Industrial Electrician Handbook: Safety, Electrical Basics & More

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Industrial Electrician
Table of Contents
1.0 General safety and electrical safety...................................................................3
1.1 Lifting and handling safety...............................................................................................3
1.2 General safety of tools and equipments..........................................................................3
1.3 Electrical safety................................................................................................................6
1.4 Handling electrical fires ...................................................................................................7
1.5 First aid treatment of electrocuted person .....................................................................9
1.6 Safety permits applicable to electrical department ......................................................12
2.0 Basics of Electricity..........................................................................................15
2.1 Basic terms used in electrical technology......................................................................15
2.2 Hand tools used in electrical applications .....................................................................22
2.3 Electrical accessories used in industrial wiring..............................................................32
3.0 Electrical Circuits.............................................................................................43
3.1 Types of wires and conductors, load carrying capacity.................................................43
3.2 Wiring diagrams.............................................................................................................47
3.3 Conductors and insulators.............................................................................................55
3.4 Concepts of AC, DC, single phase and 3 phase supply...................................................57
3.5 OHMS law.......................................................................................................................63
3.6 Measurement of current, voltage & power...................................................................65
3.7 Series and parallel circuit...............................................................................................70
3.8 Fuses and MCB...............................................................................................................73
4.0 Electrical Wire.................................................................................................82
4.1 Wire gauge.....................................................................................................................82
4.2 Skinning of cables..........................................................................................................82
4.3 Types of joints................................................................................................................83
4.4 Crimping.........................................................................................................................87
4.5 Soldering ........................................................................................................................89
5.0 Wiring and testing of circuits...........................................................................91
5.1 Electrical accessories/fittings.........................................................................................91
5.2 Earthing..........................................................................................................................98
5.3 Types of faults in electrical circuits................................................................................99
5.4 Quality assurance in electrical works...........................................................................103
5.5 Energy saving concepts................................................................................................106
6.0 IE rules..........................................................................................................110
6.1 IE rules..........................................................................................................................110

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7.0 Motors..........................................................................................................117
7.1 Types of motors ...........................................................................................................117
7.2 Working principle of single phase and 3 phase induction motor................................123
7.3 Difference between squirrel case and slip ring induction motor................................124
7.5 Working principle of DOL, star delta starter and advantage.......................................126
7.6 Methods of speed control in motors...........................................................................132
7.7 Drives ...........................................................................................................................132
7.8 Tagging/identification procedures used in industries .................................................132
8.0 Transformers ................................................................................................ 135
8.1 Basic principle of transformer......................................................................................135
8.2 Types of transformers..................................................................................................135
8.3 Protective devices of transformers..............................................................................139
8.3 Various parts of transformers......................................................................................144
8.4 BDV test......................................................................................................................145
9.0 Motor Winding ............................................................................................. 146
9.1 Types of winding ..........................................................................................................146
9.2 Dismantling and re-winding an AC machine................................................................147
9.3 Insulating materials......................................................................................................150
9.4 Preparation of a winding data for a given motor ........................................................152
9.5 Testing procedure after rewinding ..............................................................................153
10.0 Transformer Winding .................................................................................. 158
10.1 Testing a transformer................................................................................................158
10.2 Measuring a enameled winding wire with wire gauge..............................................160
10.3 Steps in winding / rewinding a transformer..............................................................161
11.0 DG Set.........................................................................................................165
11.1 Function of DG set .....................................................................................................165
11.2 Various parts of DG set ..............................................................................................168
11.3 Connection and load distribution ..............................................................................168
12.0 Maintenance............................................................................................... 173
12.1 Panel cleaning methods.............................................................................................173
12.2 Major electrical breakdowns and preventive maintenance......................................174
12.3 Maintaining power ratio............................................................................................177

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1.0 General safety and electrical safety
OBJECTIVES: It is to explain trainees, what is the safety measures have to be taken during
working in field.
1.1 LIFTING AND HANDLING SAFETY
1. Switch 'off ' the motor and remove the fuse
carriers.
2. Ensure the equipment is disconnected from
supply and the base plate nuts of the motor
have been removed.
3. Make sure of the position where the
equipment is to be placed.
4. Assess whether you need any assistance to carry the equipment.
5. Check for clear route path and the location for placement. Remove obstacles, if
any.
6. Position yourself near the equipment for
lifting.
7. Lift the equipment from the floor using
the correct posture.
8. Carry the equipment to the work bench
safely, keeping the equipment close to
the body.
9. Keep the equipment carefully on the bench, and adjust its position correctly.
Assume the over-hauling work is over and the motor to be placed in its original
place.
10. Lift the equipment correctly with a firm grip.
11. Carry the equipment to the original place.
12. Lower the equipment safely with your feet apart, knees bent, back straight and
arms close to your body.
13. Place the equipment safely on the floor.
1.2 GENERAL SAFETY OF TOOLS AND EQUIPMENTS
The following procedures will prevent the human body from contact with electrical
conductors, wiring, electrical sources, etc.

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Protective measures
Insulation
Shield the electrical conductor with an insulator to prevent direct contact
Obstacles
Place obstacles to prevent any accidental
contact with the electrical conductor
Barriers or enclosures
Create barriers or enclosures that
prevent any direct contact with the
electrical conductor
Placing out of reach
This prevents accidental contact with the
electrical conductor.
Fuse
Normally, a fuse is a copper wiring with a set
current fusion value. If the current exceeds the set
fusion value, the fuse will blow and the current is
cut-off, thus preventing overloading.
A fuse must be installed on "live" wires. When
replacing a fuse, the new fuse must be of the same
current fusion value.
Circuit breakers (MCB)
Circuit breakers are based on the principle of the
electromagnetic field. The current entered may enable the
coils of the circuit breaker to magnetize. When the current
exceeds the set value (i.e., overloading), the magnetization
intensifies, switching off the circuit breaker and disconnecting
the electric source.
Earthing
Earthing provides a
low resistance way of
discharging electricity
to the ground in case
of current leakage.
This means that
during an electric
shock, the current
passes through the
"earth" wire and is prevented from entering the human body and causing injury.

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Apart from the above the following other safety tools also used in workshop
Arc Flash Protective
Clothing
Arc and Flash Fire
Resistant Rainwear
DBI Sala arc flash harnesses,
lanyards, kits, SRL's
Insulating Gloves, Kits,
Accessories
Insulating Blankets, Roll
Blankets, Aprons,
Accessories Electrical Switchboard Matting
Arc Protection Blankets
Dielectric Footwear
Hot Sticks, FRP Clamp Sticks -
Shot-gun Sticks
Static Discharge Sticks Insulated Rescue Sticks /
Hooks Grounding Equipment and Sets

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1.3 ELECTRICAL SAFETY
 Never work in wet/damp places without proper
safety.
 Do not put any metallic articles like finger rings,
bracelets or any other jewellery on your body
while working on electric supply.
 Use insulated rubber sole shoes while working.
 Do not work without any footwear.
Do not use chapels.
 The stairs used while working should be sturdy and
safe. An assistant should be working with you.
 All tools used should be
properly insulated and in good
working condition.

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 Always use insulated gloves while working on high voltage
electric supply.
 Avoid working on live parts. Switch off supply before working.
1.4 HANDLING ELECTRICAL FIRES
All fires are dangerous. They cause damage to property and loss of human lives. Electric
fires are particularly dangerous. An electrician will be required to handle electrical fires. He
must be smart, quick acting and fast in decision making to save damages of any kind.
Sources of electrical fire
The main causes of electric fire are:
1. Loose connections
The loose connection cause sparking which ultimately result in fire. The electrician
must ensure that all the connections are tight and safe.
2. Overload
If the current carries more current than what it is designed for, it may lead to fire.
The ratings of the equipment connected in a circuit should be kept in mind.
3. Use of incorrect rating of fuses
Great care should be taken in selection of fuses. Wrong selection of fuses can be
dangerous.
4. Short circuits
Short circuits occur due to failure of insulation, overheating, and use of poor quality
of cables.
Extinguishing the fire
The basic reason of growth of fire should be
understood.
The three things Fuel, Oxygen and Heat
together are responsible for fire. Whenever,
the supply of any one, or, all the 3 is stopped,
the fire will be extinguished. You should keep
this in mind, whenever the fire is to be
extinguished.
The fires are classified under categories A,B,C,
D and E for different types of fires. Ensure that

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the extinguisher, you are using is suitable for electrical fire. It will be written on the Fire
extinguisher.
Carbon dioxide, dry power and vaporizing liquid (CTC) extinguishers can be used to deal with
electric fires.
Caution:
Foam or liquid (water) extinguishers must not be used to quench electric fires. It can be
dangerous and user can get shock.
Always read and understand the operating instructions before using a Fire extinguisher.
General procedure to be adopted in the event of fire
1. Raise an alarm. Follow the method written below for giving an alarm signals when fire
breaks out.
By raising your voice and shouting Fire! Fire!
To call the attention of others running towards fire alarm/bell to actuate it other
means.
2. On receipt of the alarm signal, Stop working, Turn off all machinery and power;
Switch off fans/air circulators/exhaust fans. (Better switch off the main.)
3. If you are not involved in fighting the fire:
Leave calmly using the emergency exit. Evacuate the premises, Assemble at a safe place
along with the others, Check if anyone has gone to inform about the fire break to the
concerned authority, Close the doors and windows, but do not lock or bolt
In case of fire:
 Do not panic. Be calm.
 Switch off the electric supply immediately.
 Raise an alarm to let others know about the accident.
 Evacuate persons from the area of safety.
 Use Fire extinguishers as advised in Operating instructions.

