AMT AV801 M-3 Electrical Fundamentals Biruke.pptx

Welcome to
AMT/AV801: M-3 Electrical Fundamentals

Self Introduction
Your Name
Your expertise and Experience
Your current job title
A little something about you that would
interest your colleagues 
Your Expectations about this course

Administrative Aspects
Cell Phones
Breaks and Lunch
Exams
Participation
References
Activities & Events
Punctuality

Objectives
At the end of the topic you will be able to:
 Identify basic electrical principles and terminologies
applicable to aircraft electrical systems.
 Identify Electrical components such as resistors,
inductors, transformers that are used in aircraft
electrical circuits & systems.
 Identify different types of electrical machines that are
used in aircraft electrical systems.

Static Electricity
& Conduction
Generation of
Electricity
Electrical
Terminology
Electron Theory
DC Sources of
Electricity
Module Structure -1
Lesson 1 Lesson 2 Lesson 3
Lesson 4 Lesson 5

Resistance/Resist
ors
Magnetism and
Electromagnetism
Capacitance/Capa
citors
DC Circuits
Inductance/
Inductors
Module Structure -2
Lesson 6 Lesson 7 Lesson 8
Lesson 9 Lesson 10

AC Theory Transformers
AC Generators
Lesson 12 Lesson 13
Lesson 14
DC Motor/
Generator Theory
Lesson 11
Module Structure -3

Lesson 1Content
• Atomic Structure and Distribution of Charges with in
• Atom
• Molecules
• Ions
• Compounds
• Molecular Structure of
• Conductors,
• Semiconductors
• Insulators

Definition
What is an electricity?
• Electricity is a study of generation, distribution and
utilization of electrical energy.
• It is produced from the flow of electrons through a
conductor.
• Electricity is one of the energy sources which we
use for our daily consumption.

Application of Electricity in Aircraft
• Aircraft system uses electricity for different functions.
• Aircraft electrical systems
• generate, regulate and distribute electrical power
throughout the aircraft.
• New-generation aircrafts rely heavily on electrical
power
• because of the wide use of electronic flight instrument.

Application of Electricity in Aircraft -2
• Typical application of electricity in aircraft
includes:
• Cabin lighting,
• Operation of entertainment systems,
• Ignition of engines,
• Operation of communication & navigation
system etc.
PPT 1.9 ET-AV01:Electrical Fundamentals Rev No.0

1.1. Atomic Structure and Distribution of Charges
Atom
• The term "atom" comes from the Greek word for
indivisible
• Atomic theory of matter states that all matter is
composed of small fast moving particles called
Atom.

Atom
• Atoms are the basic building
blocks of matter.
• They are composed of three
subatomic particles:
protons(+), neutrons, and
electrons(-).

Atom
• Protons and neutrons are found in the nucleus of the
atom, while electrons orbit the nucleus.
• The number of protons in an atom determines its
atomic number, which is unique for each element.
• The number of protons in an atom's nucleus is called
its atomic number.
• Atoms are electrically neutral, with electrons equal to
protons.

Molecules
• It consists of one or more atoms, of the same
types joined together

Ion
• An atom or group of atoms that carries a
positive(+) or negative(-) electric charge as a
result of having lost or gained one or more
electrons

Ion
• Neutral atom contains an equal number of protons
and electrons is called ions.
• An atom gains electron is negative ion.
• An atom loses electron is positive ion

Molecular
• It consists of one or more atoms, of the same or
different types joined together

Difference between
a molecule and a
compound

1.2. Molecular Structure
Definition
• Valence band: The highest band filled with
electrons in a solid, tightly bound to atoms and
cannot move freely.
• Conduction band: empty or partially filled with
electrons in a solid, allowing free movement
without atom binding.

• Electrical conductivity is determined by the
number of electrons in a material's conduction
band
• high conductivity indicating good electricity,
• low conductivity indicating poor conductivity.
• Energy gap measures energy difference between
valence and conduction bands, affecting electron
movement.

1.2.1 Conductors:
• Materials that allow the flow of electric current
easily.
• They have a large number of free electrons that
can move freely throughout the material.
• Examples: metals, such as copper, silver, and
gold.

1.2.2 Insulators:
• Materials that do not allow the flow of electric
current easily.
• They have a very small number of free electrons
that cannot move freely throughout the material.
• Examples: plastics, rubber, and glass.

1.2.3 Semiconductors:
• Materials that have an electrical conductivity that
falls between that of a conductor and an insulator.
• Material has fewer free electrons than conductors,
allowing them to move freely.
• Examples: silicon, germanium, and gallium
arsenide.

