken by this input

voltage to overcome the forward biased voltage is called recovery time.

Fig 3.8 p n junction of diode

2.2. Transistor

A transistor: A transistor is a device that regulates current or voltage flow and acts as a switch

or gate for electronic signals.it amplify or switch electronic signals and electrical power . It

consists of three layers of silicon or germanium semiconductor material. Impurities are added

to each layer to create a specific electrical positive or negative charged behavior. "P" is for a

positive charged layer and "N" is for a negative charged layer. Transistors are either NPN or

PNP in the configuration of the layers. There is no particular difference here except the

polarity of voltages that need to be applied to make the transistor operate.

http://www.electrical4u.com/diode-working-principle-and-types-of-diode/%3Ca%20href=


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Fig 3.9 principle of transistor

From the above figure, we can see that every BJT has three parts named emitter, base and

collector. JE and JC represent junction of emitter and junction of collector respectively. Now

initially it is sufficient for us to know that emitter based junction is forward biased and collector

base junctions is reverse biased.

2.3. The Silicon-Controlled Rectifier (SCR)

Silicon Controlled Rectifiers known commonly as Thyristors are three-junction PNPN

semiconductor devices which can be regarded as two inter-connected transistors that can be

used in the switching of heavy electrical loads. They can be latched-”ON” by a single pulse of

positive current applied to their Gate terminal and will remain “ON” indefinitely until the Anode

to Cathode current falls below their minimum latching level.

The operation of the thyirstor can be best explained by assuming it to be made up of two

transistors connected back-to-back as a pair of complementary regenerative switches as

shown.

Fig 3.10 thyirstor (SCR)


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3. Electromagnetic Devices

3.1. Relay

A relay is an electromagnetic switch operated by a relatively small electric current that can turn

on or off a much larger electric current. The heart of a relay is an electromagnet (a coil of wire

that becomes a temporary magnet when electricity flows through it).

It is similar to a Auxiliary contactor, which is used in generally control circuit, especially in PLC

for as a Digital input( feedback) or as a Digital out put to Switch on or off a electrical Contactor.

These are extremely useful when we have a need to control a large amount of current and/or

voltage with a small electrical signal Examples of relays thermal overload relay, time delay

relays etc.

Fig 3.11 Thermal overload relays

3.2. Contactors

A Contactor is a electromagnetic device which is used to make or break of any electrical

circuit.When a relay is used to switch a large amount of electrical power through its contacts,

it is designated by a special name: contactor. Contactors typically have multiple contacts,

and those contacts are usually (but not always) normally-open, so that power to the load is

shut off when the coil is de-energized. Perhaps the most common industrial use for

contactors is the control of electric motors.

http://www.explainthatstuff.com/electricity.html

http://www.explainthatstuff.com/magnetism.html


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Fig 3.12 contactor

There are two type of Contactor.

Power Contactor.

Auxiliary Contactor.

Power Contactor is used in power circuit like switch on/off of a motor,capacitor.while auxiliary

Contactor is used to switch on or off of a control circuit.

A power Contactor have 3 main contacts while a auxiliary contactor have many contacts like

1NO+1NC, 2NO+2NC

Where NC= normally closed contact

NO=normally open contact .

The number represents number of contacts on the relay

Power contactor is generally used where we required to make and break a large current

carrying circuit.


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4. Electrical protective device

1. Circuit breaker

A circuit breaker:- is an automatically operated electricalswitch designed to protect an

electrical circuit from damage caused by over current, typically resulting from an overload or

short circuit. Its basic function is to interrupt current flow after a fault is detected. Unlike a fuse,

which operates once and then must be replaced, a circuit breaker can be reset (either

manually or automatically) to resume normal operation.

Fig 3.13 breaker

2. Fuse

Fuse:-is a current interrupting device which protects an electrical circuit in which it is installed

by creating an open circuit condition in response to excessive current.

These fuses function to stop electricity from flowing to a particular component of the system by

creating an open circuit as a result of an unsafe electrical condition.

http://ask-the-electrician.com/electrical_circuit_breakers.shtml

https://en.wikipedia.org/wiki/Electricity

https://en.wikipedia.org/wiki/Electricity

https://en.wikipedia.org/wiki/Electrical_network

https://en.wikipedia.org/wiki/Overcurrent

https://en.wikipedia.org/wiki/Overcurrent

https://en.wikipedia.org/wiki/Short_circuit

https://en.wikipedia.org/wiki/Fuse_%28electrical%29

https://www.cableorganizer.com/electrical-fuses/


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Fig 3.13 fuse and its symbols


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Self-Check 3 Written Testand multiple choose


page:

1. Write example of active and passive elements /components(3 point)

2. One of the following devices is not protective device (1 pts)

A/ circuit breaker B/fuse C relay D/none

3. Semiconductor device used to Amplify electrical signal is (1pts)

A/diode B/transistor C/resistor D/all of the above

4. What is the different between resistor and transistor? (3 point)

5. What is the different between breaker and fuse? (2 point)

Answer Sheet

Name: _________________________ Date: _______________


1. ________________________________________________________________

________________________________________________________________

2. ________________________________________________________________

3. ________________________________________________________________

4. ________________________________________________________________

5. ________________________________________________________________

Note: Satisfactory rating - 5 points Unsatisfactory - below 5 points

You can ask you teacher for the copy of the correct answers.

Score = ___________

Rating: ____________


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Information Sheet-4 Tools and testing of electrical devices

Introduction

Test equipment is necessary for determining proper set-up, adjustment, operation, and

maintenance of electrical systems and control panels. The following is a general procedure for

use of test equipment:

4.1. Hand tools for electrical and electronic

I. pliers

When you need to grip, position, twist, cut, tighten or loosen various things, pliers can cover a

pretty broad range of applications. Because of their general design – consisting of two

handles, a pivot, and a head

Figure 4.1 plier and its parts

Types of pliers

1. Linesman plier


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Figure 4.2. lineman plier

Easily identified by the jaws, which have a shorter gripping surface towards the tip and a

cutting surface in the middle.This too can be used to bend, twist, and curt metal that might be

too tough for other pliers.

2. Combination Pliers

These multipurpose tools have three separate sections in the jaws. From the tip, the first

part is a serrated gripping surface. A round serrated section behind this makes gripping

tubes and other thick round objects easier. Finally, the section closest to the fulcrum

contains a cutting surface. Often mistaken for linesman pliers, the latter lacks a rounded

center section in the jaws.

Figure 4.3. combination plier

3. Slip Joint Pliers

Closely related to the adjustable wrench, these pliers have an adjustable fulcrum to alter the

width of the jaws. Many variants have notches for the fulcrum’s bolt to slip into when the jaws

are open, letting you lock on a specific width. They are often used for plumbing applications

and can perform many of the same duties as wrenches.

Figure 4.4. slip joint player

II. Screwdrivers

Screwdriver is driving hand tools used to tighten or loosen the nuts. It has been considered as

the one of the greatest inventions among tool.


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Long-nose pliers: Long-nose pliers are great for bending small loops at wire ends or for

cutting off wires (most include a wire-cutting section). Use the pointed end of the pliers to form

a smooth, 3/4 circle at a wire’s end, designed to circle around a screw terminal (always hook

the wire onto the terminal with the end of the bend sweeping clockwise from the wire).

Figure. 4.5 Long-nose pliers

Electrician knife: it has been specifically designed for the detail work of the electrician. It is

suitable for both normal wire stripping as well as for heavier duty cable work. There is an

integrated finger guard in the blade, which means you can get really close giving you better

feeling and greater control. Also the rubber handle gives you a firm and warm grip on the knife.

All these features contribute to safer knife handling and help to prevent work related injuries.

Fig 4.6. electrician knife

Types of screwdriver

There are many types of screwdrivers according to the design of the screw head drive or

recess type, but in this article we are going to discuss some common types of screwdriver

which are mostly used in every project.


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figure 4.7. different types of screw and screwdrivers

4.2. Testing/measuring Electrical devices

Measuring device is an instrument used to test or measure the quantities of electrical signals

Type of testing or measuring device

I. Multimeter:Is an electrical measuring instrument used to measure more than two

parameters i.e. it combines the voltmeter (for measuring volts), ammeter (amps) and

ohmmeter (ohms) and


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Figure 4.2.1 digital multimeter and its component


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Figure 4.2.2. analog multimeter

N.B. Red prob should be connected to VΩfand black prob is connected to common

II. Test light: is small device used to test the line current

Fig_4.2.3. _Circuit tester

III. Megger

Mega ohmmeter or megger is a special type of ohmmeter used to measure the

electrical resistance of insulators. Insulating components, for example cable jackets,

must be tested for their insulation strength at the time of commissioning and as part

of maintenance of high voltage electrical equipment and installations. For this

purpose meg ohmmeters, which can provide high DC voltages (typically in ranges

from 500 V to 5 kV, some are up to 15 kV) at specified current capacity, are used.

Acceptable insulator resistance values are typically 1 to 10 megaohms, depending

on the standards referenced.

https://en.wikipedia.org/wiki/Ohmmeter


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Figure 4.2.4 Megger


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Directions: Answer all the questions listed below. Use the Answer sheet provided in the

next page:

1. Write at list three electric testing devices. (2 point)

2. Write the main important tools for electrical work. (2 point)

3. What makes difference between Megger and ohmmeter? (2 point)

4. What is the main purpose of pliers? (2 point)

Answer Sheet

Name: _______________ Date: _______________


1. ________________________________________________________________

________________________________________________________________

2. ________________________________________________________________

________________________________________________________________

3. ________________________________________________________________

________________________________________________________________

4. ________________________________________________________________

________________________________________________________________



Score = ___________

Rating: ____________


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Operation Sheet 1 Electric circuit

Procedure of electric circuit connection

1. Wear PPE for safety

2. Look carefully the given diagram.

3. Identify the required tools and material.

4. Cut the electric wire and remove the insulation part

5. Check continuity of the wire

6. Connect one side both electric wires to the lamp holder negative and positive parts

7. Connect the other side to the battery negative and positive parts as shown on the

diagram

8. Install lamps to the lamp holder

9. Test the installed circuit

Name

:

_____________________________ Date: ________________

LAP Test Practical Demonstration


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Time started: ________________________ Time finished: ________________

Instructions: Given necessary templates, tools and materials you are required to

perform the following tasks within 1 hours.

Task 1 do the following diagram carefully.