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4. If you are involved in fire fighting:
Take instructions/give instructions for an organized way of fighting the fire.
If taking instructions:
Follow the instructions, and obey, if you can do so safely; do not risk getting trapped.
If giving instructions:
Assess the class of fire, Send for sufficient assistance and inform the fire brigade, Locate
locally available suitable means to put out the fire. Judge the magnitude of the fire;
ensure emergency exit paths are clear of obstructions and then attempt to evacuate
(Remove explosive materials, substances that can serve as a ready fuel for fire within
the vicinity of the fire break.). Fight out the fire with assistance to put it out, by naming
the person responsible for each activity.
5. Report the fire accident and the measures taken to put out the fire, to the authorities
concerned.
Reporting all fires however small helps in the investigation of the cause of the fire. It
helps to prevent the same kind of accident occurring again.
1.5 FIRST AID TREATMENT OF ELECTROCUTED PERSON
Electric shock:
The severity of an electric shock will depend on the level of the current which passes
through the body and the length of time of the contact.
Other factors that contribute to the severity of shock are:
 age of the person
 not wearing insulating foot weal or wearing wet footwear
 weather condition
 Mains voltage etc.
Effects of electric shock:
The effect of current at very low levels may only be an
unpleasant tingling sensation, but this in itself may be
sufficient to cause one to lose his balance and fall.
At higher levels of current, the person receiving the shock
may be thrown off his feet and will experience severe
pain, and possibly minor burns at the point of contact.
An excessive level of current flow, the muscles may contract and the person unable to release his
grip on the conductor. He may lose consciousness and the muscles of the heart may contract
spasmodically (fibrillation). This may be fatal.
Electric shock can also cause burning of the skin at the point of contact.

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Treatment of electric shock
Prompt treatment is essential.
If assistance is close at hand, send for medical aid, then carry on with emergency treatment.
If you are alone, proceed with treatment at once.
Switch off the current, if this can be done without undue delay. Otherwise, remove the victim
from contact with the live conductor, using dry non-conducting materials such as a wooden
bar, rope, a scarf, the victim's coattails, any dry article of clothing, a belt, rolled-up
newspaper, non-metallic hose, PVC tubing, bakelised paper, tube etc.
Avoid direct contact with the victim. Wrap your hands in dry material if rubber gloves are not
available.
Electrical burns:
A person receiving an electric shock
may also sustain burns when the
current passes through his body. Do
not waste time by applying first aid
to the burns until breathing has
been restored and the patient can breathe normally - unaided.
Burns and scalds:
Burns are very painful. If a large area of the body is burnt, give no treatment, except to exclude
the air, e.g. covering with water, clean paper, or a clean shirt. This relieves the pain.
Severe bleeding:
Any wound which is bleeding profusely, especially in the wrist, hand or fingers must be considered
serious and must receive professional attention. As an immediate first aid measure, pressure
on the wound itself is too best means of stopping the bleeding and avoiding infection.
Immediate action:
Always in cases of severe bleeding:
 make the patient lie down and rest
 if possible, raise the injured part above the level of
the body (Fig)
 apply pressure to the wound
 Summon assistance.

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Control severe bleeding:
Squeeze together the sides of the wound. Apply pressure as long as it is necessary to stop
the bleeding. When the bleeding has stopped, put a dressing over the wound, and cover it with
a pad of soft material. (Fig)
For an abdominal stab wound, such as may be caused by
falling on a sharp tool, keeps the patient bending over
the wound to stop internal bleeding.
Large wound:
Apply a clean pad (preferably an individual dressing)
and bandage firmly in place.
If bleeding is very severe apply more than one
dressing. (Fig)
Follow the right methods of artificial respiration.
 Remove the victim from contact with the live equipment.
 Tight clothing which may interfere with the victim's breathing must be loosened.
 Remove any foreign materials or false teeth from his mouth, and keep the mouth
open.
 Do not delay artificial respiration for loosening clothes or even if the mouth is
closed tightly
 Nelson's arm-lift back pressure method must not be used in case there are injuries
to the chest and belly.
 Place the victim prone (that is, face
down) with his arms folded with the
palms one over the other and the head
resting on his cheek over the palms.
Kneel on one or both knees near the
victim's hand. Place your hands on the
victim's back beyond the line of the
armpits, with your fingers spread
outwards and downwards, thumbs just
touching each other as in Fig.
 Gently rock forward keeping the arms straight until they are nearly vertical, and
thus steadily pressing the victim's back as in Fig to force the air out of the victim's
lungs.

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 Synchronizing the above movement rock
backwards, slide your hands downwards
along the victim's arms and grasp his
upper arm just above the elbows as shown
in Fig. Continue to rock backwards.
 As you rock back, gently raise and pull
the victim's arms towards you as in Fig
until you feel tension in his shoulders.
To complete the cycle, lower the
victim's arms and move your hands up
to the initial position.
Other steps
1. Send for a doctor immediately.
2. Continue artificial respirations till the victim begins to breathe naturally. Please
note in some cases it may take hours.
3. Keep the victim warm with a blanket, wrapped up hot water bottles or warm
bricks; stimulate circulation by stroking the insides of the arms and legs towards
the heart.
4. When the victim revives, keep him lying down and do not let him exert himself.
5. Do not give him any stimulant until he is fully
1.6 SAFETY PERMITS APPLICABLE TO ELECTRICAL DEPARTMENT
 Only qualified persons should do electrical work.
 Keep the workshop floor clean and tools in good condition.
 Do not work on live circuits; if unavoidable, use rubber gloves rubber mats, etc.
 Use wooden or PVC insulated handle screwdrivers when working on electrical
circuits.
 Do not touch bare conductors
 When soldering, arrange the hot soldering irons in their stand. Never lay switched
'ON' or heated soldering iron on a bench or table as it may cause a fire to break out.

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 Use only correct capacity fuses in the circuit. If the capacity is less it will blow out
when the load is connected. If the capacity is large, it gives no protection and
allows excess current to flow and endangers men and machines, resulting in loss
of money.
 Replace or remove fuses only after switching off the circuit switches.
 Use extension cords with lamp guards to protect lamps against breakage and to
avoid combustible material coming in contact with hot bulbs. Use accessories like
sockets, plugs and switches and appliances only when they are in good condition and
be sure they have the mark of BIS marked accessories is explained under
standardization.
 Never extend electrical circuits by using temporary wiring.
 Stand on a wooden stool or an insulated ladder while repairing live electrical circuits/
appliances or replacing fused bulbs. In all the cases, it is always good to open the
main switch and make the circuit dead.
 Stand on rubber mats while working/operating switch panels, control gears etc.
 Position the ladder, on firm ground.
 While using a ladder, ask the helper to hold the ladder against any possible slipping.
 Always use safety belts while working on poles or high rise points.
 Never place your hands on any moving part of rotating machine and never work
around moving shafts or pulleys of motor or generator with loose shirt sleeves or
dangling neck ties.
 Only after identifying the procedure of operation, operate any machine or apparatus.
 Run cables or cords through wooden partitions or floor after inserting insulating
porcelain tubes.
 Connections in the electrical apparatus should be tight. Loosely connected cables
will heat up and end in fire hazards.
 Use always earth connection for all electrical appliances along with 3-pin sockets
and plugs.
 While working on dead circuits remove the fuse grips; keep them under safe custody
and also display 'Men on line' board on the switchboard.
 Do not meddle with interlocks of machines/switch gears.
 Do not connect earthing to the water pipe lines.
 Do not use water on electrical equipment.
 Discharge static voltage in HV lines/equipment and capacitors before working on
them.

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ASSIGNMENTS
1. What Safety precaution would you observe to avoid electrical accidents?
2. What Safety points would you observe during shifting?
3. What is Artificial respiration?
4. What you do during event of fire?
5. Safety of wire depends upon what?
6. What is the role of fuse?
7. What is MCB?
8. MCB works on which principle?
9. Earthing is necessary, why?
10. What is prompt treatment?
11. What are fire extinguishers?
12. How heavy equipment shifted from one place to another place?
13. How artificial respiration done for a person who is getting shock?

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2.0 Basics of Electricity
OBJECTIVES: This is to understand and remember the basics of electricity.
2.1 BASIC TERMS USED IN ELECTRICAL TECHNOLOGY
The terms you are required to know are: Volt, ampere (amp), watt, ohm, resistance,
potential difference, rectifier, rheostat, conductor, ground, circuit, and short circuit. The
others in here are good to know.
Electron
Electrons are tiny negatively charged particles that orbit the
positively charged nucleus of atoms. Electrons are so small that
they only account for a very small portion of the overall mass of the
atom. To get a better idea of what's going on; see the Bohr model
for Aluminum to the right. The number of protons in an atom (in
this case, 13) indicates the atomic number of an atom.
The interaction of electrons between atoms allows the formation of chemical bonds.
Current flow through a circuit is these electrons jumping from atom to atom at about the
speed of light.
When an atom looses or gains an electron, the atom no longer has a neutral charge
becomes ionized. Here is an example
Potential Difference
The difference in electrical potential, or voltage, from one point in a circuit to another. The
voltage rating on a battery describes the potential difference between its terminals.
Regardless of the potential in circuit, there can be no current flow until the terminals are
connected, or there is enough energy to overcome a barrier (like air) and electrons are
allowed to flow from one terminal to another. So, if you have a 10,000 volt battery, and it's
not connected to anything, there will be no current flow-- but as soon as you touch both
terminals you'll get a nasty surprise.