Summary
• Atom: The basic unit of matter. It is made up of three subatomic
particles: protons, neutrons, and electrons.
• Conductor: A material that allows the flow of electric current
easily.
• Insulator: A material that does not allow the flow of electric
current easily.
• Semiconductor: A material that has an electrical conductivity
that falls between that of a conductor and an insulator.
• Energy gap: The difference in energy between the valence band
and the conduction band in a semiconductor.

Learning Check
 What are the three main subatomic particles that make up an atom?
 What is the difference between protons, neutrons, and electrons?
 Where are protons, neutrons, and electrons located in an atom?
 What is an ion?
 What is a compound?
 What are conductors?
 What are insulators?
 What are semiconductors?
 What is the energy gap of a semiconductor?
 What are some examples of semiconductors?

Static Electricity & Conduction

Lesson 2 Content
• 2.1. Static Electricity
• 2.2. Distribution of Electrostatic Charges
• 2.3. Electrostatic Laws of Attraction & Repulsion
• 2.4. Units of Charge & Coulomb's Law
• 2.5. Conduction of Electricity In Solids, Liquids,
Gases & Vacuum
• 2.6. Static Electricity & Aircraft

2.1. Static Electricity
• As the name implies, it is the study of stationary
electric charges.
• It is the result of an imbalance between negative
and positive charges that build up on the surface
of an insulator until they find a way to be
discharged
• Static electricity is usually caused by the rubbing
together of non-conductiv materials, such as a
balloon and your hair.

2.1. Static Electricity
Lightening
• Static Charge Build-up in the Clouds
• The precursor of any lightning strike is
the polarization of positive and negative charges
within a storm cloud.
• The tops of the storm clouds are known to acquire an
excess of positive charge and the bottoms of the
storm clouds acquire an excess of negative charge.

2.2. Distribution of Electrostatic Charges
• Electrostatic charges can be distributed evenly on an
object, or they can be concentrated in certain areas.
• The way that electrostatic charges are distributed on
an object depends on the material that the object is
made of.
• For example, metals tend to distribute electrostatic
charges evenly, while insulators tend to concentrate
electrostatic charges in certain areas.

2.3. Electrostatic Laws of Attraction & Repulsion
• The electrostatic laws of attraction and repulsion
state that:
• Like charges(+&+)(-&-) repel each other.
• Unlike charges (+&-) attract each other.
• Attraction/repulsion force is proportional to
product of charges and inversely proportional to
distance.

2.4. Units of Charge & Coulomb's Law
• The unit of charge in the International System of Units
(SI) is the coulomb (C).
 One coulomb = 6.29 x 1018 electrons
• Coulomb's law states that the force of attraction or
repulsion between two charges is:
• Proportional to the product of the charges.
• Inversely proportional to the square of the distance between
the charges.
• Measured in newtons (N).

2.5. Conduction of Electricity In
• Solids, liquids, gases, and vacuum can all conduct
electricity.
• The way that electricity is conducted in these different
states of matter depends on the properties of the
material.
• For example, metals are good conductors of electricity
in all states of matter.
• Insulators are poor conductors of electricity in all
states of matter.

2.6. Static Electricity & Aircraft
• Static electricity can be a problem for aircraft
because it can build up on the surface of the
aircraft and cause a spark.
• This spark can ignite flammable materials on
board the aircraft, such as fuel or oxygen.
• To prevent static electricity build-up on aircraft,
they are often sprayed with a conducting liquid,
such as water or alcohol.

How Static Electricity Builds Up on Aircraft?
• As an aircraft moves through the air, it rubs against
the air molecules, which can cause the aircraft to build
up a static charge.
• The amount of static charge that builds up depends
on the humidity of the air, the speed of the aircraft,
and the materials that the aircraft is made of.
• Dry air is more conductive than humid air, so static
electricity is more likely to build up in dry air.

How Static Electricity Builds Up on Aircraft?
• Faster-moving aircraft build up more static charge
than slower-moving aircraft.
• Aircraft that are made of non-conducting
materials, such as plastic, are more likely to build
up static charge than aircraft that are made of
conducting materials, such as metal.

How Static Electricity Can Cause Problems
• If the static charge on an aircraft builds up to a high
enough level, it can discharge, creating a spark.
• This spark can ignite flammable materials on board
the aircraft, such as fuel or oxygen.
• A spark from static electricity could also damage
electrical equipment on board the aircraft.
• This could cause the aircraft to lose control or even
crash.