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Instruction Sheet Learning Guide 48: Identify and Test

Electrical/Electronic Parts This learning guide is developed to provide you the necessary information regarding the following content

coverage and topics :

Following OHS policies and procedures

Checking Electronics system components & materials

Testing Rectifier, amplifier, filter

Testing Diodes, transistor, thyristor, and FET

Terminating and connecting Accessories

Doing Circuit test



Follow OHS policies and procedures

Check Electronics system components & materials

Test Rectifier, amplifier, filter

Test Diodes, transistor, thyristor, and FET

Terminate and connect Accessories

Do Circuit test





being discussed. Ask you teacher for assistance if you have hard time understanding

them.


5. Ask from your teacher the key to correction (key answers) or you can request your

teacher to correct your work. (You are to get the key answer only after you finished

answering the Self-check 1).

6. If you earned a satisfactory evaluation proceed to “Information Sheet 2”. However, if

your rating is unsatisfactory, see your teacher for further instructions or go back to

Learning Activity #1.


8. Read the information written in the “Information Sheet 2”. Try to understand what are


them.



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10. Ask from your teacher the key to correction (key answers) or you can request your

teacher to correct your work. (You are to get the key answer only after you finished

answering the Self-check 2).

11. Read the information written in the “Information Sheets 3 . Try to understand what are


them.




them.




them.







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Information Sheet -1 Following OHS policies and procedure

Introduction

Electricity is essential to modern life, both at home and on the job. Some employees --

engineers, electricians, electronic technicians, and power line workers, among them -- work

with electricity directly. Others, such as office workers and sales people, work with it

indirectly. Perhaps because it has become such a familiar part of our daily life, many of us

don't give much thought to how much our work depends on a reliable source of electricity.

More importantly, we tend to overlook the hazards electricity poses and fail to treat it with

the respect it deserves.

How do OHS standard minimize electrical hazards?

OHS standards focus on the design and use of electrical equipment and systems. The

standards cover only the exposed or operating elements of an electrical installation such as

lighting, equipment, motors, machines, appliances, switches, controls, and enclosures,

requiring that they be constructed and installed to minimize workplace electrical dangers.

Also, the standards require that certain approved testing organizations test and certify

electrical equipment before use in the workplace to ensure it is safe.

What is the best way to protect against electrical hazards?

Most electrical accidents result from one of the following three factors:

unsafe equipment or installation,

unsafe environment, or

unsafe work practices.

Some ways to prevent these accidents are through the use of insulation, guarding,

grounding, electrical protective devices, and safe work practices.

1.1 Safety Procedures and practices in electrical work

General guidelines and precautions as follows should be observed for safe working in

electrical installations.

Work on Low and Medium Voltage Mains and Apparatus

1. Unless a person is authorized to work on live low and medium voltage mains and

apparatus, all mains and apparatus to be worked upon shall be isolated from all

2. sources of supply, before starting the work, proved dead, earthed and short-circuited.

3. For earthling and short-circuiting, only recognized methods should be used. Measures

such as removing fuses shall be taken against the inadvertent energizing of the mains

and apparatus.

4. Only competent, experienced and authorized persons shall work on live mains and

apparatus, and such persons should take all safety measures as required under the

Rule.

5. Warning boards shall be attached on or adjacent to the live apparatus and at the limits

of the zone in which work may be carried out.


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6. Under no circumstances shall a person work with unsound hand gloves, mats, stools,

platforms or other accessories and safety devices.

1.2 General Precaution in Electrical Installation

It is always necessary to observe the following rules as precautionary measures in electrical

installations.

Avoid work on live mains which should be switched off before working.

Worninsulated footwear and rubber hand gloves are worn.

Avoid yourself against live conductors or apparatus.

In the event of near approach of a lightning storm, all outdoor work on electrical

system should be stopped.

Make a habit of being cautious. Be on the lookout for danger notice plates, danger

flags, warning boards and signals etc.

Never speak to any person working upon live mains or apparatus, on electrical

system

When working on high voltage try to keep your left hand in the pocket i.e. avoid your

left hand to get in contact with any live conductor or metallic casing of an apparatus

or metal pole or cross arms.


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Directions:Answer all the questions listed below. Use the Answer sheet

1. Who can affect with electrical hazard? (2 points)

2. What is the best way to protect against electrical hazards? (2 points)

3. What are safe work procedure in electric work?(2 points)

4. What are general precautions of electrical installation? (2 points)

5. How do OHS's standards minimize electrical hazards?(2 points)

Answer Sheet

Name: _________________ Date: _______________


1. ___________________________________________________________________

_______________________________________________________

2. ______________________________________________________________

______________________________________________________________

3. ___________________________________________________________________

_________________________________________________________

4. ___________________________________________________________________

_________________________________________________________

5. ___________________________________________________________________

____________________________________________________________

Score = ___________

Rating: ____________




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Information Sheet 2 Checking Electronics system components &

materials against jo requirement

Introduction to checking components

So you have to put a circuit together as far as you know everything appears to be ok , but

does not work as expected . Even worth it refuse to give any sign of life .

What do you do ? first check the circuits for mechanical failures like non-connected ,wire,

brokenvias on the board .bad battery contacts inside the case broken the pin on the

components .if this does not come up with a result you should compare values of

components schematics .you may have put a components in the wrong place or read

values the wrong way .

The fastest and simplest method to troubleshoot is to use an ohmmeter.

There are different type of electronics components to be checked such as contactors, relay,

transformer, fuse and breaker Diodes, transistor, thyristor, and FET Cables, lamps,

switches and junction box.

2.1. Contactors

Contactor is electromagnetic device energized when current is applied toit and deenergized

when current is interrupted. Contactors typically have multiple contacts, and those contacts

are usually (but not always) normally-open, so that power to the load is shut off when the

coil is de-energized. Perhaps the most common industrial use for contactors is the control

of electric motors.

Checking contactors

If the coil windings a contractor is burnt or open, the contactor is not energized .To check

this apply voltage to the contactor terminals and check it whether it is energized or not .If

energized it is working if not check with multimeter and replace with the same size of

contractors written on the name plate the name plate contains current rating , voltage rating

and the size of contactors example 380V/50A, 400v/60A, for three phase /480 Volts for

motors 1 horsepower or greater 220v/30A 120V/15A for single phase.The top three

contacts, switches the respective phases of the incoming 3-phase AC power, typically at

least 480 Volts for motors 1 horsepower or greater. The lowest contact is an

"auxiliary/holding" contact which has a current rating much lower than that of the large

motor power contacts i.e. 230V/10A, but it is actuated

by the same armature as the power contacts. One contactor may have several auxiliary

contacts, either normally-open or normally-closed.In any ways see carefully the name plate

of the system components while replacing. Example see the following table

The contactor ratings are based on maximum horsepower ratings as specified in the

National Electrical Manufacturers Association ICS2 standards. NEMA starters and

contactors are selected according to their NEMA size, from size 00 to size 9.


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2.2. Relay

Relays: is an electromagnetic switch that opens and closes a set of contacts when the

relay coil is energized. The relay coil produces a strong magnetic field which attracts a

movable armature bearing the contacts. They are mainly used in low-power circuits and

includes time-delay relays whose contacts open or close after a definite time interval. Thus,

a time-delay closing relay actuates its contacts after the relay coil has been energized. On

the other hand, a time-delay opening relay actuates its contacts some time after the relay

coil has been de-energized. Single-phase relays: 25A, 115/230V and 5A, 115V.

Checking of relay: when you want to replace relay first check the condition of relay by

using digital or analog multimeter between each pole of the relay and the corresponding

Normally closed (NC) and normally open (NO) contact for that pole all NC should read

infinite resistance when the relay is defective and then according to the rating written on

the name plate and size of the relay replace to the system components .In any ways check

the specified rate ,,size and types on the name plate of the system components while

replacing.


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Figure 2.1.Time delay relay and its indicator parts

Figure 2.2. (a) 8- pin base (b) 11-pin base time (c) on delay timer coil (d) off timer coil

Figure 2.3. relay and its internal parts

2.3. Transformer

A transformer is a static electrical machine which transfers electrical energy from one

circuit to another without changing the frequencies. raises or lowers voltage or current at

the same frequency.it requires an input of alternating current (AC).

Generally, there are two types of transformer in the market i.e. the linear type and switch

mode power transformer.


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Figure 2.4. linear type transformer device

Checking of transformer: Transformers are rated in volt-amperes (VA) or kilovolt amperes

(kVA). This means that the primary and the secondary winding are designed to withstand

the VA or kVA rating stamped on the transformer nameplate. The primary and secondary

full-load currents usually are not given. The installer must be able to calculate the primary

and secondary currents from the nameplate information. When the volt-ampere (or kilovolt-

ampere) rating is given, along with the primary voltage, then the primary full-load current

can be determined.

2.4. Diode

A diode is semi-conductor devices that pass current only in one direction. It has two

lead that acts as a one-way gate to electron flow. diode has p-type and n-type side.

The p-side is called anode and the n-side is called cathode. When the anode and

cathode of a pn-junction diode are connected to external voltagesuch that the potential

at anode is higher than the potential at cathode, the diode is saidto be forward biased.

In a forward-biased diode current is allowed to flow through the device. When potential

at anode is smaller than the potential at cathode, the diode is said to

be reverse biased. In a reverse-biased diode current is blocked.

Meter checking of a diode

Being able to determine the polarity (cathode versus anode) and basic functionality of

a diode is a very important skill for the electronics technician to have. Since we know

that a diode is essentially nothing more than a one-way valve for electricity, it makes

sense we should be able to verify itfrom the electronic catalog book(ECB)) the main

purpose of checking diode is to replace the dead diode with the same size, rating to

the system components according to specification of manufacturer company or type.


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Figure 2.5. different types and specification of diodes

Diode catalog specification

2.5. Transistors

A transistor is a linear semiconductor device that controls current with the application of a

lower-power electrical signal.it has three legs emitter, collector and base

Figure 2.6..BJT transistor: (a) PNP schematic symbol, (b) physical layout (c) NPN symbol,

(d) layout.


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Figure 2.7. (a) different types of transistor (b) transistor specfication type

Transistor acts as: an electrically controlled switch, ora current amplifier.it isanalogous to a

faucet. Turning faucet’s control knob alters the flow rate of water coming out from the

faucet. A small voltage/current applied at transistor’s control lead controls a larger current

flowthrough its other two leads.

The functional difference between a PNP transistor and an NPN transistor is the proper

biasing (polarity) of the junctions when operating. For any given state of operation, the

current directions and voltage polarities for each kind of transistor are exactly opposite each

other.