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Volt (V)
Voltage a unit of measure is the driving force, or potential difference behind electron flow,
and hence the force behind the flow of current in an electrical circuit.
 Voltage is a measure of the energy carried by the charge.
Strictly: voltage is the "energy per unit charge".
 The proper name for voltage is potential difference
or P.D. for short, but this term is rarely used in
electronics.
 Voltage is supplied by the battery (or power
supply).
 Voltage is used up in components, but not in wires.
 We say voltage across a component.
 Voltage is measured in volts, V.
 Voltage is measured with a voltmeter, connected in parallel.
 The symbol V is used for voltage in equations.
Resistance
The resistance of a circuit to the flow of electrons, or current flow. Everything has some
resistance associated with it, even metal wires. Some of these resistances are so small that
we will ignore them in most cases. Heat changes the resistance of all materials. Some
materials will increase their resistance as they get hotter, others will decrease their
resistance. This property of materials can be used to make electronic circuits that can
measure heat.
Ohm (Ω)
The unit of measure for a circuit’s resistance to current flow.
Resistor
Resistors have resistance, and their primary function is to add resistance to a circuit. The
electrical symbol for a resistor is . Below is a picture of what some resistors look
like. The large white one is a power resistor. Power resistors can handle a lot of current flow
without burning up. The color bands indicate the resistance; the
color of the body indicates the type of resistor (carbon, wire, and so
on). The tan resistors are carbon resistors.
Current
The flow of electrons in a circuit, measured in Amps.
Current, I
 Current is the rate of flow of charge.

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 Current is not used up, what flows into a component must flow out.
 We say current through a component.
 Current is measured in amps (amperes), A.
 Current is measured with an ammeter, connected in series.
To connect in series you must break the circuit and put the ammeter across the gap,
as shown in the diagram.
 The symbol I is used for current in equations.
Direct Current (DC)
Direct current sources never have current flowing in the opposite direction, that is, the
positive and negative sides never reverse. A battery only produces direct current when
connected to a circuit (the circuit can change the DC into AC).
Alternating Current (AC)
Alternating current means the current flow goes one
way and then reverses its direction at regular time
interval. This happens because one terminal is
negative and the other is positive for a while, then
they switch from being negative to positive and from
positive to negative. In India frequency of AC is 50 HZ.
A person that has been shocked for by AC should be
watched for a few hours to make sure he doesn't have
a heart attack.
Battery
Batteries convert chemical energy into electrical energy.
Multiple battery cells can be connected in series to
increase the voltage of the circuit. All batteries have some
internal resistance, which means some batteries are better
at high current flows than others.
The plus sign isn't always there. The longer end indicates
the positive terminal, and the smaller one is the negative
terminal. Some electrical drawings have several of these
battery cell symbols staked on each other. This means it's a
battery pack, or just a battery.
Current Flow and Electron Flow
Both terms essentially mean the same thing when talking about an electrical circuit:
electrons moving from one place in a circuit to another. The direction of current flow was

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determined by Benjamin Franklin, who said that current flows from the positive to negative.
Well, he had a 50% chance of getting that right and just missed it.
Electrons really flow from the negative terminal to
the positive terminal. When we talk about Current
Flow we assume that current flows from positive
to negative. When we talk about Electron Flow, we
assume that current flows from negative to
positive (which is really the case). When working
with circuits, it makes little difference if you use
electron or current flow. Since most books use current flow, rather than electron flow
(which is a newer term), that is what we will be using. When we start talking about what
happens inside of semiconductors (transistors, diodes, etc), we have to talk about electron
flow within that component to understand what is going on inside.
But Electron Flow is what's really happening in a circuit on a subatomic level. When we talk
about AC, the direction of current changes constantly, so we just pick a direction and sick
with it when performing circuit analysis.
Conductor
A material in which current is able to flow through easily. Most metals make good
conductors, some better than others, silver being the best in normal conditions. Super-
conductors have nearly no resistance to current flow, but they often have to be super-
cooled to work and are very expensive.
Semiconductor
These materials can either be good conductors or good insulators, or somewhere in
between, based on certain conditions. They are used in diodes, transistors, and other
electrical components. They are very useful and are the reason why we have the computers
we have today. The most common base material used in semiconductors is Silicon (Si), the
second is Germanium (Ge). Germanium semiconductor components take away less of the
electron's energy than Silicon, but are more expensive. Silicon is refined from beach sand.
Insulator a material that does not conduct current very well. It is the exact opposite of a
conductor. The rubber around wires is an insulator. Glass is also used as an insulator.
Watt (W)
The measurement of power in a circuit, as determined by multiplying volts times amps: P=V
x I
A Kilowatt is 1,000 watts. A Watt-Hour is the number of watts used over an hour. You can
think of Watt as measuring the speed you're using power, like MPH (miles per hour), and a
Watt-hour as the distance you've actually traveled over that time. Using Ohms Law, by

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substituting V for I x R we get P=R x I2
. We will use this equation when talking about why the
power companies step up line voltage to insane values in transmission lines, and later step it
back down to household values.
Short Circuit
Current wants to take the path of least resistance. If there is a path of very low resistance,
current will want to flow that direction more than any other. When there is a path of very
low resistance back to the power source (which isn't supposed to be there), we call this a
short circuit. A short circuit can cause a fire.
Fuse
A fuse is a device that, if a current level is exceeded,
the wire, or substance inside of the fuse, will heat
up and then melt, breaking the electrical
connection. There are fast and slow blow fuses. Fast
blow fuses are used to protect circuits from short
circuit conditions. Slow blow fuses don't blow right
away when they have reached their current rating.
Slow blow fuses are used with motors and other
components that have high starting currents.
Circuit Breaker
A Circuit Breaker provides overload protection. They are slower
acting than a fuse. Circuit breakers are electro-mechanical devices
(which mean they are part electrical and part mechanical) which
will break a circuit if too much current is flowing through a circuit
for too long.
Rheostat/Potentiometer
A Rheostat is similar to a resistor, except that the resistance of
the component can be changed by turning a knob or moving a
slider (slide-type rheostats are used on sound mixing boards).
That is why the electrical symbol looks like a resistor with an
arrow through it. That line means that it can be adjusted. You'll
see something similar on other devices that can be adjusted by
a knob, such as capacitors and inductors.
Generator
A device that generates electron flow through moving a conductor through a magnetic field.
The amount of voltage induced in the generator coil is directly proportional to the strength
of the magnetic field, and the speed at which the magnetic field is changing or moving
through the conductor.

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Transformer
Transformers are able to step up, or step down AC voltages
through magnetic field interactions. They are also able to isolate an
AC circuit form other AC circuits. AC current causes the magnetic
field to continually grow, decrease, and then increase over and
over again. This produces a moving magnetic field Just like what's needed to make a
generator work. To the right is a diagram of a transformer. To the left is the electrical
symbol for a transformer.
Rectifier
A device that converts AC into DC. Diodes are used to rectify a AC into DC because they
allow current to flow only in one direction. In order to produce a clean DC output, filters
have to be used. Usually capacitors are used in these filters. Another method that is used to
convert AC to DC is the use of a motor-generator set. AC motor is used to spin a DC
generator. It's not as efficient as using a rectifier, but they are cheaper for large current
applications and are used on some older elevator systems.
Ground
Ground is considered at zero potential. There are two
types of grounds: a circuit or chase ground, and an
earth ground. An earth ground means that the ground
is somehow physically connected to the ground you’re
standing on. A circuit or chase ground just means that
there is a wire or connection that is connected to the
case that the circuit is housed in. The earth ground is
often connected to the metal case of the machine.
Electricity takes the path of least resistance, so, if there is a good earth ground to a metal
case, electricity would rather flow through the grounding wire instead of you. The grounding
wire in a house is either green or bare copper.
If you don't have three prong outlets in your house, you need to have a licensed electrician
come out and rewire your house. He'll also put in a device called a GFCI, or Ground Fault
Interrupter. GFCI's will break the circuit if there is a ground fault-- like what would happen if
you drop something electrical in a tub.

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Inductor
An inductor is a coil of wire, any coil of wire is actually an inductor. Inductors, by
themselves, tend to resist a change in current flow. They store energy in the magnetic field
produced by current moving through a conductor. When current flow begins to slow, the
magnetic field begins to collapse, and thus induces a voltage in the coil that increases
current flow. There are a few applications for inductors, such as used in filters. Motors are
also inductors, and, next to transformers, are the largest inductors in an electrical circuit.
Cutting off power to these circuits can cause a large voltage spike which is called an
"inductive kick." Capacitors are used to suppress this inductive kick by counteracting the
effect of the inductor.
Capacitor
A device that resists changes in voltage. It stores electrons between metal plates and an
insulator. They are used in filters, and power supplies to maintain voltage during current
surges. They also cancel out the effect of inductors in AC circuits and suppress the "inductive
kick" in both AC and DC circuits.
Capacitors come in many shapes and sizes.
Diode
Diodes were the first semiconductor component developed. They only allow current to flow
in one direction. They find uses in many places, and are the main components of rectifiers. A
minimum voltage is required in order for a diode to pass current through it. Here is what
they look like:
Lamp/Light Bulb
Basic incandescent light. It produces light by heating up a special wire, called a filament,
which then glows. The element that is commonly used in light bulbs is Tungsten, because it
begins to glow well before it reaches its melting point. The mantels in gas lanterns now use
tungsten for the same reason (they used to use Thorium, which is radioactive, but stopped
in the 1980s).
LED (Light Emitting Diode)
LEDs are special diodes that, when current passes through them, they will light up. They use
far less power than a lamp, and last far longer. The little arrows are supposed to show
photons, or light, being emitted.
Resistors are often needed with LEDs to lower the current flow through the LED to a safe
value (dependent on the LED, but around 10-30 milliamps is usually good). Different color
LEDs require different minimum voltages to turn on.