How to Prevent Static Electricity Build-up on
• Aircraft use conducting materials like aluminium to
dissipate static charges.
• Ground aircraft before refuelling or taking off to
equalize electrical potential and prevent sparks.
• Anti-static sprays prevent static charge build-up
on aircraft surfaces.

Lesson 3
Electrical Terminology

Objectives
 Define voltage and potential difference.
 Explain the difference between voltage and
electromotive force (emf).
 Describe the relationship between voltage and
current.
 Define conventional flow and electron flow.
 Define conductance and conductivity.
 Identify the units of measurement for voltage, current,
resistance, conductance, and conductivity.

Introduction
• Understanding basic electrical terminology is
crucial for comprehending electricity's functioning.
• Key electrical terms discussed: potential
difference, force, voltage, charge, current.

3.1 VOLTAGE
• The electrical equivalent of mechanical potential,
influences potential energy in an electrical supply.
• The voltage of a circuit is the sum of the EMFs of
the batteries in the circuit and the voltage drops
across the resistors in the circuit.

3.1.1 Potential Difference
• Potential difference is the difference in electrical
potential energy between two points.
• It is measured in volts (V).
• The greater the potential difference between two
points, the greater the force that will cause
electrons to flow between them.

3.1.2 Electromotive Force (EMF)
• Electromotive force (EMF) is the force that causes
electrons to flow in a circuit.
• It is measured in volts (V).
• Without EMF there will be no current.

3.2 Current
• Current is the flow of charge through a conductor.
• It is measured in amperes (A).
• The current in a circuit is equal to the voltage
divided by the resistance.

3.2.1 Charge
• Charge is the property of matter that causes it to
experience a force when it is placed in an electric
field.
• Charge is measured in coulombs (C).
• There are two types of charge: positive charge
and negative charge.
• Like charges repel each other, and unlike charges
attract each other.

3.2.2 Conventional Current Flow
• Conventional current flow is the flow of positive
charge through a conductor.
• It is the opposite of the actual flow of electrons.

3.2.3 Electron Flow
• Conventional current flow is the flow of positive
charge through a conductor.
• It is the opposite of the actual flow of electrons.

3.3 Resistance
• Resistance is the opposition to the flow of current
in a conductor.
• It is measured in ohms (Ω).
• The greater the resistance of a conductor, the less
current will flow through it.

3.3.1 Conductance
• Conductance is the ability of a conductor to allow
current to flow through it.
• It is measured in siemens (S).
• The greater the conductance of a conductor, the
more current will flow through it.

Learning Check
 What is voltage?
 What is potential difference?
 What is electromotive force (emf)?
 What is the relationship between voltage and current?
 What are the units of resistance?
 What is conductance?

Lesson 4
Generation of Electricity

Objectives
 To introduce the concept of electricity and how it is
generated.
 To discuss the four main methods of electricity
generation: light and heat, friction and pressure,
magnetism and motion, and chemical action.
 To explain how a generator works and the
advantages and disadvantages of each method of
electricity generation.

Introduction
• Electricity is a form of energy that can be used to
power many different devices.
• It is generated by converting other forms of
energy, such as heat, light, motion, and chemical
energy.
• The most common way to generate electricity is
by using a generator.

4.1. Production of Electricity by
• Electrical energy is stored in atoms of materials,
but cannot be used for practical purposes.
• External energy, including friction, pressure,
magnetism, heat, light, and chemical action,
separates electrons from nuclei.

4.1. Production of Electricity by
• Light and heat: Electricity can be generated by using light
or heat to create a current in a conductor.
• Friction and pressure: Electricity can be generated by
rubbing two objects together, or by applying pressure to a
conductor.
• Magnetism and motion: Electricity can be generated by
moving a magnet inside a coil of wire, or by moving a
conductor through a magnetic field.
• Chemical action: Electricity can be generated by the
chemical reaction of two substances.

4.1.1. Light
• A photovoltaic cell generates an emf when light
falls onto it. Example: selenium photovoltaic cell

4.1.2. Heat
• When a material is heated, its electrons gain
energy and move more freely. This creates an
electric current.

4.1.3. Friction
• Static electricity occurs when electrons are
separated and build-up in two bodies due to
friction. Early examples include rubbing glass rods
with silk stockings, and ebonite rods with cats fur.

4.1.4. Pressure
• The piezoelectric emf is
an emf produced by
crystals and
semiconductors under
mechanical pressure
changes, reversing
polarity.

4.1.5. Magnetism & Motion
• Magnetism is not the direct source
of external energy; generators use
its properties to produce external
energy, breaking electrons away
from nuclei and allowing electric
current flow.

