Muhammad Ramlee KamarudinWireless Communication Centre (WCC)

Universiti Teknologi Malaysia

Mechanical and Electrical Systems SKAA 2032

Brief BiodataName : Muhammad Ramlee KamarudinPosition : Associate ProfessorAffiliation : Wireless Communication Centre (WCC) Email Address : ramlee@fke.utm.myOffice Address : Wireless Communication Centre (WCC),

Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia.Room Number : P15a-level 2Phone Number : 07- 5535350 / 019-7007001Personal webpage : muhdramlee.wordpress.comQualification

• PhD: University of Birmingham, UK (Sept 2007)• MSc: University of Birmingham, UK (Sept 2004)• B.Eng: Universiti Teknologi Malaysia (March 2003)

Research Area : Antenna Design

Course Outline

1. Power Supply (AC and DC) 4 hrs1.1 Current, Voltage, Power and their relationships1.2 Single and Three Phase System (star and delta)1.3 Source of Supply, Transmission and Distribution

2. Electrical Machinery (Transformer and Three Phase Induction Motor) 6 hrs2.1 Transformer: Principle of operation and application, Rating, Losses and Efficiency2.2 Induction Motor: Principle of operation and application, Synchronous speed, Rotor speed and sleep, Rating and starting circuits.

Course Outline

3. Electrical Distribution and Wiring 4 hrs3.1 Wiring system, Types and size of cables3.2 Protections and Grounding 3.3 Electrical Load (Estimation)3.4 Substation, Switchboard and Distribution Board3.5 Symbols and Single line diagram

References

1. B. L. Theraja, Electrical Technology2. Hughes, Electrical Technology, 9th Edition3. D. E. Johnson, J.R. Johnson, J.I. Hilburn, Electrical Circuit Analysis, Prentice Hall4. Thomas L. Floyd, Electric Circuits Fundamentals, 5th Edition, Prentice Hall5. P.C. Sen, Principles of Electrical Machines and Power electronics, 2nd Edition John Wiley & Sons 19976. Stephen J. Chapman, Electrical Machinery Fundamentals, 4th Edition McGrawHill 2005 7. Theodore Wildi, Electrical Machines, Drives and Power System, 4th Edition, Prentice Hall

Lecture notes and tutorials will be informed through email

Course Objectives

• To give basic information about electrical principle, electrical machinery, distribution system, wiring and protection

Course Assessment

• Electrical System (50%)– Assignment : 10%– Midterm Test : 15%– Final Exam : 25%

• Mechanical System (50%)• Total: 100%

• Students need to attend 80% of the classes to be in final exam

• Class replacement :Class we missed: 29 Oct (I haven’t been told), 5 Nov (Japan) and 3 Dis (Korea)

Class: 19 Nov, 26 Nov, 10 Dis (Not sure, Melaka), 17 Dis

Replace: 3 Classes….When??

Familiarization With Electricity

Electrical shock!

Electrical Engineering

• Professional engineering discipline that deals with the study and application of electricity, electronics and electromagnetism

• Among subdivisions of electrical engineering are: power, optoelectronics, digital electronics, analog electronics, artificial intelligence, control systems, electronics, signal processing and telecommunications.

Electrical Engineering

Power• This field deals with energy production, energy conversion to

and from electrical form, energy transmission over long distances, and energy distribution to houses and industrial complexes.

Control Systems• This field concern with information gathering from sensors

and the use of electrical energy to control physical process.

Electronics• Electronics is the study and application of materials, devices,

and circuits used in amplifying and switching electrical signals.

Electrical Engineering

Telecommunications• Transport information in electrical form. Cellular telephones,

radio, satellite television and the internet are examples of communication systems.

Signal Processing• Is concerned with information-bearing electrical signal. Often,

the objective is to extract useful information from electrical signals derived from sensors. Application are machine vision and robotics.

Basic of Electrical System

• Electricity is a form of energy. We use electricity for various purposes such as:– Lighting, heating, cooling and other domestic

electrical appliances used in home.– Street lighting, flood lighting

of sporting arena, office building lighting, powering PCs

– Running motors, furnaces of various kinds, in industries.

Basic of Electrical System

• Examples of energy source hydro, coal, gas, wind, nuclear and solar

• Electricity can be generated from these sources.