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2.2 HAND TOOLS USED IN ELECTRICAL APPLICATIONS
There are innumerable types of hand tools used for different types of work. Some of the
basic tools which are a must for mechanic electronics are dealing in:
 screwdrivers
 pliers, and
 Tweezers.
Screwdrivers
A screwdriver is a tool used to tighten or loosen screws. A simple screwdriver and its parts
are shown in Fig.
When a screwdriver is used to tighten or loosen screws. The blade axis of a screwdriver
must be linked up with that of the screw axis as shown in Fig 2.
Length of blade L and Length of tip W
Normally there is no relationship between the length of the blade and the width of the tip of
a screwdriver. A screwdriver with a 6 mm wide tip can have blade lengths ranging from 25
to 250 mm. It can also have various forms of handles as shown in Fig 10.

23 | P a g e
There are, however, screwdrivers which are made to an industrial specification such as DIN,
ISI etc. These screw-drivers have fixed dimensions and for each size of screwdriver the width
of its tip and the length of its blade are specified as shown in Fig 11.
Fig 12 shows a Phillips cross-type screwdriver tip. It is used to tighten and loosen screws
with a Phillips cross type recess.
Fig 13 shows a POZIDRIV CROSS TYPE screw driver tip. It is an improved type of a cross type
tip. It has straight wings compared to the slightly tapered wings of the Phillips type tip. The
straight wings keep the tip in the recess when turning force is applied to the screwdriver.
Straight wings and Tapered wings
The above cross type screwdriver tips are available in five standard sizes, numbers 0, 1, 2, 3
and 4 as shown in Fig 14. These five sizes of tips are used for all screws with cross type
recesses from M2 to M12.7.
Screwdrivers with cross type tips are also available with short blades ranging in lengths from
25 to 40 mm and with various forms of handles as shown in Fig 15. To show the difference
between the screwdrivers with short and long blades a '0' is placed in front of the tip
number of the short version.
A few examples of other types of
screwdriver tips for screw heads with

24 | P a g e
various forms of recesses are shown in Fig 16.
1. Hexagonal socket head
2. Spine socket head
3. Clutch socket head
4. Slab socket head
Never use the wrong type or size of a screwdriver as this will damage the recess of a screw
head. If in doubt, ask your instructor/ask an experienced person to tell you which tip should
be used.
Instrument screwdrivers
Fig 17 shows an INSTRUMENT SCREWDRIVER. It is used to
turn very small screws as used in instruments, watches
and clocks. It has a rotating head which is held by the
forefinger, while the thumb and the middle finger are
used to turn the screwdriver.
Instrument screwdrivers are available in sets comprising 5
to 8 screwdrivers with the dimensions as given in the
Table.
Large screws can be turned easily by using screwdriver bits that fit into a carpenter brace.
Such bits are available in different types and sizes of tips.
Fig 18 shows a screwdriver with INTERCHANGEABLE TIPS. Such screwdrivers are available in
sets comprising one handle with a universal fitting and an assortment of tips in various
shapes and sizes.
Impact screwdrivers
Fig 19 shows an IMPACT SCREWDRIVER. It is used to
tighten screws or loosen very tight screws. When the
end of its handle is struck by a hammer, a powerful
turning force is applied to the screw.
Impact screwdrivers consist of a metal handle which

25 | P a g e
can be used with a variety of exchangeable tips to suit different screw heads as shown in Fig
20.
Fig -20
Screwdrivers for electrical work have fully insulated plastic or rubber handles. The handles
are cast around the blades. Screwdrivers for heavy mechanical work often have blades
which extend through the handle as shown in Fig 21 b. Such screwdrivers can be struck by a
hammer in certain circumstances.
Screwdrivers for electrical work often have
insulated blades in the form of plastic sleeves
which are fitted up to the tip of the blades as
shown in Fig 22.
Special types of screwdrivers
Fig 23 shows a flat screwdriver tip with two
prongs. It is used with screws having two
rectangular recesses or with slotted nuts. It is
available in various sizes suitable for screws and
nuts ranging from M3 to M12.
Fig 24 shows a flat screwdriver tip with two round
pins. It is used with screws and nuts having two round
recesses which accommodate the pins. It is also avail-
able in a number of sizes for screws and nuts ranging
from M3 to M12.

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Using a screwdriver
The general procedure for using a screwdriver is given below.
 Select a suitable screwdriver having the required blade length, width of tip and
thickness of tip.
 Check that the tip of the screwdriver is flat and square.
Worn out tips tend to slip off while turning and may cause injury.
 Make sure your hands and the screwdriver handle are dry and free from grease.
 Hold the screwdriver with the axis in line with the axis of the screw.
 Guide the blade with one hand as shown in Fig 23. Set the tip of the screwdriver in
the screw slot.
 Be sure of the direction in which the screwdriver is to be twisted. Twist the handle
gently and steadily.
Do not apply too much pressure in the axial direction of the screw. This may damage the
screw threads.
Never try to use a screwdriver as a lever; this could break the tip or bend the blade and make
the screwdriver unusable.
Pliers
Pliers are tools which are used for:
 holding, gripping, pulling and turning small
parts and components,
 shaping and bending light sheet metal
parts,
 Forming, bending, twisting and cutting
small diameter wires.
Pliers consist basically of a pair of LEGS which are
joined by a PIVOT as shown in Fig 25. Each leg
consists of a long HANDLE and a short JAW.
If the legs of the pliers are crossed at the pivot, the
jaws will CLOSE when pressure is applied to the
handles as shown in Fig 25b. In some pliers the
jaws will close when pressure is applied to the handles as shown in Fig 25c. Pliers have
SERRATED or PLAIN JAWS as shown in Fig 26. Surrogated jaws offer a better grip on the
work piece. Serrated jaws might, however, damage the surface of the work piece. In this
case protection sleeves or pliers with non-serrated jaws as shown in Fig 26b should be used.

27 | P a g e
Pliers are made from high quality steel. In many
cases pliers are CHROMIUM PLATED to protect
them against rust. In climates with a high degree
of humidity it is advisable to use such pliers as
they will last longer and need less maintenance.
To keep
pliers in good
working condition, they should be kept clean, the metal
parts should be wiped with an oily piece of cloth and,
from time to time, a drop of oil should be applied to the
pivots and joints.
Diagonal cutter pliers
Fig 27 shows diagonal cutting pliers or side
cutting pliers.
They are used for cutting small diameter
wires and cables, especially when they are
close to terminals..
End cutting pliers
Fig 31 shows END-CUTTING PLIERS or END
NIPPERS and their applications.
They are used to cut small diameter wires,
pins, nails and to remove nails from wood.
End cutting pliers are made in the following
overall lengths:
130, 160, 180, 200, 210 and 240 mm.
Flat nose pliers
Fig 32 shows a FLAT NOSE PLIERS and its
applications.
They are used to form and shape wires and small
pieces of metal.

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They are also used for other operations such
as removing the metal sheath from cables, or
gripping and holding small parts. Flat nose
pliers are made in the following overall
lengths: 100, 120, 140, 160, 180 and 200 mm.
Round nose pliers
Fig 33 shows ROUND NOSE PLIERS and its
applications.
They are used to form curves in wires and
light metal strips. The conical shape of the
jaws makes it possible to form curves and
circles of various dimensions. They are also
used to form eyelets in wires to fit terminal
screws, and to hold small parts. Round nose
pliers are made to the following overall
lengths:
100, 120, 140, 160, 180 and 200 mm
Long nose pliers
Fig 34 shows a LONG NOSE PLIERS and its applications. These pliers are made with straight
and curved jaws.
They are used to hold small parts, especially in confined areas. They are also used to adjust
fine wires, contacts and other parts. Long nose pliers are made with many differently

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shaped jaws as shown in Fig 11. Long nose pliers are
available in the following overall lengths: 160, 180, 200
and 220 mm.
Combination pliers
Fig 36 shows a COMBINATION PLIERS and its application.
A number of operations can be performed with these
pliers. The FLAT GRIP can be used to grip and hold parts
and components and to twist wires.
Circlip pliers for external Circlip
Fig 37 shows a CIRCLIP PLIER for EXTERNAL
CIRCLIPS. The prongs of the jaws are inserted into
the holes of the Circlip. By applying pressure to
the handles of the pliers, the jaws will expand the
Circlip which can then be removed or moved onto
the work piece.
These pliers are available with straight and curved jaws in the following dimensions.
Circlip pliers for internal Circlip
Fig 38 shows ClRCLIP PLIERS for INTERNAL CIRCLIPS. By applying pressure to the handles of
the pliers, the jaws will compress the Circlip which can then be removed from the work
piece.
These pliers are also available with straight and curved jaws in the following dimensions.

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Pliers used by electrician
A number of pliers, especially diagonal
cutting pliers, combination pliers, flat
nose pliers, round nose pliers and long
nose pliers, are frequently used by
electricians.
As an additional safeguard against
electric shock, these pliers are available
with insulated handles made of high
quality rubber or plastic as shown in Fig
39.
Before you work with electrical
installations or electrical appliances, they
have to be disconnected from the electrical supply. Working with live parts of an electrical
installation or appliance can INJURE or KILL you, and it might seriously damage the
Installation and equipment.
Tweezers
Tweezers are used to hold light weight and very small components and very thin
wires/strands. Tweezers are classified according to the shape of the tip and are specified by
their length and shape. Fig 40 shows different types of tweezers.
The thin structure of the tweezers permits easy access to places where fingers cannot reach.
Tweezers are very useful during soldering of wires, components and placing of small screws
in interior places.