4.1.6. Chemical Action
• It is the particular kind of
chemical action that takes
place in ‘electric cells’ and
‘batteries’ which is put to
practical use in the production
of electricity.

Summary
• There are many different ways to generate
electricity.
• The most common method is to use a generator,
which converts mechanical energy into electrical
energy.
• Other methods of electricity generation include
using light, heat, friction, magnetism, and
chemical action.

Learning Check
1. What are the four main methods of electricity generation?
2. What is a generator?
3. How does a generator work?
4. What are some of the advantages and disadvantages of each method of
electricity generation?
5. What is a thermocouple and how does it work?

Lesson 5
DC Sources of Electricity

Introduction
• Construction and basic chemical action of primary
cells and secondary cells
• Cells connected in series and parallel
• Internal resistance and its effect on a battery
• Construction, materials, and operation of
thermocouples
• Operation of photocells

Objectives
 Define a DC source of electricity.
 Explain the difference between primary and
secondary cells.
 Describe how cells are connected in series and
parallel.
 Explain the concept of internal resistance.
 Describe the construction and operation of
thermocouples.
 Explain the operation of photocells.

Outline
• 5.1. Construction & Basic Chemical Action of:
• 5.1.1. Primary Cells
• 5.1.2. Secondary Cells
• a. Lead Acid Cells
• b. Nickel Cadmium Cells
• c. Other Alkaline Cells
• 5.2. Cells Connected In Series & Parallel
• 5.3. Internal Resistance & Its Effect on a Battery
• 5.4. Construction, Materials & Operation of Thermocouples
• 5.5. Operation of Photo-Cells

5. DC Sources of Electricity
• A DC source of electricity is a device that
produces a constant direct current.
• Direct current is a flow of electric charge in one
direction only.

5. DC Sources of Electricity
• Large amounts of useable power can only be
produced chemically or by generation On an
aircraft:
• The battery may be used for
• engine starting
• source of emergency power when the generator fails

5.1.1. Primary Cells
• A primary battery or primary cell is a battery is
designed to be used once and discarded.
• In general, the electrochemical reaction occurring
in the cell is not reversible, rendering the cell un-
rechargeable.
• The formats include AAA, AA, C, D, and Snap-On
9-volt batteries.

5.1.2. Secondary Cells
• Secondary cells are cells that can be recharged.
They are typically used in devices that require a
lot of power, such as laptops Aircraft, and cell
phones.
• The process of reversing the chemical action is
referred to as charging and entails passing a
current through the cell.

Primary and Secondary
• Cells may be connected in series, parallel or any
combination of the two in order to form a battery
• When cells are connected to form a battery they
should be of similar construction, have the same
terminal voltage, internal resistance and capacity.

When connected in series:
1. The battery voltage is the total of the
individual cell voltages.
2. The battery resistance is equal to the total of the
individual cell resistance’s.
3. The battery capacity is the same as the
capacity of a single cell.

Primary and
shows the Series interconnection
of battery cells.

When connected in parallel:
1. The battery voltage is the same as the
voltage of a single cell.
2. The battery resistance is equal to the parallel
total of the cell resistance’s.
3. The battery capacity is equal to the total of
the individual cell capacities.

shows parallel connection of
battery cells.

Chemical Action of Dry
• In cells, an electrolyte separates two charge-collecting
materials called electrodes
• The electrolyte pushes electrons onto one of the
plates and takes them off the other.
• Electrolytes are chemical solutions to allow the
generation and free movement of both types of ions
• Electrolytes are acid or alkaline pastes or liquids

Chemical Action of Dry
• in carrying electrons between plates is a
chemical reaction of electrolyte and the two
plates.
• This action changes chemical energy into
electrical charges.

5.1.2. a. Lead Acid Cells
• Lead acid cells have a nominal voltage of 2 Volts,
therefore a typical 24V aircraft battery would
consist of 12 cells connected in series. The active
material in the positive plates is Lead Peroxide
(Pb02) the negative plates, Spongy Lead (Pb).
The electrolyte is dilute sulphuric acid (2H2SO4).
• Currently it is used on light A/C

5.1.2. b. Nickel Cadmium Cells
• Due to its properties and
advantages, it is taking over
lead acid-based batteries
and gaining popularity in
recent times.
• Each cell has a lower
voltage, therefore more cell
are required to produce a
battery.

5.1.2. b. Nickel Cadmium Cells
• The plates of a nickel cadmium battery are made
a nickel plated steel screen with nickel carbonyl
powder
• The positive plate of nickel cadmium battery is
Nickel hydroxides
• The negative plate of nickel cadmium battery is
cadmium.