Basic of Electrical System

• Electrical systems permit us to easily transmit energy from a source of supply to a point of application

Basic of Electrical System

1. The source - to provide energy for the electrical system, e.g. Battery, generator, socket outlet2. The load - to absorb the electrical energy supplied by the source, e.g. Lamps, air-cond.3. The transmission system - conducts energy from the source to the load, e.g. Insulated wire4. The control apparatus - permits energy to flow or interrupts the flow, e.g. switch

Basic of Electrical System

Example of Electrical System

Electrical Power Systems

Electrical engineer design systems objective:

To gather, store, process, transport, and present information

To distribute, store, and convert energy between various form

Manipulation of energy

Manipulation of information

interdependent

Mechanical and Electrical Systems SKAA 2032

Power Supply (AC and DC)

Power Supply (AC and DC)

• Electricity is the movement of free electrons in a material toward an area of positive (+) charges.

• The conduction of those electrons is determined by the type of material. Some conduct well, while other materials prevent the movement of electrons.

• Electricity can take the form of static electricity, direct current (DC) electricity, or alternating current (AC) electricity.

Power Supply (AC and DC)

• What are free electrons?

• What determines the conduction of electricity?

• What are the different types of electricity?

Free electrons

• All matter is made up of atoms• The basic atom consists of a nucleus surrounded by

electrons going round the nucleus in orbit

• The nucleus consists of:– Protons which are positively charged– Neutrons that have no charge.

• The electrons have a negative (-) electrical charge

Lithium atom

Proton charge= 1.602 x 10-19 Coulomb

Elec. charge= -1.602 x 10-19 Coulomb

Free electrons

• Most electrons are bound in orbit around atoms. • But in many substances, there are electrons that

are not connected to any atom and are roaming freely throughout the material.

• These electrons may have been knocked free in the creation of ions or may be the result of a collision of a high energy particle, such as from radioactive materials or cosmic rays.

Free electrons

• Atoms with an excess of electrons are called negative ions and those that are missing electrons in the shells or orbits are called positive ions.

• An electric force field causes particles with opposite charges to attract each other.

• A buildup of opposite charges creates an electric potential.

• Release of the potential energy results in the movement of free electrons, which is called electricity.

Valence electrons

• Valence electrons are the electrons contained in the outermost, or valence, electron shell of an atom.

• Important in determining how an element reacts chemically with other elements.

• The fewer valence electrons an atom holds, the less stable it becomes and the more likely it is to react.

Proton charge= 1.602 x 10-19 Coulomb

Elec. charge= -1.602 x 10-19 Coulomb

Conductors

• Conductors are materials that permit electrons to flow freely from atom to atom and molecule to molecule.

• An object made of a conducting material will permit charge to be transferred across the entire surface of the object

• This relative mobility of electrons within a material is known as electric conductivity.

Conductors

• Solid metals are good conductors of electricity, because electrons are allowed to move freely throughout the material.

• Copper and gold are some of the best conductors of electricity.

• Although iron is a good conductor, iron oxide (rust) is not.

• In the solid state, the atoms of metals are held in place and only vibrate. This allows free electrons to roam about the material.

Semiconductors and Nonconductors

Semiconductors• Has electrical conductivity intermediate to that of a conductor

and an insulator • This behavior is useful in in designing computer chips—the

electrons have limitations to their movement, such as only being allow to move in one direction or in one plane.

Nonconductors/insulators • Prevent the movement of electrons within the material. But they

often do allow electrons and ions to collect on their surfaces. • Examples of nonconductors or electrical insulators are: Plastic,

Rubber, Glass, Most metal oxides (like rust), Air, Oil, Pure, de-ionized water

• Gases are not good conductors of electricity because of the distances between atoms.

Energy bands

Types of electricity

• Common types of electricity are:– static electricity, – direct current (DC) electricity– alternating current (AC) electricity.

Static electricity

• Static electricity refers to the built up electric charge on the surface of objects or excess of electric charge (imbalance) trapped on the surface of an object.

• Charge exchange can happen when any two surfaces come into contact or rubbed.

• When the materials are separated they retain this charge imbalance.

• Since opposite charges attract, there is a tendency for the electrons to attract toward the positive ions.

AC electricity

• Electrons will flow from an area of an excess negative (-) charges to an area of positive (+) charges.

• Alternating current (AC) is when the electrons flow in both directions — AC terminals constantly switch their polarity from (+) to (-) and back again.

• An AC voltage is continually changing between positive (+) and negative (-).

• Electrical power grids that provide electricity to homes and other buildings use AC.

DC electricity

• In direct current (DC, also dc), the flow of electric charge is only in one direction. It may increases or decreases.

• Sources of DC voltage are include cells, batteries and regulated power supply.

• A DC voltage is always positive (or always negative).