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Types of screws and screw heads
Different types of screws used in various electrical applications and sizes are given below

32 | P a g e
2.3 ELECTRICAL ACCESSORIES USED IN INDUSTRIAL WIRING
Switch board
An electric switchboard is a device that directs electricity from one source to another. It is
an assembly of panels, each of which contains switches that allow electricity to be
redirected.
Switch Board Distribution Board
Distribution board
A distribution board (or panel board) is a component of an electricity supply system which
divides an electrical power feed into subsidiary circuits, while providing a protective fuse or
circuit breaker for each circuit, in a common enclosure. Normally, a main switch, and in
recent boards, one or more Residual-current devices (RCD) or Residual Current Breakers
with Over current protection (RCBO), will also be incorporated
Circuit breaker
A circuit breaker is an automatically operated electrical switch designed to protect an
electrical circuit from damage caused by overload or
short circuit. Its basic function is to detect a fault
condition and, by interrupting continuity, to
immediately discontinue electrical flow. 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. Circuit
breakers are made in varying sizes, from small devices that protect
an individual household appliance up to large switchgear designed to
protect high voltage circuits feeding an entire city.
Electric meter
An electricity meter or energy meter is a device that measures the
amount of electric energy consumed by a residence, business, or an
electrically powered device.

33 | P a g e
Electricity meters are typically calibrated in billing units, the most common one being the
kilowatt
Measuring instruments
Meter
A meter is any device built to accurately detect and display an electrical quantity in a form
readable by a human being. Usually this "readable form" is visual: motion of a pointer on a
scale, a series of lights arranged to form a "bargraph," or some sort of display composed of
numerical figures. In the analysis and testing of circuits, there are meters designed to
accurately measure the basic quantities of voltage, current, and resistance.
Different types of meter
Ammeter
A meter designed to measure electrical current is popularly called an "ammeter" because
the unit of measurement is "amps."
In ammeter designs, external resistors added to extend the usable range of the movement
are connected in parallel with the movement rather than in series as is the case for
voltmeters. This is because we want to divide the measured current, not the measured
voltage, going to the movement, and because current divider circuits are always formed by
parallel resistances.
Voltmeter
As was stated earlier, most meter movements are sensitive devices. Some D'Arsonval
movements have full-scale deflection current ratings as little as 50 µA, with an (internal)
wire resistance of less than
1000 Ω. This makes for a
voltmeter with a full-scale
rating of only 50 mill volts
(50 µA X 1000 Ω)! In order
to build voltmeters with
practical (higher voltage)
scales from such sensitive
movements, we need to

34 | P a g e
find some way to reduce the measured quantity of voltage down to a level the movement
can handle.
Wattmeter
Power in an electric circuit is the product (multiplication) of
voltage and current, so any meter designed to measure
power must account for both of these variables.
Three-Phase Wattmeter
Total power in a 3f circuit is the
sum of the powers of the separate phases. The total power
could be measured by
placing a wattmeter in
each phase (Figure);
however, this method is
not feasible since it is
often impossible to break
into the phases of a delta
load. It also may not be
feasible for the Y load, since the neutral point to which the wattmeters must be connected
is not always accessible. Normally, only two wattmeters are used in making 3f power
measurements.
Ohmmeter
An ohmmeter is an electrical instrument that measures electrical resistance, the opposition
to an electric current. Micro-ohmmeters (micrometer or micro ohmmeter) make low
resistance measurements. Meg ohmmeters (aka mega ohmmeter or in the case of a
trademarked device Megger) measure large values of resistance. The unit of measurement
for resistance is ohms (Ω).
Power factor meter
The power factor of an AC electrical power system
is defined as the ratio of the real power flowing to
the load to the apparent power in the circuit, and is
a dimensionless number between 0 and 1. Real
power is the capacity of the circuit for performing
work in a particular time. Apparent power is the
product of the current and voltage of the circuit. .

35 | P a g e
Linear loads with low power factor (such as induction
motors) can be corrected with a passive network of
capacitors or inductors. Non-linear loads, such as
rectifiers, distort the current drawn from the system. In
such cases, active or passive power factor correction
may be used to counteract the distortion and raise the
power factor. The devices for correction of the power
factor may be at a central substation, spread out over a distribution system, or built into
power-consuming equipment.
High voltage ohmmeters (Megger)
 It is a test of the insulation properties of such
things as electric wiring, motor windings and
high power antenna mounts. We use a
"megger" or "meg out" electrical wiring and
equipment to see if it is shorted to ground in
any way. The megger uses much higher
voltages to check resistance than a normal
Volt-ohm meter.
Resistance is measured between the Line and Earth
terminals, where current will travel through coil 1. The "Guard" terminal is provided for
special testing situations where one resistance must be isolated from another. Take for
instance this scenario where the insulation resistance is to be tested in a two-wire cable:
To measure insulation resistance from a conductor to the outside of the cable, we need to
connect the "Line" lead of the megger to one of the conductors and connect the "Earth"
lead of the megger to a wire wrapped around the sheath of the cable:

36 | P a g e
In this configuration the megger should read the resistance between one conductor and the
outside sheath. Or will it? If we draw a schematic diagram showing all insulation resistances
as resistor symbols,
Multimeter
The multimeter is a portable single instrument capable of measuring various electrical
values including voltage, resistance, and current. The volt-ohm-milliammeter (VOM) is the
most commonly used multimeter. The typical VOM has a meter movement with a full scale
current of 50 µA, or a sensitivity of 20 KW/V, when used as a DC voltmeter. A single meter
movement is used to measure current, AC and DC voltage, and resistance. Range switches
are usually provided for scale selection (e.g., 0-1V, 0-10V, etc).Seeing as how a common
meter movement can be made to function as a voltmeter, ammeter, or ohmmeter simply by
connecting it to different external resistor networks, it should make sense that a multi-
purpose meter ("multimeter") could be designed in one unit with the appropriate switches)
and resistors.
This particular brand and model of digital meter has a rotary selector switch and four jacks
into which test leads can be plugged. Two leads -- one red and one black -- are shown
plugged into the meter. A close examination of this meter will reveal one "common" jack for
the black test lead and three others for the red test lead. The jack into which the red lead is
shown inserted is labeled for voltage and resistance measurement, while the other two
jacks are labeled for current (A, mA, and µA) measurement. This is a wise design feature of
the multimeter, requiring the user to move a test lead plug from one jack to another in
order to switch from the voltage measurement to the current measurement function. It
would be hazardous to have the meter set in current measurement mode while connected
across a significant source of voltage because of the low input resistance, and making it
necessary to move a test lead plug rather than just flipped the selector switch to a different
position helps ensure that the meter doesn't get set to measure current unintentionally.

37 | P a g e
volt/ammeter:
If an ohmmeter function is desired in this multimeter design, it may be substituted for one of
the three voltage ranges as such: With all three fundamental functions available, this
multimeter may also be known as a volt-ohm-milliammeter.
Neon Tester
A handy inexpensive item to add to a tool box is the one dollar neon tester. It is useful to
identify polarity in DC and identify
the ungrounded conductor in AC
circuits. For DC there is a polarity
indicator. In AC simply hold one end
of the tester between your fingers
and touch the other end of the tester
to the conductor to be measured. A
slight glow will be present if you are
on the ungrounded conductor. The only caution for that method was that both lamps had to
be identical or at high voltage the higher resistance could explode. Not good. Sometimes the
tester is made to be part of a screw driver. Sometimes it is made like a stick man with no
arms.
Another type of neon tester is the receptacle outlet tester, a very useful tool for every
electrician. This item, when plugged into an outlet, will give you detailed indication of how
the receptacle is wired. Be sure to hold on to the instructions. The diagrams of conditions on
the unit will wear off over time. Perhaps that is the time to get a new one. Anyway, it is also
useful before plugging in an electric tool. If the wiring to the receptacle is incorrect, that
might be something to fix before using the outlet.
Ground Detector
The ground detector is an instrument which is used to detect conductor insulation
resistance to ground. An ohm meter, or a series of lights, can be used to detect the
insulation strength of an ungrounded distribution system. Most power distribution systems
in use today are of the grounded variety; however, some ungrounded systems still exist.
In the ground detector lamp method a set of three lamps connected through transformers to
the system is used. To check for grounds, the switch is closed and the brilliance of the lamps
is observed. If the lamps are equally bright, no ground exists and all the lamps receive the
same voltage. If anyone lamp is dark, and the other two lamps are brighter, the phase in
which the darkened lamp is in is grounded. In this case, the primary winding of the
transformer is shorted to ground and receives no voltage. This may seem like an antiquated
method but it works.