5.3. Internal Resistance & Its Effect on a Battery
• is the resistance of the materials inside a cell. It
limits the amount of current that can flow through
the cell.
• There are two basic components that impact the
internal resistance of a battery:
• electronic resistance
• ionic resistance.

5.4. Thermocouples
• Thermocouples are devices that convert heat into
electricity.
• They are made of two different metals that are joined
together.
• When the two metals are heated, a voltage is
generated.
• The amount of voltage generated depends on the
difference in temperature between the two metals.

Operation of Photo-Cells
• Photocells are devices that convert light into
electricity.
• They are made of a semiconductor material that
absorbs light.
• When light strikes the semiconductor material,
electrons are excited and move from the valence
band to the conduction band. This creates a
current that flows through the photocell.

Basic Electric Circuit-1
Introduction
• The flashlight is an example of a basic electric circuit
• Flashlight consists like any basic circuit: source, load (the
bulb) and a switch
• The LOAD is any device through which an electrical
current flows
• The SOURCE is the device which furnishes the electrical
energy used by the load.
• The SWITCH, permits control of the electrical device

introduction con’t.
• The schematic diagram is a "picture" of the circuit
which uses symbols to represent the circuit
components
• physically large or complex circuits can be shown
on a relatively small diagram

introduction con’t…
• The following figure shows the circuit symbols
Symbols commonly used in electricity

introduction con’t…
The schematic in below figure shows a flashlight:

• introduction con’t…
Figure right Basic
flashlight schematic.
Q1. In figure right what
part of the circuit is
(a) load and
(b) source?
Q2. What happens to the path
for current when S1 is open as shown
in figure (A)?

Circuit Laws-1
a. Ohm’s Laws:
• Ohm’s law states that, current is inversely
proportional to resistance and expressed as an
equation:

Circuit Laws-3
Kirchoff’s First `Law:
• In a parallel circuit, the algebraic sum of the
currents entering a point is equal to leaving that
point.
• This law expresses in terms of the below
equation:
IT – I1 – I2 – I3 = 0 Or IT = I1 + I2 + I3

Circuit Laws-4
Kirchhoff’s First Law

Circuit Laws-2
b. Kirchhoff’s Voltage Laws:
• In a series circuit, the algebraic sum of the voltage
drops in that circuit must be equal to the source
voltage
• Kirchhoff’s second law for series voltage drops
can be expressed algebraically as follows:
ET - V1 - V2 -V3 = 0, Or ET = V1 + V2 + V3

Circuit Laws-5
Kirchhoff’s Second Law

Series DC Circuits-2
• For resistors in a series, the total resistance of the
circuit is equal to the sum of the individual
resistors.
• The basic formula is:
• In the below series circuit, here is a 12-volt DC
source in series with two resistors, R1 = 10Ω and
R2 = 30Ω.

• If RT of the circuit reduce in half of its original
value. The effects on the total current are:
• The current through
a series circuit will
always be the same
through each element and at any point.
• Ohm’s law describes a relationship between the
variables of voltage, current, and resistance.

Voltage Drops and Further Application of Ohm’s
Law:
• Voltage drop is the loss in electrical pressure or
emf caused by forcing electrons through a
resistor.
• as there are two resistors in the example, they
have separate voltage drops.

• In Figure the values
used to illustrate the ide
of voltage drop are:
Example of three resistors in series.

• The drop for each
resistor is the product
of each resistance
and the total current
in the circuit
• The source voltage is:

Parallel DC Circuits-1
• Number of circuits are connected across the
same voltage source is parallel circuit
• The difference between the series and parallel
circuit is that more than one path in the parallel
circuit.
• Each of these parallel paths is called a branch.

• Current flowing out of the
source divides at point A
and goes through R1& R2.
• Voltage Drops is the
Voltage across any
branch is equal to the
voltage across all of the
other branches
Basic parallel circuit.

• The total resistance of a parallel circuit is less
than the value of the smallest resistor in the circuit
• The amount of current in each resistor will vary
according to its individual resistance.
• The total current of the circuit is the sum of the
current in all branches

• The formula for the total parallel resistance is:
• The general formula for the total parallel
resistance is:

• Any number of resistors in a circuit can be broken down in to
pairs:
• Combining the terms in the denominator and rewriting:
• two resistors in parallel is equal to the product of both resistors
divided by the sum of the two resistors.

• calculate the total resistance:

Series-Parallel DC Circuits-3
The total resistance of the circuit is given as:
Determining total resistance.