Figure 2.8. transistor as analogous to a faucet

N.B to identify the transistor legs use digital multimeter or catalog books

Checking of transistor

Steps by instruction


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1. Set the meter to its ohmmeter range and connect the base terminal of the transistor to

the terminal marked positive probe (Read) and negative or common (black probe)

terminal to the collector and then the meter reads open circuit (OL) for PNP transistor

2. Reverse the connection to base of transistor that means connecting the negative or

common(black) to base and connect the red probe to the collector and measure the

resistance and then take it to the emitter in both case the meter reds infinitive (OL) for

PNP transistor

3. Connect the negative terminal to the collector and positive terminal to the emitter

check that the meter read open circuit (OL) for both PNP and NPN.

4. Reverse the connection negative probe to emitter and positive probe to the collector

then the meter reads open circuits(OL).if the transistor pass all the test the it is basically

functional and all the junctions are unbroken.

2.6. Thyristor: - is a four-layer semiconductor device, consisting of alternating

P type and N type materials (PNPN). The

thyristor device works as a silicon-

controlled rectifier (SCR) so it can only

conduct current to one direction (see

AN4607It has three terminals: anode

(positive terminal), cathode (negative

terminal), and gate (control terminal). The

gate controls the flow of current between

the anode and cathode. The

primary function of a thyristor is to control electric power and current by acting as a

switch.

Checking of thyristor:) - like other electrical components thyristor has its own catalog

specification named on the name plate of the structure like transistors.

Filed effect transistor(FET):-is an electronic device which uses an electric field to control

the flow of current. FETs are devices with three terminals: source, gate, and drain. FETs

control the flow of current by the

application of a voltage to the

gate, which in turn alters

the conductivity between the

drain and source.

N.B to identify the terminal of

the transistor refere from ECEG

book of catalog

Self-Check 2 Written Test and multiple choose


Figure 2.7 thyristor device

Figure 2.8 typical specification of FET

https://en.wikipedia.org/wiki/Electronics

https://en.wikipedia.org/wiki/Electric_field

https://en.wikipedia.org/wiki/Electric_current

https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity


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1. What is the purpose of checking electronic components? (2 points)

2. How do you identify the terminal of transistors (2pts)?

3. What is the mechanism to check specification of Electronics components? on

the system connection

A/ by theirname plate B/ by multimeter C/ A and B D/ none

4. Where to check the transformer specification on the system components

A/ from ECEG book B/ from name plate C/ from national electric power D/ all

of the above

5. What is the difference between diode and transistor

A/ both are semi-conductor B/diode has two terminal C/transistors has three

terminal D/Band C

Answer Sheet

Name: _____________ Date: _______________


1. ______________________________________________________________

_____________________________________________

2. ______________________________________________________________

____________________________________

3. __________

4. ________

5. __________

Information Sheet 3 Testing of, Diodes, transistor, thyristor, and

FET

Introduction

Testing is the processes of checking electrical and electronics components whether they

are working or not.

Score = ___________

Rating: ____________




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Whenever you are working on any electronic equipment, your own safety has to come first.

Every electronic technician must always take safety precautions before he or she starts work.

Electricity must be handled properly, or else it can injure or cause fatalities. Here are some

basic steps that show you how to avoid accidents from occurring.

1.Electrical Shock:Once you open up a set cover, youíre actually exposing yourself to the threat

of electric shock. Always keep in mind that safety has to come

first. A serious shock may stop your heart and if large electric current flows through your body,

you will receive serious burns. Here are some rules, which should help you to avoid electricity

hazards.

Always turn off the equipment and unplug it before you begin to work.

If you have to run tests while the equipment is operating,

turn the equipment on, make your test carefully, and then turn the equipment off

again.

Wear rubber bottom shoes or sneakers.

Try to do the work with one hand, while keeping the other in your pocket. That

keeps the possible current paths away from the heart.

Don’t attempt repair work when you are tired or rushed.

Use only plastic screwdriver for shock protection during service operation.

Understanding Analogue and Digital Multimeter

Multimeters (analogue and digital) are one way in which you can seewhat is going on in an

electrical circuit. Voltmeters, ohmmeters, and ammeter are essential in all electric work. A

multimeter is as basic to an electronic technician as a brush is to a painter. How to connect a

meter and read these electrical circuit values is a fundamental skill that every electronics

repairers must know in order to successfully perform basic tests, troubleshooting and repairing.

Analogue and digital multimeters have either a rotary selector switch or push buttons to select

the appropriate function and range. Some Digital Multimeter (DMMs) are auto ranging; they

automatically select the correct range of voltage, resistance, or current when doing a test.


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Figure 3-1 analog multimeter function and rage components

If you are measuring voltage then select the AC (10V, 50V, 250V, or 1000V) or DC (0.5V, 2.5V,

10V, 50V, 250V, or 1000V) range. If you are measuring the resistance, selectthe Ohms range

(Rx1Ω, Rx10Ω, Rx100 Ω, Rx1kΩ or Rx10kΩ). If you are measuring the current then select the

appropriate current range (DCmA)


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Figure 3.2 digital multimeter function and range parts

Black test lead plugs into meter terminal marked Common, and Red test lead

plugs into meter terminal marked+ or V-Ω-mA.


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3.1. Testing of diode

Figure 3.3. diode and its terminal

Connectingthe red probe of your meter to the cathode and black probe to the anode, the

diode is forward biased and the meter should read some value of resistance. Touch the

black probe of your meter to the cathode and red probe to the anode, the diode is reverse

biased and should look like an open reading-the meter pointer not moving. If you get two

readings then most probably the diode is shorted or leaky and you should replace it.

Figure3.4 testing diode with analog meter

If you reverse the probes the pointer will not move at.


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(

3.2. T

e

s

t

i

n

g

T

r

a

n

s

i

s

t

o

r

Transi

stors

are

solid

state devices similar in some way to the diodes. The name transistor is derived from trans

resistor, meaning that it changes resistance. Unlike a diode, a transistor has three leads.

The three transistor leads are designated as Base (B), Collector (C), and Emitter (E). There

are two configurations for a common transistor: NPN and PNP as shown in Figure 1. Notice

the difference symbols for NPN and PNP transistor. The emitter arrow points away from the

transistor body for an NPN and toward the transistor body for PNP.

Figure3.5. (a) Forward biased (b) reverse biased with digital multimeter


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Figure 3.6 configuration of transistor

Testing transistor with analog or digital meter

Steps by instruction

1. Set the meter to its ohmmeter range and connect the base terminal of the transistor

tothe terminal marked positive probe (Read) and negative or common (black probe)

terminal to the collector and then the meter reads open circuit (OL) for PNP transistor

2. Reverse the connection

to base of transistor that

means connecting the

negative or

common(black) to base

and connect the red

probe to the collector

and measure the

resistance and then

take it to the emitter in

both case the meter

reds infinitive (OL) for

PNP transistor

3. Connect the negative

terminal to the collector

and positive terminal to

the emitter check that

the meter read open

circuit (OL) for both PNP and NPN.

4. Reverse the connection negative probe to emitter and positive probe to the collector

then the meter reads open circuits(OL).if the transistor pass all the test the it is basically

functional and all the junctions are unbroken.

Figure 3.7 testing transistor and checking legs


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3.3. Testing thyristor (silicon-controlled rectifier)

Testing SCR (silicon-controlled rectifier) can be done by using an analogue multi

meter or specialize tester . SCR consists of three pin of Gate (G), Anode (A) and

Cathode (C). In order to identify the pin out, one must find it from semiconductor

data book such the famous Philips ECG master semiconductor replacement

guide. The data book will list out the general specification of the SCR

such as the volt and ampere

Figure 3.8 thyristor symbol and configuration


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Figure 3.9. testing of thrystor with analog meter

Removing the black probe from the GATE pin (the black probe still touching the Anode pin)

you would noticed that the resistance continues to be there (low resistance). This is due to the

conduction of SCR as the meter battery is usually able to supply current more than the

holding current. If at this stage you removed theblack probe from the Anodepin and connect it

back, thepointer will dropped back toinfinity (high resistance). If theSCR could hold the

resistancethen the SCR is consideredgood. If it can’t hold then theSCR is faulty.

3.4. Testing filed effect transistor (FET)/MOSFET

Figure3.10 FET and its component configuration

The right way of testing mosfet transistor is to use an analogue multimeter. MOSFET stand for

Metal oxide semiconductor field effect transistor or we just called it FET. Switch mode power

supply and many other circuits use FET transistors as part of a


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Figure

3.11 different method of testing FET

circuit. Touch the gate pin with the red probe to discharge any internal capacitance in the

mosfet. Now move the red probe to source pin while the black probe still touching the drain

pin. Use your right finger and touch the gate and drain pin together and you will notice the

analogue multimeter pointer will move forward to centre range of the meter's scale.


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Self-Check 3 Multiple choose


1. The material used to check the function electronic components is? (2 points)

A/ ohmmeter B/megger C/A and B D/ none

2. What is the importance of testing electronic system components? (2 points)

A/ to identify broken material B/ to check the functionality of components

C/ to identify the problem D/ all.

3. One of the following is not electronic components

A/ transistor B/ diode C/ relay D/ none

4. One of electronic components is used as amplifier and switch

A/ diode B/ transistor C/ capacitor D/All

Answer Sheet

Name: ________________ Date: _______________


1. _____________________________________________________________

2. ______________________________________________________________

3. ______________________________________________________________

4. ______________________________________________________________

Score = ___________

Rating: ____________




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Information Sheet -4 Terminating and connecting accessories

Introduction to

wire termination and connecting accessories

A wire termination is the work performed to the end of a wire that allows it to connect to a

device (connector, switch, terminal, etc.)

When terminating multicore cables,there are some basic rules of goodpractise to follow.

It should have sufficient length. This is very important when wire or cable to re-

terminate.Because unscrew an existing accessory and find it difficult to disconnect and

connect a new fitting because the previous installer cut the conductors too short.

6. Good Mechanical protection

As well as the length of

conductors,weneedtoallowsufficientmec

hanical protection of the cablesentering

the

box.Thisallowsformovementwhiletermin

ating without damaging theprotection

afforded by the greyPVC

.Approximately

10mmofoutersheathingintotheaccessor

y box. This affords

usadditionalprotectionfrommechanical

damage.

4.1. Terminal Lugs

A terminal may be attached to a wire by

a number of methods including screw-on, press-on or crimp-on. Selection is based on two

main criteria ; the wire size the barrel is designed to accept and the tongue with will fit a

particular stud size. The barrel may be insulated or non-insulated. Normally both insulated

or non-insulated should have the

wire crimped on,

but in some cases

the non-insulated

lugs may be

soldered. There

are a number of

styles including

three and four

way. The eyelet

may be Ring,

Block Spade,

Fig 5.1 wire color and length

Figure 4.1 (a)Pre insulated Terminal Lug

Figure 4.1 (b)Terminal Lug attached to a Terminal Stud


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Spring Spade, Flanged Spade, or Hook. Some terminal lugs also have two eyelets.