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Moving-Disk Frequency Meter
Moving-disk frequency meters are most commonly
out-of-circuit meters. They can be used to spot check
the frequency of power sources or equipment
signals. A moving-disk frequency meter having one
coil tends to turn the disk clockwise, and the other,
counterclockwise. Magnetizing coil A is connected in
series with a large value of resistance. Coil B is
connected in series with a large inductance and the
two circuits are supplied in parallel by the source.
For a given voltage, the current through coil A is practically constant. However, the current
through coil B varies with the frequency. At a higher frequency the inductive reactance is
greater and the current through coil B is less; the reverse is true at a lower frequency. The
disk turns in the direction determined by the stronger coil. A perfectly circular disk would
tend to turn continuously. This is not desirable, and so the disk is constructed so that it will
turn only a certain amount clockwise or counterclockwise about the center position, which
is commonly marked 60 hertz on commercial equipment. To prevent the disk from turning
more than the desired amount, the left half of the disk is mounted so that when motion
occurs, the same amount of disk area will always be between the poles of coil A. Therefore,
the force produced by coil A to rotate the disk is constant for a constant applied voltage.
The right half of the disk is offset, as shown in the figure. When the disk rotates clockwise,
an increasing area will come between the poles of coil B; when it rotates counterclockwise,
a decreasing area will come between the poles of coil B. The greater the area between the
poles, the greater will be the disk current and the force tending to turn the disk. If the
frequency applied to the frequency meter should decrease, the reactance offered by L
would decrease and the field produced by coil B would increase. The field produced by coil
A would remain the same. Thus, the force produced by coil B would tend to move the disk
and the pointer counterclockwise.
Selection of wire size
Several factors must be considered in selecting the size wire to be used for transmitting and
distributing electric power. There are military specifications that cover the installation of
wiring of ships and electrical/electronic equipment. These specifications describe the
technical requirements for material which is to be purchased from manufacturers by the
Department of Defense. One important reason for these specifications is to reduce the
danger of fires caused by the improper selection of wire sizes. Wires can carry only a limited
amount of current safely. If the current flowing through a wire exceeds the current-carrying
capacity of the wire, excess heat is generated. This heat may be great enough to burn off
the insulation around the wire and continue to do much greater damage by starting a fire.

39 | P a g e
Factors Affecting the Current Rating
The current rating of a cable or wire indicates the current capacity that the wire or cable can
safely carry continuously. If this limit, or current rating, is exceeded for a length of time, the
heat generated may bum the insulation. The current rating of a wire is used to determine
what size is needed for a given electrical load.
The following factors determine the current rating of a wire:
 The conductor size.
 The material of which the conductor is made.
 The location of the wire.
 The type of insulation used.
 Ambient temperature.
Materials
Marine cable insulation should be one of the following materials:
 Polyvinyl chloride (designated T). This is the most common type of insulation
currently used on modern vessels. It is a form of polymerized vinyl compound, resin,
or plastic. The maximum conductor temperature that the insulation can handle is
75C. The voltage range is a maximum of 600 volts. The maximum allowable ambient
temperature is 50C. It is of thermoplastic construction. This means it becomes soft
when heated and rigid when cooled and cured. Polyvinyl chloride-protected cable
provides a nonmetallic rigid sheathed cable. It is commonly called PVC.
Moisture-Resistant Jackets
An additional cable identification designation of I will be displayed on all cables with a
moisture-resistant jacket. The jacket will be composed of one of the following:
 Thermoplastic type T.
 Thermoplastic type T covered with a nylon coating, which changes the designator to
type N.
 Thermosetting chlorosulfonated polyethylene (type CP).
Separators and Fillers
Separators may be provided inside the insulation to allow free stripping of cable conductors.
Fillers eliminate air spaces in the cable. Marine cables will not permit the passage of water
along the inside of a cable, nor will they support conductor oxidation.
Additional insulating coding and specifications may be
found in the Recommended Practice for Electrical
Installations on Shipboard, the Institute of Electrical and
Electronics Engineers, Inc. (IEEE Standard 45).

40 | P a g e
Conductor Protection
Wires and cables are generally subject to abuse. The type and amount of abuse depends on
how and where they are installed and the manner in which they are used. Generally, except
for overhead transmission lines, wires or cables are protected by some form of covering.
The covering may be some type of insulator like rubber or plastic. Over this, an outer
covering of fibrous braid may be applied. If conditions require, a metallic outer covering may
be used. The type of outer covering used depends on how and where the wire or cable is to
be used.
Metallic armor provides a tough protective covering for wires or cables. The type, thickness,
and kind of metal used to make armor depend on three factors:
 The use of the conductors.
 The circumstances under which the conductors are to be
used.
 The amount of rough treatment that is expected.
Figure shows an armored cable. Basket-weave wire-braid armor
is used wherever a light and flexible protection is needed. In the past, this type of armor
covering has been used almost exclusively onboard ships. Wire braid is still used for special
purposes in the engineering spaces. The individual wires that are woven together to form
the braid are made out of aluminum or bronze. Besides mechanical protection, the wire
braid also provides a static shield. This is important in radio work aboard ship to prevent
interference from stray magnetic fields.
Wiring Techniques
Wire connections should be made inside the electrical component or inside watertight
feeder, branch, or connection boxes. These boxes are generally brass or bronze. Watertight
integrity is maintained by using stuffing tubes and gaskets. All the wire ends should be
provided with lugs for connecting to bus terminals or for bolting and insulating individual
wires together. During the course of normal electrical servicing, splicing wires is not
authorized.
Electrical cables must be continuous between the terminals except as outlined below:
 Component subassemblies may be spliced together. Splices may not be made to the
subassembly power supply cables or branch circuits.
 Cables may be spliced to extend a circuit when a vessel is receiving authorized
alterations.
 An extremely long cable may be spliced to allow its proper and efficient installation
as explained above.
 Splicing is authorized for repair of damaged cables if the remainder of the cable is in
good mechanical and electrical condition. The cable must be replaced in its entirety
at the most opportune time.

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When electrical casualty requires expedient repairs, it is absolutely necessary that the
repairs be made properly. A poor repair can prevent the operation of emergency equipment
or develop into a tire. Any electric circuit is only as good as its weakest link. The basic
requirement of any splice or connection is that it is both mechanically and electrically
sound.
The most common methods of making splices and connections in electrical cables are
explained below.
Splicing
Splices should be located in an
area that is easily accessible
and inspect able. The splice
should consist of the following
components:
 A conductor connector
(terminal lugs, splice
bolts, or splices)
 A replacement jacket for
the insulation.
 A shunt or suitable conductor to maintain the electrical continuity between two
severed pieces of the armor braid.
Warning
Continuity must be maintained between the armor covering and the vessel's hull at all times.

42 | P a g e
ASSIGNMENTS
1. What is electron?
2. Define P.D.
3. Write Symbol for voltage, current and resistance?
4. What is AC?
5. Write difference between AC and DC.
6. Write five types of conductors.
7. Define Watt?
8. What is Rectifier?
9. What is Zero Potential?
10. Draw the Symbol of capacitor, Diode and Inductor.
11. What is the meaning of LED?
12. Write the name of 3 types of Screw driver.
13. Write the purposes/uses of pliers.
14. Write different types of Circlip pliers.
15. What is working nature of an electric switch board?
16. Calculate the current for the given circuit. In 240 volt AC a water heater of 2000 watt
runs. What is rating of the circuit breaker?
17. Write the name of the instruments which are used for measuring power, voltage,
current, frequency and power factor?
18. Write the units of followings.
Power, Voltage, Current, Frequency, Resistance, Conductance.
19 How the tools are identified?
20. What is the process to find a cable to connect a load?

43 | P a g e
3.0 Electrical Circuits
OBJECTIVES: understand and to study the electrical circuit.
3.1 TYPES OF WIRES AND CONDUCTORS, LOAD CARRYING CAPACITY
A wire is a single, usually cylindrical, flexible
strand or rod of metal. Wires are used to bear
mechanical loads and to carry electricity and
telecommunications signals. Wire is commonly
formed by drawing the metal through a hole in a
die or draw plate. Standard sizes are determined
by various wire gauges. The term wire is also
used more loosely to refer to a bundle of such
strands, as in 'multistranded wire', which is more correctly termed a wire rope in mechanics,
or a cable in electricity. Although usually circular in cross-section, wire can be made in
square or flattened rectangular cross-section, either for decorative purposes, or for
technical purposes such as high-efficiency voice coils in loudspeakers. Edge-wound coil
springs, such as the "Slinky" toy, are made of special flattened wire.
Finishing, jacketing, and insulating
Electrical wires are usually covered with insulating materials, such as plastic, rubber-like
polymers, or varnish. Insulating and jacketing of wires and cables is nowadays done by
passing them through an extruder. Formerly, materials used for insulation included treated
cloth or paper and various oil-based products. Since the mid-1960s, plastic and polymers
exhibiting properties similar to rubber have predominated.
Two or more wires may be wrapped concentrically,
separated by insulation, to form coaxial cable. The wire or
cable may be further protected with substances like paraffin,
some kind of preservative compound, bitumen, lead,
aluminum sheathing, or steel taping. Stranding or covering
machines wind material onto wire which passes through
quickly. Some of the smallest machines for cotton covering
have a large drum, which grips the wire and moves it
through toothed gears; the wire passes through the centre
of disks mounted above a long bed, and the disks carry each
a number of bobbins varying from six to twelve or more in different machines. A supply of
covering material is wound on each bobbin, and the end is led on to the wire, which
occupies a central position relatively to the bobbins; the latter being revolved at a suitable
speed bodily with their disks, the cotton is consequently served on to the wire, winding in
spiral fashion so as to overlap. If a large number of strands are required the disks are

44 | P a g e
duplicated, so that as many as sixty spools may be carried, the second set of strands being
laid over the first.
Solid versus stranded
Stranded copper wire
Solid wire, also called solid-core or single-strand wire
consists of one piece of metal wire. Stranded wire is
composed of a bundle wires to make a larger conductor.
Stranded wire is more flexible than solid wire of the same
total cross-sectional area. Solid wire is cheaper to
manufacture than stranded wire and is used where there
is little need for flexibility in the wire. Solid wire also
provides mechanical ruggedness; and, because it has relatively less surface area which is
exposed to attack by corrosives, protection against the environment. Stranded wire is used
when higher resistance to metal fatigue is required. Such situations include connections
between circuit boards in multi-printed-circuit-board devices, where the rigidity of solid
wire would produce too much stress as a result of movement during assembly or servicing;
A.C. line cords for appliances; musical instrument cables; computer mouse cables; welding
electrode cables; control cables connecting moving machine parts; mining machine cables;
trailing machine cables; and numerous others. At high frequencies, current travels near the
surface of the wire because of the skin effect, resulting in increased power loss in the wire.
Stranded wire might seem to reduce this effect, since the total surface area of the strands is
greater than the surface area of the equivalent solid wire, but ordinary stranded wire does
not reduce the skin effect because all the strands are short-circuited together and behave as
a single conductor. A stranded wire will have higher resistance than a solid wire of the same
diameter because the cross-section of the stranded wire is not all copper; there are
unavoidable gaps between the strands (this is the circle packing problem for circles within a
circle). A stranded wire with the same cross-section of conductor as a solid wire is said to
have the same equivalent gauge and is always a larger diameter.
Galvanized: You can find this (along with copper wire) in most hardware stores. It is a dull
silver color and is also good practice wire. This wire is harder than the silver wire you may be
used to, so get a small gauge if you plan to get some.
Sterling Silver: This is one of my favorite types of wire because sterling wire works the best
for many of my finished jewelry pieces. Sterling indicates that the wire is 92.5% pure silver.
The rest is made up of alloys (such as copper or zinc) to provide strength. Sterling will
tarnish, called oxidation, so it's best to keep in zip lock bags or sealed containers of some
kind when not using it for jewelry or wearing the jewelry itself. When it does tarnish (and it
eventually will), you can polish by using a polishing kit, using a magnetic polisher or tumbler,
or you can clean it with an ionic cleaner.