• IT can be determined Using Ohm’s law:
• The current through the
parallel branches of R2
and R3 can be calculated:

• using Kirchhoff’s current law, determine I3:

Power Calculation in DC Circuits-3
• Energy can neither be created nor destroyed but
merely changed into other forms.
• Electrical Power:
P = V x I =watts = volts x amps
V = IR , substitute for V,

• Electrical equipment withstand a certain amount of
heat without damage,
• An equipment can consume without damage is its
‘power rating’ or ‘wattage rating’
• The more power consumed by a device the more heat
or light it produces in a given time
• The rating 6V, 12W on a lamp means to a 6V supply,
can develop 12W power intended to work at this
rating.

• power rating of a resistor has a different meaning
from that of a bulb.
• In this case we must always keep below the
stated value.
• Maximum Current
• Therefore, this is the maximum current to avoid
damage to the resistor,

• Example:
Calculate the power dissipated
in a 10kohm resistor with a 5mA
current through the resistor.
• Therefore power dissipated in the resistor is
250mW.

The total resistance in the circuit is 4Ω and the circuit
current is 3A
• The power developed in the load is 9 watts
Maximum Power Transfer

Lesson summary
• The flashlight is an example of a basic electric circuit and
consists of source, load (the bulb) and a switch.
• The schematic diagram is a "picture" of the circuit which
uses symbols to represent the circuit components.
• Voltage drop is the loss in electrical pressure or emf
caused by forcing electrons through a resistor.

Lesson 8:
Capacitance/Capacitors

LESSON 9
Magnetism and
Electromagnetism

Objectives
 Describe the properties of a magnet and various types of
magnetic materials.
 Describe the BH curve, the significance of a hysteresis
loop, the effect of eddy currents and the methods used to
reduce them.
 Identify the precautions for the care and storage of
magnets.
PPT 2.2 ET-AV01: Electrical Fundamentals Rev No. 0

Properties of A Magnet-1
• Magnetism
• is an invisible force and the nature of it has not been
fully determined
• It can best be described by the effects it produces.
• Examination of a simple bar magnet discloses some
basic characteristics of all magnets.

Magnetic field around magnets

• If the magnet is
suspended to swing freely,
• it will align itself with the
earth’s magnetic poles.
• Since the earth is a giant
magnet,
• its poles attract the ends of
the magnet.

• Each molecule in a
magnet is itself a tiny
magnet.
• In an un-magnetized
state,
• the molecules are
arranged at random
throughout the iron bar.
Un-magnetized Magnetized

• The magnetic force or field around a
magnet can best be demonstrated
using bar magnet and iron filings .
• A sheet of transparent material
placed over a bar magnet and
• iron filings are sprinkled slowly
on this transparent shield.
• The iron filings will arrange
themselves forming a field lines
from the north to south.
Tracing out a
magnetic field
with iron
filings.

• Like poles repel each
other
• because the lines of force
will not cross.
• Reversing the position of
one of the magnets,
• unlike poles attract each
other as shown below.
Like poles repel
Like poles Attract

Magnetization & Demagnetization-1
• Bringing a magnet into contact with a ferromagnetic
material can produce magnets
• Passing a current through a coil wound around it can
magnetize an iron bar.
 Safety precautions during handling of a magnet
1. Precautions should be taken during a
storage of magnets
2. Rough handling or hammering can cause
demagnetization.

Magnetization & Demagnetization-2
3. Heat can cause de-magnetization. Keep
magnets cool.
4. A dc current, or magnetic field caused by
ac, can de-magnetize.
5. Magnets should be guarded against such
effects.

Types of Magnetic Materials-1
• Ferromagnetic materials can be easily magnetized
and exhibit strong magnetic properties
• This group can be further subdivided into “Hard” and
“Soft” magnetic materials.
• Hard magnetic materials are more difficult to
magnetize
• But it retain most of their magnetism when the
magnetising force is removed.

Types of hard magnetic material:
1. Ticonal – Iron-Cobalt / Nickel / Aluminium /
Titanium & Copper.
2. Alnico – Iron – Nickel / Cobalt & Aluminium
• The above materials are used for permanent
magnets.

• Soft magnetic materials can be magnetized very
easily,
• It loose most of the magnetism when the
magnetising force is removed.
• Stalloy & Mumetal are examples of soft magnetic
materials
• These are Paramagnetic Materials
used for temporary magnets.

• Diamagnetic Materials oppose the magnetising
force
• If placed in a magnetic field, they will decrease its
strength.
• Diamagnetic Materials are: Copper / Brass /
Bronze / Mercury / Bismuth.