There are four main types of

terminal lugs;

Basic Terminal with insulated nylon

support sleeve.

Basic terminal with permanently

attached insulating sleeve.

Basic terminal bonded with silver

brazing alloy.

Basic terminal with butted seam

4.1.1. Terminal blocks

A terminal block (also called as connection terminal or terminal connector) is a

modular block with an insulated frame that secures two or more wires together. It consists

of a clamping component and a conducting strip. A typical simplest terminal block is as

shown in the image below.

The insulating body of a terminal

block houses a current carrying

element (a metal strip or terminal

bar). It also provides a base for

clamping element. The body has

a mounting arrangement so that

the block can be easily mounted

on or unmounted from a PCB or

a mounting rail.Terminal blocks

keep connections much more secure and wires well organized.

4.1.2. Types of Terminal Blocks

Electrical terminal blocks can be classified on the basis of structure, device type,

termination options etc.

4.1.2.1. Structure type

Single level pass-through terminal blocks These are simply used to connect two wires

together, i.e. wire-to-wire connection. These are also called as single feed terminal

blocks. Single level terminal blocks are of the most simple type having one input contact

and one output contact.

Dual level terminal blocks These blocks have another level of connection terminal

stacked on the first one. This arrangement is generally used to save space.

Three level terminal blocks Just like dual level blocks, these have an extra level at

the top. An advantage of using multilevel blocks is that multiple connections can be

made in the same block.

Figure 4.1(c) Terminal Lug Assembly

Figure 4.2.Terminal block


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Fig

ure

4.3.(b) dual terminal block Figure 4.3.(c) three level terminal block

4.1.2.2. Device Type

Ground Terminal Blocks

These blocks often look like a single level feed through terminals. The exception is that

these blocks and the metal connection where the wire is terminated are grounded to the

panel or DIN rail on which the block is mounted.

(a) (b)

Figure 4.3 (a)Single level pass through terminal block

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Figure 4.4(a) ground terminal block Fgure 4.4.(b) Fuse connection terminal

block

Fused Connection Terminals

These are similar to the pass-through blocks with an exception of the metal connection strip

is replaced with a fuse. Therefore, the wires will be connected through a fuse providing an

added protection.

4.1.2.3. Clamping Options In Terminal Blocks

Screw terminal:- are the most common type of connection method. The wire or

conductor is simply pressed against the conductor strip in the block by tightening the

screw. Screw terminals accommodate a very wide range of wire or conductor sizes.

Spring clamp:- These type of terminals use spring pressure to retain the wire

clamped. Spring clamps are a newer alternative to screw clamps and are generally

used for relatively small wires.

Figure 4.5 spring clamp terminal block

4.2. Electrical Accessories

The items used in domestic and industrial electrical wiring are called electrical accessories,

e.g., switch, holder, socket, plug-top, ceiling rose, fuse cut-out etc. A switch is used to make

a circuit ON and OFF. A holder is used with a lamp, a ceiling rose is used with a ceiling fan,

tube light or a pendant lamp. A socket is used to provide main supply to a portable

appliance, such as, table fan, table lamp, electric iron, radio, T.V. etc. A fuse cut-out is used

to stop an excess flow of current in a circuit.

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6. Switch

A switch is used to make or break the electric circuit. It should so operate that it must make

the circuit firm. At the instant of breaking the switch it should break the current so that there

is no formation of arc between the switch blades and contact terminals. Formation of arc

burns or damages the switch contacts. Such an arc is avoided usually by means of

providing a spring to movable blade so as to have a quick action.

Ther

e

are

four

type

s of

switc

hes.

1.

Tum

bler

switc

h

2.

Flus

h

switc

h

3.

Knif

e

switc

h

1. T

u

m

b

ler Switch

It is a 5 ampere current rating switch which is used in domestic electrical wiring. It is also

known as a surface switch. It can be fitted on a wooden board or a round block. The type of

tumbler switches are as follows:

I. Single Way switch. This switch is provided with a single pole to control one light

point at a time (i.e., a lamp, fan, tube-light etc.). It may be round or rectangular in

shape.

II. Two-way Switch. These are used for wiring circuits which are to be controlled from

two points independently such as stair wiring, bedroom and godown.

Figure 4.6 different type of switches


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III. Intermediate Switch. It is used along with a two way switch to control a lamp etc. for

more than two places.

IV. Bed Switch. It is a hanging type single way switch is used with bed lamps.

V. Grid Switch. The grid switches are similar to tumbler switches, except that they are

lighter and are portable type, so they are used for the portable machines such as

hand drill, portable grinder, etc. They are manufactured either in single-way or in

two-way pattern both for 5 and 15 amperes.

VI. Duplex Switch. It is also used in machines.

VII. Bell Push Switch. It is spring type single way switch which is used with an electric

bell to make the circuit ON for a very short time.

VIII. Rotary Switch. These switches are much different from the ordinary tumbler

switches. These switches are used for hot plates voltage stabilizers, etc., where may

tapping’sbe taken.

7. Lamp holders and their Types

As the name shows, a lamp holder is used to hold the lamp required for lighting purpose.

These holders can be classified as:

(i) Bayonet cap lamp holders which can further be subdivided into:

(a) Pendent holder: used for hanging lights up to 250 watts.

(b) Batten holder: used for wall fixed lights up to 250 watts.

(c) Screwed holder which when used with a bracket is called as bracket holder-up to 250

watts lamp.

(d) Water-tight bracket.

(ii) Switched Bayonet cap lamp holders used for table lamps.

(iii)Screw lamp holders: These types of holders are used with screwed type, lamp up to

1000 watts 250 volts.

(iv) Fluorescent lamp (Tube) holders: These are either bi-pin type or of bayonet cap type,

but pin type holders are generally used.


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Figure 4.7 different types of lamp holder

8. Pin Plug

It is used for connecting a portable appliance, example; Table fan, table lamp, electric iron,

radio, T.V. etc. to a socket. It may be two or three pin type. A two-pin plug is used at 5 or 15

amperes. The third pin is the earth line pin and it is thicker than the two other pins. It is also

made of Bakelite. A pin-plug is also known as a plug-top.

9. Socket

Socket has an insulated base with molded or socket base having 3-terminal sleeves. The

two thin terminal sleeves are meant for making connection to the cable with the third

terminal sleeve thicker in cross-section is used for earth connection. The cover is again

molded and has corresponding 3 holes. These are made for 5 amps and 15 amps load.

Examples of electrical accessories


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Figure 4.8 two pin top and three pin top socket out let

10. Fuses

Fuse is a device which cuts off the circuit when more than predetermined value current

flows in a circuit.

It is the weakest point of the circuit which breaks when more than normal current flows in

the circuit.

Fuse wire: The function of the fuse wire is to carry the normal working current safely without

heating but when more than normal working current passesthrough it, rapidly heats up to

melting point.

The materials which can be used in fuse are tin, lead, zinc, silver, antimony, copper,

aluminum etc. Copper or lead, tin alloy is mostly used in ordinary fuse wire.

Figure 4.9 (a) wire fuse (b) Cartridge Fuse Cut-out

11. Circuit breaker

A miniature circuit breaker(MCB) is an electromechanical device which operatesand

disconnects the circuit when the current reaches a predetermined value.. MCB is a


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replacement for a fuse with most accurate and efficient system in overload and short

circuit protection. In fact it provides overload protection and short circuit protection

whereas a fuse offers short circuit protection only.

Operation: The MCB is a high fault capacity thermal / magnetic, current limiting trip free

automatic switching device with just magnetic tripping. There are two main operations

i.e., thermal operation with inverse time current characteristics for overload protection

and hammer trip assisted magnetic operation for short circuit protection

Figure 4.10 Different types of circuit breaker


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Self-Check – 4 Written Test and multiple choose

Directions: Answer all the questions listed below. Use the Answer sheet provided in the

next page:

Writing questions

1. What does mean is terminating of wire ?

2. What are electric accessories? Mention their uses.

3. Write the types of switches and their function?

4. Mention the types of Lamp holders

5. What is socket? Mention the types

Multiple Choose

6. One or more turns, usually roughly circular or cylindrical, of current-carrying wire

designed to produce a magnetic field is called

A. coil B. cable C. relay D. contactor

7. The material that use to transmit electric current

A. motor B. Pump C. wire and cable D. A and B

8. the wire color that use for grounding only.

A. black B. red C. white D. green &bare copper

9. The modular block with an insulated frame that secures two or more wires together

A. terminal lug B. terminal block C. wire marker D. All

10. Electrical terminal blocks can be classified on the basis of

A. structure type B. device type C. termination options D. All

Answer Sheet

Name: _____________ Date: _______________


1. ________________________________________________________

2. ________________________________________________________

3. ________________________________________________________

4. ________________________________________________________

5. ________________________________________________________

6. ____ 9______

7. ____ 10______

8. ____

Score = ___________

Rating: ____________



https://www.britannica.com/science/magnetic-field


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Information sheet-5 Doing Circuit Test

Introduction

Circuit test the processes of testing different electrical and electronic components in the

circuits. there are several testing device /tools you can use tocheck for continuity.i.e a

completed circuit. A continuity tester is the simplest tool for specific task of checking

continuity . while amultimeter also provides a wide range of other electrical testinguses. you

can also use a circuit tester to check for community. but best use is checking for proper

grounding of your circuits. Different types of circuit test

1. Resistance test

2. Continuity test

3. LED Test

4. Ground test

2. Resistance and Resistors

The word resistance means opposition to some action. In electricity resistance means the

opposition to the flow of current. The resistance is measured in ohm (Ω). Resistance is also

expressed in kilo-ohms, milliohms etc. With 1000Ω = 1 kilo ohms, 1000000Ω = 1 mega ohms.

Figure 5.1 (a) symbol of resistance (b) resistor

The main two characteristic of resistor are its resistance R in ohms and its

power rating in watts, W. Resistors are available in a very wide range of

R values from a fraction of an ohm to many mega ohms.

The power rating may be as high as several hundred watts or as low as 1/8 watt.

Always use a replacement resistor with a power rating that is equal to or greater than

the original. The value of the resistance can be measure by a multimeter.

Types of Resistor


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i. Carbon-Composition Resistors

ii. Carbon-Film Resistors

iii. Metal-Film Resistors

iv. Wire Wounds

v. Fusible Resistor

vi. Variable Resistor

Figure 5.2 Different types of resistor

Because carbon resistors are small physically, they are color coded mark their R value in

ohms. In memorizing the colors, note that the darkest colors, black and brown, are for the

lowest numbers, zero and one, through lighter colors to white for nine. You must know

thiscode.