45 | P a g e
Fine Silver: Made of 99.9% pure silver, many wire workers enjoy working with fine silver.
Fine silver is softer than sterling. Since it has fewer alloys, it also does not tarnish as quickly
as sterling silver does.
Gold-filled: First of all, never call gold-filled wire, "gold wire." It is used many times by
jewelry makers, while gold-filed metal has many layers of gold, it is not pure gold. On the
upside, gold-filled is of much better quality than plated gold (only one layer) so gold-filled
lasts for a very long time if cared for properly. It is a wonderful alternative to gold, which is
pretty darn expensive!
Gold: If you are daring enough and feel comfortable enough, go for the gold! Many jewelry
vendors offer real gold wire in various karats (10-24 for example) and even different colors.
Coated Colors: Often coated wire is coated with an enamel to create the color of the wire.
This wire has become very popular and is even available in many large craft stores. It is a lot
of fun to work with. However, due to the coating, it can be marked by metal tools, so keep
this in mind when using it.
1. Triplex Wire
Triplex is an aerial cable that the utility company uses to feed the power
pole. This wire ties to the wires sticking out of the weather head.
2. Main Feeder Wires
These wires are usually type THHN wire and are rated for 125% of the load
required. These are usually black insulated wires coming out of the service
weather head.
3. Panel Feed Wires
These wires are also type THHN, like the main feeders. A typical 100-amp
service would have a #2 THHN set of wires. They would then be rated at
125 amps. This would protect the wires if the amperage was a full 100
amps.
4. Non-Metallic Sheathed Wire (NM)
This wire, commonly called Romex, is a plastic coated
wire that has either two or three conductors and a
bare ground wire. This is the typical wiring used in
most homes. The rating for this wire is either 15
amps, 20 amps, or 30 amps, depending on the installation.

46 | P a g e
5. Single Strand Wire
When your home is piped, you’ll have to have another type of wire. Single strand wire is
insulated and many of these can be pulled into the same pipe. Normally, you’ll be using
THHN wire for this installation.
Types of Conductors in Transmission Lines
A conductor is a material that facilitates the flow of
electricity (or electric current) through a transmission
line. Different types of conductors are used in
transmission lines. They vary in number and size,
depending on the type of circuit and the transmission
voltage. Steel, aluminum and copper are the most
common conducting materials used in transmission lines.
Copper:
Copper is abundantly available in nature, is an excellent conductor of electricity and can be
readily spliced. Copper conductors exist in one of three forms: soft drawn (or annealed),
medium drawn and hard drawn. Soft-drawn copper conductors are commonly used in short
transmission line spans and to ground electrical systems. They are flexible and resistant to
breaking even under high stress. Medium-drawn copper conductors are used for medium-
range distribution lines, while hard-drawn copper conductors are used in longer spans
(greater than 200 feet) and are the strongest of the three. Their strength, however, makes
them inflexible and often difficult to work with.
Steel
According to "The Electronics Handbook," steel conductors are one tenth as effective as
copper conductors and rust easily--due to which steel conductors are hardly used alone.
Steel conductors are commonly galvanized (or coated with a layer of zinc to counteract their
rusting tendency). According to "Guide to Electrical Power Distribution Systems," steel-
based transmission conductors are three to five times stronger than copper conductors, and
can be used for longer spans with fewer supports.
Aluminum
According to "Electrical Craft Principles," Volume 1, aluminum can rapidly oxidize, has higher
thermal expansion, lower strength, and less than half the conductivity of copper. It is,
however, lighter and half as resistant as copper. There are two types of aluminum
commonly used as transmission line conductors: heat-treatable alloy and pure metal grade.
Aluminum conductors are commonly used for higher-voltage overhead transmission lines,
power cables, busbars, motors, heating elements, heat sinks and foil windings.

47 | P a g e
Steel-Reinforced Aluminum
Steel-reinforced-aluminum conductors are commonly used in medium-, high- and extra-
high-voltage (EHV) transmission lines. They are also called ACSR or aluminum-conductor
steel-reinforced conductors. ACSR transmission lines are high-strength, high-capacity and
exhibit excellent conductivity. They are lightweight and used in overhead transmission lines,
river crossings and longer spans. ACSR transmission lines have a central steel strand,
surrounded by outer aluminum strands. The steel conductor supports the weight of the
transmission line while the aluminum is used for its conductive properties. ACSR
transmission cables are available in specific sizes and varying amounts of central steel
strands as well as outer aluminum conductors.
3.2 WIRING DIAGRAMS.
A wiring diagram is a simplified conventional pictorial representation of an electrical circuit.
It shows the components of the circuit as simplified shapes, and the power and signal
connections between the devices. A wiring diagram usually gives more information about
the relative position and arrangement of devices and terminals on the devices, to help in
building the device.
This is unlike a
schematic diagram
where the
arrangement of the
components
interconnections on
the diagram does not
correspond to their
physical locations in
the finished device. A
pictorial diagram
would show more
detail of the physical appearance, whereas a wiring diagram uses a more symbolic notation
to emphasize interconnections over physical appearance.
A wiring diagram for parts of an electric guitar, showing semi-pictorial representation of
devices arranged in roughly the same locations they would have in the guitar. A wiring
diagram is used to troubleshoot problems and to make sure that all the connections have
been made and that everything is present. An automotive wiring diagram, showing useful
information such as crimp connection locations and wire colors. These details may not be so
easily found on a more schematic drawing.

48 | P a g e
House/ Residential Wiring Diagram of a Typical Circuit
Lighting Circuit Diagrams
These diagrams show various methods of one, two and multiple way switching.
L and N indicate the supply. Switches are shown as dotted rectangles. Earth wires are not
shown.
One way switching two way switching, 2 wires
This arrangement would typically be used in
conduit, and uses two wires between each
switch.
It can also be used in domestic properties by
using twin earth cable between the switches,

49 | P a g e
and 1core+earth from the switches to the ceiling rose.
Unfortunately, this is usually uncounted in stairwells, with the line from the downstairs
lighting circuit and the neutral connected to the upstairs lighting circuit. Such an
arrangement is not permitted, as isolating only one of the circuits leaves live wiring
depending on the position of the light switches.
Two way switching, 3 wires
More common in domestic properties. Twin earth from the ceiling rose to the first switch,
and three wires between the switches, usually 3 core and earth cable.
This is also known as the 'conversion' method, since it is the easiest way to add a second
light switch to an existing circuit.
Three way switching, 3 wires Three way switching, 2 wires
Three wires between the two end switches,
probably using 3 core and earth cable. Usually the third wire passes the middle intermediate
switch but is joined in a separate terminal block.
Two wires between each switch. Most likely to be found with wires in conduit. The middle
switch is an intermediate type.

50 | P a g e
Industrial Wiring
When wearegoing for industrial wiring it’s
different ,weare using two types of circuits
control & power circuit.
In control circuit we control all the switching
device & and the coil parts,but in case of power
circuit we control motor with three phase supply.
3-Phase motor control circuit

51 | P a g e
Over Head Line
An overhead line, or overhead wire, is used to transmit electrical energy to trams,
trolleybuses or trains at a distance from the energy supply point. It is known variously as
 Overhead contact system (OCS)
 Overhead line equipment (OLE or OHLE)
 Overhead equipment (OHE)

52 | P a g e
 Overhead wiring (OHW) or overhead lines (OHL)
 Catenary
In this article the generic term overhead line is used. This is
also the term used by the International Union of Railways.
Overhead line is designed on the principle of one or more
overhead wires or rails (particularly in tunnels) situated
over rail tracks, raised to a high electrical potential by
connection to feeder stations at regular intervals. The
feeder stations are usually fed from a high-voltage electrical
grid.
Overview
Electric trains that collect their current from an overhead
line system use a device such as a pantograph, bow
collector, or trolley pole. The device presses against the
underside of the lowest wire of an overhead line system,
the contact wire. The current collectors are electrically
conductive and allow current to flow through to the train or
tram and back to the feeder station through the steel
wheels on one or both running rails. Non-electric trains (such as diesels) may pass along
these tracks without affecting the overhead line, although there may be difficulties with
overhead clearance. Alternative electrical power transmission schemes for trains include
third rail, ground-level power supply, batteries, and electromagnetic induction.
This article does not cover regenerative braking, where the traction motors act as
generators to retard movement and return power to the overhead.
Typical constructions of overhead lines
Along streets, alleys, through woods, and in backyards, many of the distribution lines that
feed customers are overhead structures.
Because overhead lines are exposed to trees and animals, to wind and lightning, and to cars
and kites, they are a critical component in the reliability of distribution circuits. Overhead
constructions come in a variety of configurations.
Normally one primary circuit is used per pole, but utilities sometimes run more than one
circuit per structure. For a three-phase circuit, the most common structure is a horizontal
layout with an 8- or 10-ft wood crossarm on a pole. Armless constructions are also widely
found where fiberglass insulator standoffs or post insulators are used in a tighter
configuration.
Utilities normally use 30- to 45-ft poles, set 6 to 8 ft deep. Vertical construction is also
occasionally used. Span lengths vary from 100 to 150 ft in suburban areas to as much as 300
or 400 ft in rural areas.