Unit Used in Electrical Quantities

• Charge• Force• Work• Electric current• Electrical Potential• Power• Resistance• Conductance

Charge

• The unit of charge is the Coulomb (C).• The coulomb is defined as the quantity of

electricity which flows past a given point in an electric circuit when a current of one ampere is maintained for one second.

• Charge, in coulombs: Q=It– I is the current in ampere – t is the time in seconds

Force

• The unit of force is the newton (N).• One newton is one kilogram meter per second

squared ( kg·m·s-2)• Force, in newton: F=ma

– m is the mass in kg– a is the acceleration in ms-2

Work

• The unit of work or energy is the joule (J)• Joule is defined as the work done or energy

transferred when a force of one newton is exerted through a distance of one meter.

• The work done, in joules: W=Fs– F is the force in newtons– s is the distance in meter

Electric current

• Electric current is the rate of charge flow past a given point in an electric circuit, measured in coulombs/second which is named amperes.

• In most DC electric circuits, it can be assumed that the resistance to current flow is a constant so that the current in the circuit is related to voltage and resistance by Ohm's law.

Electrical potential and e.m.f.

• The unit of electric potential is the volt (V)• The potential difference indicates the flow of

electric current (from high to low) • The potential difference is also called voltage.

Analogy

Electrical potential and e.m.f.

The units of the potential difference is given byVolts = watts/amperes = joules/amperes·second

= joules/coulombs• A device that maintains potential difference between

two points is said to develop and electromotive force (e.m.f.).

Power

• The unit of power is watt (W)• One watt is one joule per second• Power, in watts : P=W/t

– W is the work done– t is the time in second

• DC electrical power, in watts: P=VI– V is the voltage across the load– I is the current flows through the load

• Energy, in joules, W=Pt

Resistance

• The unit of electric resistance is the ohm (Ω)• It is defined as the property of a substance due

to which it opposes the flow of electricity (or electrons) through it.

• Resistivity, in ohms·meter (Ω·m) : ρ=AR/l– A is the cross section of the conductor– L is the length of the conductor

• Note that the resistance is dependent on the nature of the material and also the temperature.

Resistance

• R = 0 Ω – short circuit (large current flow)• R = Ω – open circuit (no current flow)

• The reciprocal of resistance is called conductance and is measured in siemens (S).

• Conductance, in siemens: G=1/R

Open circuit Short circuit

Ohm's Law for Electrical Circuits

• Ohm's Law states that in a simple electrical circuit, the voltage equals the electrical current times the resistance.

where:V is the voltage in volts I is the current in amperes or amps R is the resistance in ohms IR is I times R

V = IR

Example

• How many amperes of current are in the circuit below?

VsR100 V 20 Ω

I = Vs

R= Using Ohm’s law:

100 V

20 Ω= 5 A

Examples

1. An electric bulb uses 0.5 A of current with voltage generated being 120 V. Determine the value of resistance.

2. If a current of 0.5 A flows through resistor of 15 Ω, calculate the voltage drop across the resistor.

1. Ans; R = V/I = 120/0.5 = 240 Ω 2. Ans; V = IR = 0.5 x 15 = 7.5 V

Examples

3. (i) For the circuit shown, determine current flowing and power absorbed by the resistor if the resistance is 1 kΩ and voltage across it is 10 V(ii) If the current flowing through the circuit is 3A and power absorbed is 72 W, determine the resistor value and voltage across it.

V R

I

Vs

+

-

+

-

DC Power

• The electric power in watts represents the rate at which energy is converted from the electrical energy of the moving charges to some other form, e.g., heat, mechanical energy, or energy stored in electric fields or magnetic fields.

• For a resistor in a DC circuit, the power is given by the product of applied voltage and the electric current :

Power (watts) = Voltage (volts) x Current (amperes)

P = VI

DC Power

• Although the unit of energy is the joule (W=Pt), when dealing with large amounts of energy, the unit used is the kilowatt hour (kWh) where:

1kWh = 1000 watt hour = 1000 X 3600 wat seconds (or joules) = 3 600 000 J

Electricity Bill = Electricity (kWh) x tariff rates (sen/kWh)

Calculating your electric bill

Computer : 500 watts (12 hours usage)

TV : 400 watts (5 hours usage)

Lighting : 3 units x 15 watt = 45 watts (6 hours usage)

Others : 100 watts (2 hours usage)

Power consumed :

(500 x 12) + (400 x 5) + (45 x 6) + (100 x 2) = 8470 wh = 8.47kWh

Electricity bill per month :

8.47 kWh x RM 0.218/kWh x 30 = RM 55.50

Summary of terms, units and symbols