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Figure 5.4 Color code resistor and their corresponding values

Testing resistor

There are two ways of testing resistor; using an analogue or digital multimeter. Normallyif a

resistor fails they will either increase in value or open up at all (open circuit). You can check

the resistor resistance by selecting the ohmmeter range in the analogue and digital

multimeter.


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Figure 5.5 Testing resistor with analog meter

Figure 5.6 Testing resistors with digital meter

3. Continuity test

Continuity or short circuit test Continuity checks ensure a reliable, low resistance connection

between two points. For example, check the continuity of a cable between two connectors to

ensure that both ends are connected properly. Set your analogue multimeter to a low

resistance scale (X1 Ohms), short (touch) the red and the black probes together, the pointer

will go to zero ohm. If it is not zero, adjust the zero adjuster for bringing the pointer to exact


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zero ohms. When checking for continuity, make sure the ohmmeter is set on the lowest

ohms range.If continuity exists between two points, the ohmmeter will read a very low

resistance such as zero ohms.

If there is no continuity between two points, the ohmmeter will read infinite ohms

Figure 5.7 checking the continuity of cable with analog

Figure 5.8 checking the continuity of cable with digital

4. Testing Light Emitting Diode (LED)

Light emitting diode (LED) is a diode that produces light when current flows through it, when it

is forward bias. The LED does not emit light when it is revered-biased. The LED is used as a

low current indicator lamp in many types of consumer and industrial quipments, such as

monitors, TV, printers, hi-fi systems and machinery control panels.

The plastic lens is very important in directing and modifying the small amount of light emitted


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by the LED chip. Light can be visible, such as red, green, yellow and white. It is label as LEDin

circuit board. An LED only needs about 2v across its anode and cathode terminals to make it

emit light. If a higher voltage is used, the current which flows through it may be high enough to

damage it. In order to limit current when an LED is used at higher voltages, a resistor must be

connected in series with it.

The cathode of the LED is identified on the package by the flat side on the plastic. The life

expectancy of LED is about 100,000 hours.

Figure 5.9 General appearance and Symbol for a light emitting diode

Testing LED

Remember that the LED only emits light when it is forward bias and the LED does not emit

light when it is revered-biased. If LED does not emit light when it is forward bias then it has

developed an open circuit and should be replaced. Power must be off when check the LED.

Figure 5.10 Testing LED with analog

5. Ground test: the connection to ground provides a shortcut back to the source. ground

is typically any major metal parts in electrical and electronics circuits.it provides a

common connection that all circuits can be use so that they do not have to be wired all

the back to the source.


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Figure 5.11 grounding metal

Figure 5.12 checking earth ground with testing device


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6. Testing of transistor and diode(refer LO- information sheet-3 for more)

Figure 5.12 Testing PNP transistor

PNP Test Procedure

Connect the meter leads with the polarity as shown and verify that the base-to-emitter and

base-to collector junctions read as a forward biased diode: 0.5 to 0.8 VDC.

Reverse the meter connections to the transistor and verify that both PN junctions do not

conduct. Meter should indicate an open circuit. (Display = OL.) • Finally read the

resistance from emitter to collector and verify an open circuit reading in both irections.

(Note: A short can exist from emitter to collector even if the individual PN junctions test

properly.)


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Figure 5.13 Testing NPN transistor

NPN Test Procedure

Connect the meter leads with the polarity as shown and verify that the base-to-emitter and

base-tocollector junctions read as a forward biased diode: 0.5 to 0.8 VDC.

Reverse the meter connections to the transistor and verify that both PN junctions do not

conduct. Meter should indicate an open circuit. (Display = OL.)

Finally read the resistance from emitter to collector and verify an open circuit reading in

both directions. (Note: A short can exist from emitter to collector even if the individual PN

junctions test properly.)

7. Testing contactor

Contactors are used to remotely switch electrical power. The coil-actuated switch operates

exactly like a relay, but a contactor typically handles higher amperages in the switch

mechanism itself. The coil consists of many winds to a wire and is energized by a smaller

voltage. A movable solenoid, called a plunger, is mechanically connected to a set of spring-

loaded copper discs. These discs are called the contacts. When the coil is energized, the

solenoid pushes against the spring and closes the contacts. When the coil voltage is

removed, the force of the spring returns the contacts to their normally open position. For

this point you will need to use a multi-meter to verify coils resistance. This resistance value

should between some Ohms to kOhms this depends of coils voltage and contactor models


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Figure 5.15 Part of contactors

Figure 5.15 Testing of contactors

Figure 5.13.a If you found a value close less than 0.1 ohms you are facing a coil short

circuit


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Figure 5.13.b If you have an infinite value you are facing an open coils circuit

8. Testing of relay

An electromagnetic relay is basically a switch operated by magnetic force. This

magnetic force is generated by flow of current through a coil in the relay. The relay opens or

closes a circuit when current through the coil is started or stopped. The specification of

relay normally are 5V, 12V, 18V, 24 V and etc and with amperes rating too.

Figure 5.16 Typical relay circuit symbol of relay and

To check the relay coil's resistance, take the multimeter you have and place it in the

ohmmeter (Ω) setting and place the probe leads of the multimeter on the 2 terminals of the

relay's coil. It doesn't matter which probe is placed on which terminals. Resistance isn't

polarized.

If you read a value about the rated coil resistance, the coil works and should function

correctly. If you read a very low resistance and very high resistance, the coil is either

shorted or is open. In this case, since coils normally are not repaired, you must simply

replace the relay.

Figure 5.17 Testing of terminal relay


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Testing NC (Normally Closed) Terminal of a Relay

The relay's Normally Closed Terminal should read near 0Ω from the NC (Normally Closed)

terminal to the COM (common) terminal, when the relay has no voltage going through it.

This is because the NC terminal is normally closed, meaning there should be direct

continuity from the NC terminal to the COM terminal when the relay isn't energized; thus,

there is almost 0Ω resistance between the 2 terminals.

Take out a multimeter and place it in the ohmmeter (Ω) setting. Place one probe on the

COM terminal and the other probe on the NC Terminal. Make sure that you read a

resistance of near 0Ω. If you do, then the NC Terminal reads the correct resistance and

should function properly.

How To Test the NO (Normally Open) Terminal of a Relay

The relay's Normally Open Terminal (in double throw relays) should read a very high

impedance (several megohms (MΩ)) from the NO (Normally Open) terminal to the COM

terminal. This is because the NO terminal is normally open, meaning there's no direct

connection from the NO terminal to the COM terminal when the relay isn't energized; thus,

there is an extremely high impedance between the 2 terminals.

Take out a multimeter and place it in the ohmmeter (Ω) setting. Place one probe on the

COM terminal and the other probe on the NO Terminal. Make sure that you read a high

resistance of several megohm (MΩ). If you do, then the NO Terminal reads the correct

resistance and should function properly.

9. Push button

A pushbutton is a control device used to manually open and close a set of contacts.

Pushbuttons may be illuminated or nonilluminated, and are available in a variety of

configurations and actuator colors. Pushbuttons are used in control circuits to perform

various Pushbuttons functions; for example, starting and stopping a motor. A typical

pushbutton uses an operating plunger, a return spring, and one set of contacts.

Normally open (NO) pushbutton. Normally the contacts are open and no current flows

through them. Depressing the button causes the contacts to close. When the button is

released, the spring returns the plunger to the open position.


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Figure 5.18 Normally open pushbutton

Normally closed (NC) pushbuttons: are also used to open and close a circuit. In this

pushbutton’s normal position, the contacts are closed to allow current flow through the

control circuit. Depressing the button opens the contacts, preventing current flow through

the circuit. These types of pushbuttons are momentary contact pushbuttons because the

contacts remain in their activated position only as long as the plunger is held depressed

Figure 5.20 Normally closed pushbutton

Testing pushbutton is like testing continuity


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Self-Check – 5 Written Test and multiple choose

Directions: Answer all the questions listed below. Use the Answer sheet provided in the next page:

1. Which one of the following is used to test electronic components? (1pts)

A/ analog multimeter B/ digital multimeter C/ ohmmeter D/ all

2. One is used as rectification which one is it (1pts)

A/ diode B/ transistor C. resistor D/ capacitor

3. One of the following is not true (1pts)

A/ transistor act as switch B/ transistor act as amplifier C/diode actas rectifier D/ diode

act amplifier

4. The main purpose troubleshooting electrical-electronics is (1pts)

A/ to identify the faults B/ to replace the component C/ repair the components D/all

5. What is continuity test ?(2pts)

6. What is the difference between diode and transistor? (3pts)

7. Write the difference between resistance and resistor? (4pts)

Answer Sheet

Name: ____________________ Date: _______________


1. __________

2. __________

3. __________

4. __________

Score = 9pts

Rating: ____________


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5. _____________________________________________________________________________

___________________

6. _____________________________________________________________________________

___________________________________________________________

7. _____________________________________________________________________________

__________________________________________________________

Operation sheet 1 Diode testing

Name: _____________________________ Date: ________________


Direction: Diode testing

Equipment, tools and materials:

Manufacturer’s maintenance manual, Procedures, paper, pen, pencil, learning guide

Instruction:



3. Make all power to the circuit is OFF

4. Turn the dial (rotary switch) to Diode Test mode ( ).

5. Connect the test leads to the diode.

6. Record the displays displayed.

7. Reverse the test leads.

8. Record the measurement displayed.

9. Determine the forward and reverse biased (cathode and anode )


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Operation sheet 2 Contactor testing

Name: _____________________________ Date: ________________


Direction: Contactor testing

Equipment, tools and materials:

Manufacturer’s maintenance manual, Procedures, paper, pen, pencil, learning guide

Instruction:



3. Make all power to the circuit is OFF

4. Identify the rating of contactors (current voltage, and power )

5. Turn ON testing device and dial (rotary switch) to Diode Test mode ( ).

6. Connect the test leads to coil terminal of each(A1-A2)

7. Measure the resistance of the coil and compere with rated values of the coil resistance

8. Connect the test leads to main contactor terminals and check the continuity (shows

normally open )

9. Press down the plunger and test the main contactor terminals (become closed)

10. Justify your work

Name: _____________________________ Date: ________________


Instructions: Given necessary templates, tools and materials you are required to perform

the following tasks within 1 hours.