Precautions For Handling and Storage of Magnets-2
Handling:
• Keep electronic appliances and magnetic data
media away from magnetic materials
• The highest admissible working temperature is
between 120°C and 350°C.
• Do not use these magnets untested in different
media.

Lesson 9.2:
Electromagnets

Electromagnets-2
• The electrons moving through the wire creates the
magnetic field around the conductor.
• The greater the current flow, and the greater the
magnetic field.
• Figure below illustrates the magnetic field around a
current carrying wire.

Electromagnets-3
• A series of concentric circles
around the conductor represent
the field,
• In a coil made from loops of a
conductor,
• many of the lines of force
are dissipated between the
loops of the coil.
Magnetic field formed around a
conductor

Electromagnets-4
• By placing a soft iron bar inside
the coil,
• The lines of force will be
concentrated in the center of
the coil
• This combination of an iron
core in a coil of wire loops, or
turns, is called an
electromagnet.
Electromagnet

Factors Affecting Field Strength In Electromagnets-1
 Faraday’s Law :
• When a conductor cuts or is cut by magnetic lines
of flux, an emf will be induced in that conductor.
Factors Affecting the Induced EMF:
1. The galvanometer deflection increases
directly as the velocity of relative motion of
the coil and the magnet.

2. When the magnet is removed from the coil,
the galvanometer needle reads zero
3. Inserting the North Pole of the magnet gives
an opposite deflection to that of the South
Pole is inserted.
4. The use of a more powerful magnet gives a
greater deflection and more lines of flux

5. If the coil is replaced by one having a
greater number of turns a greater deflection
is obtained
• When the magnetic flux through the coil is made
to vary, an emf is induced in the coil
• The magnitude of the induced emf is proportional
to the rate of change of flux.

Construction And Application Of Electromagnets-2
• A core of ferromagnetic
material like iron serves to
increase the magnetic field
created
A simple electromagnet consisting of a coil of
insulated wire wrapped around an iron core.

Lesson Summary
• The electrons moving through the wire creates the
magnetic field around the conductor
• The direction of the magnetic field depends on the
direction of the current.
• When a conductor cuts or is cut by magnetic lines
of flux, an emf will be induced in that conductor

Lesson 10:
Inductance/Inductors

Lesson 11
DC Motor/ Generator Theory

Introduction
• DC motors and generators are essential
components of aircraft electrical systems.
• They convert mechanical energy into electrical
energy or vice versa.
• We will discuss the basic theory of DC motors and
generators, as well as their construction and
purpose in aircraft.

Basic generator theory
• A DC generator is a machine that converts
mechanical energy into electrical energy.
• It does this by rotating a conductor in a magnetic
field.

• The movement of the conductor through the
magnetic field induces an electric current in the
conductor.

Construction and purpose of typical DC generator
• Armature: The armature is the rotating part of the
generator.
• Field winding: The field winding is the stationary
part of the generator that creates the magnetic
field.

• Commutator: The commutator is a device that
changes the direction of the current in the
armature winding.
• Brushes: The brushes are conducting blocks that
make contact with the commutator and carry the
current to the load.

Basic DC motor construction and operation
• A DC motor is a
machine that
converts
electrical energy
into mechanical
energy.

Basic DC motor construction and operation
• It does this by passing an electric current through
a conductor in a magnetic field.
• The movement of the conductor through the
magnetic field creates a force that rotates the
conductor.

Change of speed and direction of rotation
• The speed of a DC motor can be changed by
adjusting the voltage applied to the motor or by
changing the strength of the magnetic field.
• The direction of rotation of a DC motor can be
changed by reversing the connection of the
brushes to the commutator.

Summary
• DC motors and generators are essential
components of aircraft electrical systems.
• They convert mechanical energy into electrical
energy or vice versa.
• This presentation has discussed the basic theory
of DC motors and generators, as well as their
construction and purpose in aircraft.

Lesson 12
Transformer
PPT1.17 ET-AV01:Electrical Fundamentals Rev No.0

Transformers-1
• A TRANSFORMER is a device that transfers
electrical energy from one circuit to another by
electromagnetic induction.
• The electrical energy is transferred without a
change in frequency, but may involve changes in
magnitudes of voltage and current.
• A changing current in the primary windings
creates a changing magnetic field in it

Transformers-2
• Transformer symbol

Transformers-3
• magnetic field induces a changing voltage in the
secondary windings
• By connecting a load in series with the secondary
windings, current flows in the transformer

Construction & Operation of Transformer-1
 Core type
• A core type has ‘u’ shaped and either ‘i’ or ‘l’
shaped laminations , staggered to provide a single
circular magnetic circuit
• The windings may be wound on one limb or split
between the two