53 | P a g e
Distribution circuits normally have an under built neutral — the neutral acts as a safety
ground for equipment and provides a return path for unbalanced loads and for line-to-
ground faults. The neutral is 3 to 5 ft below the phase conductors.
Utilities in very high lightning areas may run the neutral wire above the phase conductors to
act as a shield wire.

54 | P a g e
Example cross arm construction
Some utilities also run the neutral on the crossarm. Secondary
circuits are often run under the primary. The primary and the
secondary may share the neutral, or they may each have their
own neutral. Many electric utilities share their space with
other utilities; telephone or cable television cables may run
under the electric secondary.
Wood is the main pole material, although steel, concrete, and
fiberglass are also used. Treated wood lasts a long time, is
easy to climb and attach equipment to, and also augments the
insulation between the energized conductors and ground.
Conductors are primarily aluminum. Insulators are pin type, post type, or suspension, either
porcelain or polymer.
The National Electrical Safety Code (IEEE C2-2000) governs many of the safety issues that
play important roles in overhead design issues. Poles must have space for crews to climb
them and work safely in the air. All equipment must have sufficient strength to stand up to
“normal” operations. Conductors must carry their weight, the weight of any accumulated
ice, plus withstand the wind pressure exerted on the wire.

55 | P a g e
3.3 CONDUCTORS AND INSULATORS
Conducting Material
It is the part of the
accessory through which
the current passes. It is
usually made of copper or
brass. Its current rating
depends on the maximum
current that can flow
through it without pro-
ducing any harm. For
example, if a switch is
designed for 15 A, it means
that we can easily pass 15 A through its conducting material, but on passing higher current
then specified, say 15 A, it will be overheated and may burn due to sparking, etc. Thus, the
use of a particular accessory is limited only for the current rating specified.
A neutrally charged conductor and its response to charged objects being brought near it. In
a conductor (usually metal) many of the electrons are free to to move around within the
conductor. Conductors are often referred to as
having a "sea of electrons" since the movement
of the electrons looks like a flowing sea.
As the positively charged rod is brought near
the conductor, the electrons are attracted
toward the charged rod. This causes a force of attraction to be created between the rod and
the conductor.
As the negatively charged rod is brought near the conductor, the electrons are repelled
away from the charged rod. This causes a force of attraction to be created between the rod
and the conductor. As a result, we can say that
a charged object will always be attracted by a
conductor.
Notice that only the electrons are free to move,
the protons are fixed in place because they
make up the mass of the conductor. It is also
important to notice that when no charged
object is near the conductor, the electrons
evenly distribute themselves within the
conductor.

56 | P a g e
Insulating Material
It is the substance which binds the current to flow in a definite direction, or in other words,
the substance which does not allow the leakage current to flow through. Their rating is
considered according to the maximum safe working voltage at which no leakage of current
can take place through the insulation. If the rating of the switch is 250 V, it means the
insulation can withstand 250 V and there will be no leakage current, but at a higher value of
voltage, the current could leak through the insulation. The insulating material that is used
for electrical accessories is either Bakelite or porcelain.
The animation at the left is showing a neutrally charged insulator and its response to a
charged object being brought near it. In an insulator (such as plastic, rubber, glass, etc) the
electrons are not free to move around the entire object. They are generally restricted to
moving only around the atom they are attached to. They can move from one side of the
atom to the other but are unable to leave the atom. As a result, we say that charges stay
where you put them on an insulator.
Notice in the animation that the electrons are evenly distributed but are still attached to
only one of the positive charges. As the negatively charged rod is brought near the insulator,
notice that the electrons move to the other side of the positive charges but are unable to
move completely to the far side of the object. Even though the charges only move to the
other side of the atom you should notice that the upper side of the insulator becomes more
positive and therefore feels a force of attraction to the the charged object. There would also
be an attraction if the object was positively charged. as a result we say that a neutral
insulator will always be attracted to a charged object.
Insulator
A substance which (at a particular voltage) does not allow the flaw of electrons (current)
through them is called an insulator. For example, some of the good insulators are mica,
porcelain, glass, rubber, Bakelite, etc.
In insulators the electrons are closely and strongly bound to the nucleus. There are very few
free electrons in them and the interchange between atoms is little. Therefore, insulators do
not conduct any electric current or conduct very little if a very high potential difference is
applied across them.
Qualities of Insulating Materials
The following are the main qualities of good insulating materials which should be consider-
ed while selecting a particular one for use:
 It should be flexible.
 It should have good mechanical strength.
 It should be non absorptive of moisture.

57 | P a g e
 It should be easily molded to any shape.
 It should be noninflammable.
 It should not be affected by acids or alkalies.
It should have high specific resistance to reduce the possibilities of leakage current. It should
be capable of working at high temperature because insulators lose their insulating proper-
ties as the temperature increases.
It should have high dielectric strength, i.e. the value of the voltage at which the breakdown
takes place in a plate of insulator 1 mm thick should be high. Dielectric strength of an insu-
lator is measured in kilovolts per millimeter thickness.
The majority of insulating materials available for use in the construction of electrical machi-
nes and apparatus have only a few of the above mentioned properties. It is, therefore, the
work of the designer to select a particular insulation for the purpose for which it is required.
Application of conductor and insulator
In the application of electrical wiring: the conductor (e.g. copper) carries the electricity
where it is needed the insulator (e.g. PVC) around the conductor keeps the electricity from
going where it...
3.4 CONCEPTS OF AC, DC, SINGLE PHASE AND 3 PHASE SUPPLY
Alternating Current (AC)
Alternating Current (AC) flows one way, then the
other way, continually reversing direction.
An AC voltage is continually changing between
positive (+) and negative (-).
The rate of changing direction is called the frequency of the AC and it is measured in hertz
(Hz) which is the number of forwards-backwards cycles per second.
Mains electricity in the India has a frequency of
50Hz.
See below for more details of signal properties.
An AC supply is suitable for powering some
devices such as lamps and heaters but almost all
electronic circuits require a steady DC supply (see below).

58 | P a g e
Direct Current (DC)
Steady DC
from a battery or regulated power supply, this is
ideal for electronic circuits.
Smooth DC
from a smoothed power supply, this is suitable for
some electronics component.
Direct Current (DC) always flows in the same
direction, but it may increase and decrease.
A DC voltage is always positive (or always
negative), but it may increase and decrease.
Electronic circuits normally require a steady DC supply which is constant at one value or a
smooth DC supply which has a small variation called ripple.
Cells, batteries and regulated power supplies provide steady DC which is ideal for electronic
circuits.
Power supplies contain a transformer which converts the mains AC supply to a safe low
voltage AC. Then the AC is converted to DC by a bridge rectifier but the output is varying DC
which is unsuitable for electronic circuits.
Varying DC
Properties of electrical signals from a power supply without smoothing, this is not suitable
for electronics.
An electrical signal is a voltage or current which conveys information, usually it means a
voltage. The term can be used for any voltage or current in a circuit.
The voltage-time graph on the right shows various properties of an electrical signal. In
addition to the properties labeled on the graph, there is frequency which is the number of
cycles per second.
The diagram shows a sine wave but these properties apply to any signal with a constant
shape.

59 | P a g e
Amplitude
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
Peak-peak voltage is twice the peak voltage (amplitude). When reading an oscilloscope trace
it is usual to measure peak-peak voltage.
Time period
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
microseconds (µs) are often used. 1ms = 0.001s and 1µs = 0.000001s.
Frequency
Frequency is the number of cycles per second. It is measured in hertz (Hz), but frequencies
tend to be high so kilohertz (kHz) and megahertz (MHz) are often used. 1kHz = 1000Hz and
1MHz = 1000000Hz.
frequency =
1
and time period =
1
time period frequency
Mains electricity in the India has a frequency of 50Hz,
so it has a time period of 1
/50 = 0.02s = 20ms.
Root Mean Square (RMS) Values
The value of an AC voltage is continually changing from zero
up to the positive peak, through zero to the negative peak
and back to zero again. Clearly for most of the time it is less
than the peak voltage, so this is not a good measure of its
real effect.
Instead we use the root mean square voltage (VRMS) which is 0.7 of the peak voltage (Vpeak):
VRMS = 0.7 × Vpeak and Vpeak = 1.4 × VRMS
These equations also apply to current.
They are only true for sine waves (the most common type of AC) because the 0.7 and 1.4
are different values for other shapes.
The RMS value is the effective value of a varying voltage or current. It is the equivalent
steady DC (constant) value which gives the same effect.
What do AC meters show, is it the RMS or peak voltage?

Industrial Electrician Handbook: Safety, Electrical Basics & More

Industrial Electrician Handbook: Safety, Electrical Basics & More

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