Task1. Test diode

Task2. Test transistor

Task3. Test contactor and pushbutton



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Instruction Sheet Learning Guide 49: Test the construction of

electrical/ electronic circuits

This learning guide is developed to provide you the necessary information regarding the

following content coverage and topics –

Reading Electrical power circuit diagram and preparing control circuit diagram

Testing cable laying, joint, lamps, switches and junction box.

Selecting cable size.



Read Electrical power circuit diagram and prepare control circuit diagram

Test cable laying, joint, lamps, switches and junction box.

Select cable size.






4. Accomplish the “Self-check 1” in page17.



Self-check 1).

3. If you earned a satisfactory evaluation proceed to “Information Sheet 2”. However, if your

rating is unsatisfactory, see your teacher for further instructions or go back to Learning

Activity #1.


5. Read the information written in the “Information Sheet 2”. Try to understand what are being

discussed. Ask you teacher for assistance if you have hard time understanding them.

6. Accomplish the “Self-check 2” in page 34



Self-check 2).






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Information Sheet -1 ReadingElectrical power circuit diagram

preparing control circuit diagram

Introduction

Power is the rate at which electrical energy is consumed in electrical circuit. The unit

measurement iswatt. There are two types electric power

Alternating current (Ac) and Dc Power supply

AC means Alternating Current and DC means Direct Current. AC and DC are also used

when referringto voltages and electrical signals which are not currents! For example: a 12V AC

power supply has analternating voltage (which will make an alternating current flow). An

electrical signal is a voltage orcurrent which conveys information, usually it means a voltage.

The term can be used for any voltage orcurrent in a circuit.

Alternating Current (AC) flows one way, then the otherway, continually reversing direction.

An AC voltage is continually changing betweenpositive (+) and negative (-).The rate of

changing direction is called the frequencyof the AC and it is measured in hertz (Hz) which is

thenumber of forwards-backwards cycles per second.

Figure 1.1 AC frequency signal

Amplitude is the maximum voltage reached by the signal.

It is measured in volts, V.

• Peak voltage is another name for amplitude.

• Peak-peak voltage is twice the peak voltage (amplitude). When reading an oscilloscope

trace

it is usual to measure peak-peak voltage.

• Time period is the time taken for the signal to complete one cycle.

It is measured in seconds (s), but time periods tend to be short so milliseconds (ms) and


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microseconds (μs) are often used. 1ms = 0.001s and 1μs = 0.000001s.

• Frequency is the number of cycles per second.

Dc current is conventional current i.e. it flows only in one direction current always from

negative to positive and it has no frequency.

A DC voltage is always positive (or always negative), but it may increase and decrease.

Electronic circuits normally require a steady DC supplywhich is constant at one value or a

smooth DC supplywhich has a small variation called ripple.

Figure 1.2. Dc signal

The difference between Ac and Dc

Figure 1.3. DC VS alternating current


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1. Reading Electrical power circuit and control circuitsdiagram

Typically, two types of circuits are used in motor control system.

1.1. Power circuit diagram

1.2. Control circuit diagram

1.1. Power circuitsis defined as any circuits used to carry electrical power that

operates the load. Power circuits are the connections to motor, magnetic contactor

carrying high current and overload relay.

There are different types of motor power circuit diagram

Direct on line (DOL)

AC vs. DC

Advantage Disadvantage

Alternating

current

1. Simpler to transmit since generators at the

power plants produce AC Voltage and currents

2. Greater power can be generated using turbines

3. Can be transmitted over long distances easily

4. Readily Scalable to any desired voltage

5. Power can flow it two directions (Positive and

negative) and a number of different phases (2-

phase, 3-phase

1. More dangerous to

transmit than DC.

Requires transformersand

substations.

2. Causes

electromagnetic

interference

can you think of more?

Direct

current

(DC)

1. Reactance. DC system does not introduce a

reactance in the line.

2. Power In DC system, the power is just the real

component.

3. Frequency In DC system, the frequency is zero,

thus no frequency variation to monitor.

4. Analysis Analysis of AC system always involved

complex numbers, while DC is only a real number,

thus simplifying the analysis.

5. NO skin effect. A DC system has no skin effect

so we can utilize entire cross section area of line

conductor.

1. unable to scale voltage

and current efficiently

2. Large amounts of

power is lost due to the

resistivity of the wire in

long distance DC

transmission

can you think of more?


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Star-delta

Autotransformer etc.

A. Direct on line (DOL)

The Direct On-Line (DOL) starter is the simplest and the most inexpensive of all starting

methods and is usually used for squirrel cage induction motors. It directly connects the

contacts of the motor to the full supply voltage. The starting current is very large,

normally 6 to 8 times the rated current. The starting torque is likely to be 0.75 to 2 times the full

load torque. In order to avoid excessive voltage drops in the supply line due to high starting currents, the

DOL starter is used only for motors with a rating of less than 5KW

Figure 1.4. DOL power circuits

B. Star -delta


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Figure 1.5. star delta connection

The star delta starting is a very common type of starter and extensively used, compared to the

other types of the starters.

This method used reduced supply voltage in starting. Figure(2) shows the connection of a

3phase induction motor with a star –delta starter.

The method achieved low starting current by first connecting the stator winding in star

configuration, and then after the motor reaches a certain speed, throw switch changes

the winding arrangements from star to delta configuration. By connecting the stator windings,

first in star and then in delta, the line current drawn by the motor at starting is reduced to one-

third as compared to starting current with the windings connected in delta. At the time of

starting when the stator windings are start connected, each stator phase gets voltage

where VL is the line voltage. Since the torque developed by an induction motor is

proportional to the square of the applied voltage, star- delta starting reduced the starting torque

to one – third that obtainable by direct delta starting.


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Figure 1.6. star-delta power circuit diagram


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C. Auto-transformer

The operation principle of auto transformer method is similar to the star delta starter method.

The starting current is limited by (using a three phase auto transformer) reduce the initial stator

applied voltage.

The auto transformer starter is more expensive, more complicated in operation and bulkier in

construction when compared with the star – delta starter method. But an auto transformer

starter is suitable for both star and delta connected motors, and the starting current and torque

canbe adjusted to a desired value by taking the correct tapping from the auto transformer.

When the star delta method is considered, voltage can be adjusted only by factor of

Figure 1.7 auto-transformer power circuit diagram

1.2. Control circuit:- the control circuit can operate the same voltage as the

powercircuits, but it can operate at lower voltage by using machine tool transformer to

step down the voltage to convenient level. Control circuit is the part of the circuit where

panel switches, limit switches and sensors are connected to control large machines.


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Figure 2.1. Motor control panel

1.2.1. Basic Components for Control Circuits

a. Disconnecting switches: isolates the motor from the power source. It consists of 3 knife-

switches and 3 line fuses enclosed in a metallic box. The knife-switches can be opened

and closed simultaneously by means of an external handle. An interlocking mechanism

prevents the hinged cover from opening when the switch is closed. Disconnecting

switches (and their fuses) are selected to carry the nominal full-load current of the mo tor,

and to withstand short-circuit currents for brief intervals.

b. Circuit breakers opens and closes a circuit, like a toggle switch. It trips (opens)

automatically when the current exceeds a predetermined limit. After tripping, it can be

reset manually. Circuit breakers are often used instead of disconnecting switches because

no fuses have to be replaced. It is rated in 400v/50A, 220/25A etc.

Figure 2.2.. circuit breaker and its symbol

Push-buttons:-A pushbutton is a switch activated by finger pressure. Two or more contacts

open or close when the button is depressed. Push-buttons are usually spring


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loaded so as to return to their normal position when pressure is re moved. Mechanical-

interlocked push buttons with NO (normally open) and NC (normally closed) contacts; rated to

interrupt an ac current of 6 A one million times.

Figure 2.3. push and its symbol

C. Control relays: is an electromagnetic switch that opens and closes a set of

contactswhen the relay coil is energized. The relay coil produces a strong magnetic field

which attracts a movable armature bearing the contacts. They are mainly used in low-power

circuits and includes time-delay relays whose contacts open or close after a definite time

interval. Thus, a time-delay closing relay actuates its contacts after the relay coil has been

energized. On the other hand, a time-delay opening relay actuates its contacts some time

after the relay coil has been de-energized. Single-phase relays: 25A, 115/230V and 5A,

115V.


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Figure 2.4. different time- relay series


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Figure 2.5. components of timer -delay relay

D. Thermal relays: A thermal relay (or overload is a temperature sensitive devicewhose

contacts open or close when the motor current exceeds a preset limit. The current flows

through a small, calibrated heating element which raises the temperature of the relay.

Thermal relays are inherent time-delay devices because the temperature cannot follow the

instantaneous changes in current.


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Figure 2.6. thermal overload relay and its parts

Many control circuits include motor overload protection devices. Thermal overload relay(OL)

protectors operate on the relationship between heat and current. As current increases, heat

increases. If an overload device is rated 10A, and the current exceeds that

rating, the OL device will operate to open the circuit because of the increased heat caused by

the current running through it.


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E. Magnetic contactors

Figure 2.7. magnetic contactors and its components

A magnetic contactor is basically a control relay designed to open and close a power circuit. It

possesses a relay coil and a magnetic plunger, which carries a set of movable contacts. When

the relay coil is energized, it attracts the magnetic plunger, causing it to rise quickly against the


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force of gravity. The movable contacts come in contact with a set of fixed contacts, thereby

closing the power circuit. In addition to the power contacts, one

or more normally open or normally closed auxiliary contacts are usually available, for control

purposes. When the relay coil is de-energized, the plunger falls, thereby opening and closing

the respective contacts. Magnetic contactors are used to control motors ranging from 0.5 hp to

several hundred horsepower. The size, dimensions, and performance of contactors are

standardized according to the rating .

Motor control circuits are an effective way to reduce cost by using smaller wire and reduced-

amperage devices to control a motor. Many smaller motors use the same size

conductors for both control and power circuits, but as the horsepower increases the conductor

size become different . Motor control circuits are often connected to lower voltages than the

motor they control to make it safer for operators and maintenance personnel. A motor control

circuit, for the most part, is simply a switch (or group of switches) and a motor. Many motors

are controlled by computerized control systems, solid-state logic controls, or programmable

logic controllers (PLCs). a single PLC can replace thousands of relays resulting in less

expensive wiring systems that offer greater flexibility in control designs.