 Transformers

Transformers

The principle of the transformer

transformer parts and it parameters

• BASIC OPERATION OF A TRANSFORMER

 Shell type core
• The laminations of
a shell type core are
usually ‘t’ and ‘u’
shaped, when assembled to
produce a three-limbed
core

Symbol, Turns Ratio & Polarity Markings Circuit symbols-1
• The two dots are used
to indicate the phase
relationship between
the two windings
• the terminals marked
with a dot are always
in phase with each
other Transformer dot codes
180◦phase change
No phase change
Voltage input Voltage output
Primary winding
Secon.winding

• The core material is determined by the frequency of
the supply on which the transformer is to be operated
• Three lines drawn between the primary and
secondary windings indicate it has a laminated iron
core.
• The below transformer has two secondary windings,
• the dot notation indicates that these two windings are
wound in opposite directions

Laminated core type

• When there are no lines
between the two windings,
the transformer is air cored
• This type is used on very
high frequencies (VHF) and
above.
Schematic symbol for an iron-core power
transformer.

 Schematic symbols for transformers

Primary & Secondary Voltage & Currents-1
 Turns and voltage ratios
• When a load is connected across the secondary
winding, current flows through it and through the load

 Turns and current ratios

Transformer Losses & Efficiency-2
• Transformer losses are very small it is about 98%
efficiency
• losses can be divided into three groups;
1. Iron or core losses.
2. Copper losses.
3. Flux leakage losses.

Transformer Losses & Efficiency-3
• Iron or core losses are divided into two groups;
hysteresis and eddy current.
• Copper losses are the i2r losses in the windings
• Copper losses are dependent on the primary and
secondary currents

Transformer Under load and No-load-1
 No-load condition
• Losses in a primary winding of practical transformer are
due to :
1. resistance,
2. hysteresis and
3. eddy currents
•The secondary voltage is anti-phase with
respect to the applied voltage
•due to the large reactance of the primary
circuit, the primary current is very small

• If a transformer is
operated at a lower
than rated frequency,
the XL will be small
No-load condition

 Load condition
• The ampere turns in the primary and secondary
are equal:

Transformer Applications-1
 Power Transformer
• As the transformer does not add electricity, total
amount of energy in a circuit is the same
• The transmission of power over long distances is
accomplished by using transformers

 Instrument Transformers
• It is used in AC system to measure V,I,P,PF(cos )
and F.
• also used with protective relays for protection of
power system.
• it is used to step down the AC System voltage
and current

a. Voltage Transformer
• It is used to step down
voltage to safe value
for measuring purpose

b. Current Transformer
• It is used in AC power
supply systems to
sense generator line
current for circuit
protection
• The sides of all current transformers are marked
“H1” and “H2” on the unit base.

Lesson summary-1
• A TRANSFORMER is a device that transfers
electrical energy from one circuit to another by
electromagnetic induction.
• At any instant the flux, Φ, in the transformer core
is given by the equation:
• Transformers are important electrical-electrical
energy conversion components

Lesson summary-2
• Transformers are magnetically coupled coils
• Ratio of turns from primary to secondary is the
“turns ratio”. Side with greater number of turns
has higher voltage, but lower current
• Ideal transformers: Power in = Power out

Introduction
• What is an AC generator?
• How does an AC generator work?
• What are the different types of AC generators
used in aircraft?
• What are the components of an AC generator?

Large Aircraft AC Generators
typical Aircraft electrical power location
PPT3.53 ET-AV04:Aircraft Electrical Systems-I Rev No.0

Basic Principles of AC Generation
• In an AC generator,
electricity is produce by
using the concept of
Faraday’s Law of
electromagnetic induction
which states that:

The working principle of an AC generator
• The principle of electromagnetic induction
• The rotation of the armature
• The generation of alternating current

The different types of AC generators used in aircraft
• Three-phase generators
• Permanent magnet generators
• Brushless generators

components of an AC generator
• Armature
• Field winding
• Slip rings
• Brushes

AMT AV801 M-3 Electrical Fundamentals Biruke.pptx

AMT AV801 M-3 Electrical Fundamentals Biruke.pptx

Recommended

Recommended

More Related Content

Similar to AMT AV801 M-3 Electrical Fundamentals Biruke.pptx

Similar to AMT AV801 M-3 Electrical Fundamentals Biruke.pptx (20)

More from seidnegash1

More from seidnegash1 (7)

Recently uploaded

Recently uploaded (20)

AMT AV801 M-3 Electrical Fundamentals Biruke.pptx