Figure 2.9 DOL power circuit and control circuit diagram


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Figure 2.10 star delta contol circuit diagram

Figure 2.11. auto-transformer control circuitb


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Self-Check 1 Multiple chose and written questions


page:

1. One of the following is not parts of control circuit device

A/ contactor B/ overload relay C/ three phase breaker D/ all

2. The main purpose of thermal overload relay is

A/ to control the system when current increase beyond the rated values

B/it interrupts the system when temperature rises in the motor coil

C/ it regulates the system when the load increases to the system

D/ all

3. The device used to start and stop the power and the control circuit is called

A/ circuit breaker B/ timer C/ pushbutton D/ all

4. One is parts of power circuits

A, main contactor B/ pushbutton C/ thermal overload relay D/ A and C

5. What is the difference between power circuit and control circuit

A/power circuit is the line directly connected to the load B/ control circuit is operated by

low power supply C / both have different circuit diagram D/all

6. Write the device used in power circuit and control circuit separately

7. What makes difference between power circuit and control circuits ?

Answer Sheet

Name: _________________________ Date: _______________


1.______ 2_________, 3___________, 4_________, 5__________

6__________________________________________________________________________

___________________________________________

Score = ___________

Rating: ____________




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7.__________________________________________________________________________

______________________________________

Operation sheet

1

Constructing power circuit and control circuit

diagram

required materials

3-Φ Ac power supply, 3-Φ contactor ,3-Φ thermal overload relay, Screw driver/ flat or

Philips, Multimeter, Pushbutton

Single phase breaker 220v/16A, 3-Φ Ac motor

procedure


2. Read the power circuit and control circuit carefully.

3. Check all device and motor with multimeter properly

4. Construct the power circuit

5. Construct the control circuit

6. Show the constructed circuit to your trains/ instructor

7. Operate the system


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Name: _____________________________ Date: ________________




Task1. Wear PPE for safety

Task2. Read the power circuit carefully.

Task 3. Check the necessary materials used in power circuit diagram as shown below

Task4 Identify the required tools and material.

Task5 Set the continuity each devices and material

Task6Install the with good wiring

Task7Check the power on installed machine



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Information Sheet -2

Testing cable laying, joint, lamps, switches

and junction box

INTRODUCTION TO BASICS OF ELECTRICAL INSTALLATION SYSTEMS

Electrical Installation Work. specialized construction work that is performed during the

erection or reconstruction of buildings or structures intended for various purposes and that

entails the installation of electric wiring and electrical equipment

Wiring:-is a process of connecting various accessories for distribution of electrical energy from

supplier’s meter board to home appliances such as lamps, fans and other domestic appliances

is known as Electrical Wiring)

2. Good Wire Splice must be fulfill the following things

a. A wire splice is one wire connected to another wire.

b. The splice should be made so that it will conduct electricity as well as the unspliced

wire.

c. The insulation applied over the splice should also be just as good as the insulation on

the unspliced wire.

3. Splice Standards in the National Electrical Code

a. Connectors and splices must be enclosed in a junction box.

b. All splices or connections must be soldered or fastened with a solder less connector.

c. Splices with soldered connections must be wrapped with electrician's tape equivalent in

an amount to the original insulation.

3. Colors of Wires and Terminals in Structural Wiring

Colors of Wires

A. White (sometimes natural gray) colored wire must be used only for the ground wire.

B. Additional grounding conductors may be green, green with one or more yellow stripes, or a

bare wire.

C. Wiring for the "hot" wires may be any other color but it is most frequently black or red.

4) The color schemes most often used for structural wiring are:

a) Two wire circuit - white and black

https://www.electricaltechnology.org/2013/05/wiring-of-distribution-board-single.html

https://www.electricaltechnology.org/2013/05/wiring-of-distribution-board-single.html

https://www.electricaltechnology.org/2013/09/electrical-wiring.html


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b) Three wire circuit - white, black, and red

c) Four wire circuit - white, black, red, and blue

1. Splicing (Wiring techniques)

This sub topic will assist you in learning the basic skills of proper wiring techniques (splicing). It

explains the different ways to terminate and splice electrical conductors.

Conductor splices and terminal connections.Conductor splices and connections are an

essential part of any electrical circuit. When conductors join each other or connect to a load,

splices or terminals must be used. Therefore, it is important that they be properly made. The

basic requirement of any splice or connection is that it is both mechanically and electrically as

sound as the conductor or device with which it is used.

Quality workmanship and materials must be used to ensure lasting electrical contact, physical

strength, and insulation. The most common methods of making splices and connections in

electrical cables are explained in the discussion that follows.

Knife strippingA sharp knife may be used to strip the insulation from a conductor. The

procedure is much the same as for sharpening a pencil. The knife should be held at

approximately a 60º angle to the conductor.Use extreme care when cutting through the

insulation to avoid nicking or cutting the conductor. This procedure produces a taper on the cut

insulation as shown in figure 1.

Figure 1 wire striping method

Types of Wire Splices


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1. Western Union Splice it joins small, solid conductors.Figure 2 shows the steps in making a

Western Union splices.

Fig 2. Western Union splice.

Materials and Tools:-Pieces of wires, soldering lead, pocket knife, wire stripper flat nose

pliers, soldering iron, ruler, soldering paste, insulating tapegeneral purpose pliers, solder,

nipper, flux, file, brush, insulation remover, … etc.

Procedures:

1. Skin the to wire to be joined (see fig1- a)

2. Clean both wires thoroughly.

3. Cross the two bare wire ends as in fig (2.a).

4. Make a neck turn as in fig (2. b).

5. Using pliers, make a number of shoulder or twists as shown in fig (2.d).

6. Cut off the excess wire.

7. Tighten the shoulders by means of pliers.

8. Repeat operations 5, 6 and 7 with the remaining free wire winding the shoulders in the

opposite direction.

9. Solder and then insulate the splices by an insulating tape.

Note: Sometimes the western union splice with greater number of neck turns, greater

number of shoulders and no neck turns may be used.

2. Staggering Splices


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Joining small multi-conductor cables often presents a problem. Each conductor must be

spliced and taped. If the splices are directly opposite each other, the overall size of the joint

becomes large and bulky.

Figure 3 shows how a two-conductor cable is joined to a similar size cable by using a Western

Union splice and by staggering(amazing) the splices. Care should be taken to ensure that a

short wire from one side of the cable is spliced to a long wire, from the other side of the cable.

The sharp ends are then clamped firmly down on the conductor. The figure shows a Western

Union splice, but other types of splices work just as well.

Fig 3. Staggering splices.

Materials and Tools:-Four pieces of single copper or aluminum wire, each 12 cm long,

diagonal cutting pliers, pocket knife, wire stripper, flat nose pliers, soldering iron, ruler,

soldering paste, insulating tape general purpose pliers, solder, nipper, flux, …etc.

Procedures:

1. Measure about 2.5 cm from the ends of the wires to be spliced.

2. Skin the wires and prepare them as shown in fig 1-a

3. Clean the wire and prepare them in parallel (insulation to insulation

4. By means of pliers, twist the wires together as shown in fig 3.

5. Cut of the projecting wires beyond the last twist.

6. Solder the splice then cover by means of insulating tape.

3. Rattail (pigtail) Joint

A splice that is used in a junction box for connecting branch circuits is the rattail joint


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Fig4 Rattail joint.

This wiring is installed in buildings usually placed inside a conduit. Whenever branch or

multiple circuits are needed, junction boxes are used to join the conduit.

To create a rattail joint, first strip the insulation off the ends of the conductors to be joined. You

then twist the wires to form the rattail effect. This type of splice will not stand much stress.

Materials and Tools:-The pieces of single copper or aluminum wire, each 12 cm long,



Procedure:

1. Measure about 2.5 cm from the ends of the wires to be applied.

2. Remove the insulation of the measure portions as shown above in fig (1-a)

3. Clean the wire and prepare two of them

4. Cross the pieces of wire as shown in fig (4.a)

5. By means of pliers, twist the wires together as shown in fig (4-b)

6. Cut or Bend of the projecting wires beyond the last twist

7. Solder the joint to strengthen the connection.

8. Insulate the splice by means of tape or insulating cup

4. Tap (T) Joint:-Used for making a connection anywhere along the length of an other

wire. It is really one half of a western union splice.


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Figure 5. T- joint splicing

5. Flexible wire to solid wire splice (pig tail): This splice is used for joining the solid wires

used in permanent wiring together with the flexible conductors used in wiring fixtures and

appliances (two wires of different cross section).

Figure 6. flexible wire splicing


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Materials and Tools:- Wires (solid and flexible) sal-ammonic, pocket knife, wire stripper, flat

nose pliers, soldering iron, ruler, soldering paste, insulating tape general purpose pliers,

solder, nipper, flux, file, brush, insulation remover, … etc.

Procedures:

1) Measure and skin the portions of the wires as shown in fig (6-a).

2) Clean the bare wires thoroughly

3) Cross the wires as shown in fig (6-b)

4) By means of pliers, wrap the flexible wire around the solid conductor for a distance

of about 2cm

5) Bend the solid conductor parallel to the splice.

6) Cut the extra flexible wire.

7) Solder the joint to strengthen the connection.

8) Insulate the splice by means of tape .

6. Double branch splice.: used in where two branch wires, leading in opposite directions,

connected to a main wire at one point.

Figure 7. Double branch splice.:

Materials and Tools:-Pieces of wires, soldering lead, pocket knife, wire stripper,

flat nose pliers, soldering iron, ruler, soldering paste, insulating tapegeneral purpose pliers,

solder, nipper, flux, file, brush, insulationremover, … etc.

Procedures:

1) Prepare three pieces of copper single wire (12 cm long for main wire, 14 cm long for

making taps) as shown in fig (a), (b) &(c) above.

2) Skin the main wire about 4 cm at the center position as in fig (a).

3) Skin the connecting wires for about 7 cm at either ends of the wires as in fig (b)&(c).


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4) Place the branch wire across the main wire (insulation to insulation should be at an

angle of 90 degree )as in fig ( d).

5) Make five to eight shoulders on the main conductor as shown in fig (d) above. (Making

shoulders should be in the opposite direction.)

6) Cut off the excess wire.

7) Solder and then wrap the splice with insulating tape.

7. Dove-tail splice: Used for large non-flexible stranded conductors. Such splice is

mostly applied in over head transmission lines. And pump installation

Figure 8. Dove-tail splice:


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Materials and tools: Two large non-flexible stranded conductors, soldering material, .

diagonal cutting pliers, normal pliers, flat nose pliers, soldering iron, file, brush, …etc.

Procedures:

1. Measure and skin the two stranded conductors about 8 cm from 12cm long of the wire.

2. By means of binding wire tie the strands of each wires together as shown as in fig (a)

3. Straighten the strands beyond the binding wires and prepare them as in fig (b).

4. Cut off the middle strand of the two wires just at the place marked with binding wires

(refer the above fig b).

5. Over lap the strands of one wire between the other as in fig (c ).

6. Wrap the strands of one wire (about the body of the other as shown in fig d).

7. Cut excess ends of the strands and solder the joint.

8. Cover the splice with insulation tape.

2.1. Testing cable laying, joint, lamps, switches and junction box

Cable laying. cable is laying direct in ground then there shall be 75 mm bed of fine sand in

bottom before laying. Then test for insulation resistance and continuity of cable. Cover the

cable after testing 170 mm sand from base cushion.

Materials used for electrical installation

1. Switch. Is a mechanical device use to make or break electric circuit?

The types of switches are classified into four types namely:

SPST (Single Pole Single throw)-one way switch -used to control circuit from one

position

SPDT (single pole double throw)- two way switch -used to controls lamps from two

position .

DPST (double pole, single throw) gang switch used to controls different lamps from

one position.

DPDT (double pole double throw)- intermediate switch used to control lamps from three

position.


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Two three-way switches can be connected between two locations practically as;

A four-way switch is double pole double throw;

One four-way switch is required for each location in excess of two.

2. Junction box: is the place where terminals connections will be made by inserting the

wire core from either side or the wiring run and then screwing the terminal close to create a safe

electrical junction and join. A terminal junction box being used to join two sections of wiring

together.


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Figure 9. junction box and cable joints

There are different types of junction box

Fire-proof junction boxes: used to protect life and property in the case of fire


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Figure 10. different size of fire proof junction box

3. Electric lamps is a device used to converters electric energy in to light energy the

processes of tungsten wire and argon .


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Figure 11/ different lamp type


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Testing wire joints in the junction box switch and lamps

1.1. One lamp controlled by a single pole, single throw switch from one position

Procedure

1. Check or test the device used in parameters

2. Join/splice each connection property

3. Test the joint wire laid in the junction box

4. Inform to your instructor before supplying power to the circuit

N.B as we equipped with low voltage power supply we will be working on 220V, 50Hz.

Figure 12 a) lay out diagram b) wiring diagram

Figure 13. controlling one lamps form two different position


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Figure 14. controlling two lams from three different position


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page:

1. What is splicing? (2pts)

2. Writ different types of wire splicing (2pts)

3. Write briefly type of switch and their uses(2pts)

4. What is the importance of junction box? (2pts)

5. What is the purpose of lamps?(2pts)

Answer Sheet

Name: _________________________ Date: _______________


1. ______________________________________________________________________

______________________________________________________________________

__________________________________________________________

2. ______________________________________________________________________

_______________________________________________________________

3. ______________________________________________________________________

_________________________________________________

4. ______________________________________________________________________

___________________________________

5. ______________________________________________________________________

____________________

Score = ___________

Rating: ____________




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Operation sheet-1 Rattail joint. Splicing

Materials and Tools:-The pieces of single copper aor aluminum wire, each 12 cm long,



Procedure:

1. Measure about 2.5 cm from the ends of the wires to be applied.

2. Remove the insulation of the measure portions as shown above in fig (1-a)

3. Clean the wire and prepare two of them

4. Cross the pieces of wire as shown in fig (4.a)

5. By means of pliers, twist the wires together as shown in fig (4-b)

6. Cut or Bend of the projecting wires beyond the last twist

7. Solder the joint to strengthen the connection.

8. Insulate the splice by means of tape or insulating cup


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Name:

_____________________________ Date: ________________




1. Wear all safety equipment

2. Task-1 splice Western Union Splicing type

3. Task 3. Construct wire installation of controlling two lamps from three different

position



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Information Sheet -3 Selecting cable

Cables

An electrical cable also has different types, color and application as its determining factors.

Here’s a brief about cables that you need to understand to determine the correct cable for your

home.

figure 3.2 Example of cable

1. Types of Electrical Cables – There are more than 20 different types of cables available

today, designed for applications ranging from transmission to heavy industrial use. Some of

the most commonly-used ones include:.

Non-Metallic Sheathed Cable : These cables are also known as non-metallic building

wire or NM cables. They feature a flexible plastic jacket with two to four wires (TECK

cables are covered with thermoplastic insulation) and a bare wire for grounding. Special

varieties of this cable are used for underground or outdoor use, but NM-B and NM-C

non-metallic sheathed cables are the most common form of indoor residential cabling.

Underground Feeder Cable : These cables are quite similar to NM cables, but instead

of each wire being individually wrapped in thermoplastic, wires are grouped together

and embedded in the flexible material. Available in a variety of gauge sizes, UF cables

are often used for outdoor lighting and in-ground applications. Their high water-


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resistance makes them ideal for damp areas like gardens as well as open-to-air lamps,

pumps, etc.

Metallic Sheathed Cable : Also known as armored or BX cables, metal-sheathed cables

are often used to supply mains electricity or for large appliances. They feature three

plain stranded copper wires (one wire for the current, one grounding wire and one

neutral wire) that are insulated with cross-linked polyethylene, PVC bedding and a black

PVC sheathing. BX cables with steel wire sheathing are often used for outdoor

applications and high-stress installations.

Multi-Conductor Cable : This is a cable type that is commonly used in homes, since it is

simple to use and well-insulated. Multi-conductor or multi-core (MC) cables feature

more than one conductor, each of which is insulated individually. In addition, an outer

insulation layer is added for extra security. Different varieties are used in industries, like

the audio multicore ‘snake cable’ used in the music industry.

Coaxial Cable : A coaxial (sometimes heliax) cable features a tubular insulating layer

that protects an inner conductor which is further surrounded by a tubular conducting

shield, and might also feature an outer sheath for extra insulation. Called ‘coaxial’ since

the two inner shields share the same geometric axis, these cables are normally used for

carrying television signals and connecting video equipment.

Unshielded Twisted Pair Cable : Like the name suggests, this type consists of two wires

that are twisted together. The individual wires are not insulated, which makes this cable

perfect for signal transmission and video applications. Since they are more affordable

than coaxial or optical fiber cables, UTP cables are often used in telephones, security

cameras and data networks. For indoor use, UTP cables with copper wires or solid

copper cores are a popular choice, since they are flexible and can be easily bent for in-

wall installation.

Ribbon Cable : Ribbon cables are often used in computers and peripherals, with various

conducting wires that run parallel to each other on a flat plane, leading to a visual

resemblance to flat ribbons. These cables are quite flexible and can only handle low

voltage applications.

Direct-Buried Cable : Also known as DBCs, these cables are specially-designed coaxial

or bundled fiber-optic cables, which do not require any added sheathing, insulation or

piping before being buried underground. They feature a heavy metal core with many

layers of banded metal sheathing, heavy rubber coverings, shock-

absorbing gel and waterproof wrapped thread-fortified tape. High tolerance to

temperature changes, moisture and other environmental factors makes them a popular

choice for transmission or communication requirements.

Twin-Lead Cable : These are flat two-wire cables that are used for transmission

between an antenna and receiver, like TV and radio.


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Twin axial Cable : This is a variant of coaxial cables, which features two inner

conductors instead of one and is used for very-short-range high-speed signals.

Paired Cable : With two individually insulated conductors, this cable is normally used in

DC or low-frequency AC applications.

Twisted Pair : This cable is similar to paired cables, but the inner insulated wires are

twisted or intertwined.

2. Cable Color Code – Color coding of cable insulation is done to determine active, neutral

and earth conductors. The NEC has not prescribed any color for phase/active conductors.

Different countries/regions have different cable color coding, and it is essential to know what is

applicable in your region. However, active conductors cannot be green/yellow, green, yellow,

light blue or black..

Cable Size – Cable size is the gauge of individual wires within the cable, such as 14, 12, 10

etc. – again, the bigger the number, the smaller the size. The number of wires follows the wire-

gauge on a cable. So, 10/3 would indicate the presence of 3 wires of 10-gauge within the

cable. Ground wire, if present, is not indicated by this number, and is represented by the letter

‘G’.

Safety is very important, and if your installation of wires and cables is not proper, it could lead

to accidents. Before you start any electrical project that includes wiring and cabling, you need

to obtain permission from your local building inspector. Once the job is done, get the

installation inspected for compliance with local codes and regulations.

Directio

ns: Answer all the questions listed below. Use the Answer sheet provided in the

next page:

1. What is the difference between cable and wire? (2pts)

2. The cable size is determining by (2pts)

A/ cable cage B micro meter C/Viner caliper D/no one

3. From the cable color which color is used as earthing (2pts)

A/ black B/ white C/ red D/ blue

4. Cable is mostly used in (2pts)

Self-check-3 Written and multiple choose


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A/ in buildings B/ in motor installation C/ in pump installation D/ all

5. List at list three different types of cable (2pts)

Answer Sheet

Name: _________________________ Date: _______________


1. ________________________________________________________________

________________________________________________________________

________________________________________________________________

______

2. ___________

3. __________

4. _________

5. ________________________________________________________________

________________________________________________________________

____________________________________________________

Score = ___________

Rating: ____________




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Reference

www.plaisance-pratique.com › IMG › pdf › 03022009100

http://www.strancoproducts.com › downloads

http://www.cedengineering.com › userfiles

http://www. franklin-energy.com › heat_shrink_splice_instructions

http://www.te.com › DocumentDelivery › DDEControlle

https://www.clemson.edu › electronics › CInquiryLabManual

https://www.ericsson.com › local › lme-review › documents

http://www.explainthatstuff.com/amplifiers.html

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-1

https://www.elexp.com/electrical_measurements_part_3.aspx

http://www.nutsvolts.com/magazine/article/fet_principles_and_circuits_part_1

http://www.efxkits.com/blog/types-of-switches-with-applications/

https://www.androiderode.com/category/electronic-circuits/

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-7/silicon-controlled-rectifier-scr/

http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Catalog+Section%7F1654025_Sec8_D-406%7F0313%7Fpdf%7FEnglish%7FENG_CS_1654025_Sec8_D-406_0313.pdf%7F967398-000

http://www.te.com/commerce/DocumentDelivery/DDEController?Action=showdoc&DocId=Catalog+Section%7F1654025_Sec8_D-406%7F0313%7Fpdf%7FEnglish%7FENG_CS_1654025_Sec8_D-406_0313.pdf%7F967398-000

http://www.explainthatstuff.com/amplifiers.html

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-1

https://www.elexp.com/electrical_measurements_part_3.aspx

http://www.nutsvolts.com/magazine/article/fet_principles_and_circuits_part_1

http://www.efxkits.com/blog/types-of-switches-with-applications/

https://www.androiderode.com/category/electronic-circuits/

https://www.allaboutcircuits.com/textbook/semiconductors/chpt-7/silicon-controlled-rectifier-scr/

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