fundamental electricity

8/14/2019 Fundamental Electricity

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Fundamentals of Electricity

Azhar Khairuddin


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The natureof electricity Current, voltage,power, energy

DC: AC:

frequency, polyphase

Real, reactive,and apparent power:

power factor

An overall perspective

of Electrical Engineering

Fundamentals of

Electricity


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Fundamentals of Electricity

- The Nature of Electricity

Electrical Engineering discipline that deals with the study and application of

electricity, electronics, and magnetism

concerned with using electricity to transmit energy

Electricity property of matter that results from the presence or movement

ofelectric charge. Together with magnetism, it constituteselectromagnetism

responsible for many well-known phenomena such aslightning, electric field, electric current

put to use in industrial applications such as electronics andelectric power.


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Charge and Electricity

Charge electrical property of

atomic particles of which

matter consists, measured in

coulombs (C)

Atom consists of electrons,

protons, and neutrons.

Charge of an electron = 1.602

x 10-19 C


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Electric Current

Rate at which charges flow past a

point in a closed loop (circuit)

consisting of a potential source

Measured in ampere (unit is A)

1 ampere = 1 coulomb / 1 second

Conventional direction from

positive to negative terminal of

the voltage source actual

direction is according to electron

flow (negative to positive)


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Voltage

The difference of

electrical potential

between two points of an

electrical network (in

Volt, V)

A measure of the ability of

an electric field to cause

an electric current in anelectrical conductor

(circuit)


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Hydraulic Analogy

Water circulating in apipe, driven by pump asan analogy of an electrical

circuit Fluid pressure differencebetween two pointscorrespond to potential

(voltage) difference With pressure difference

between two points, then

water flowing from thefirst point to the secondcan do work

Similarly with potential

difference, electron canflow current do the work


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Ohms Law

Potential difference between two

points along a connected path

and the current flowing through

it are proportional at a fixed

temperature

V= IR

V is the potential difference,

I is the current,

R

is a resistance of conductor.

Georg Simon Ohm

German physicist

(17871854)


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Resistance of the conductor

Resistance

Also varies with

temperature

frequency Spiralling of

conductor

AR

l=


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Power and Energy

Work done to move water is equal to the pressure

multiplied by the volume of water moved.

Similarly, in an electrical circuit, the work done to

move electrons is equal to 'electrical pressure' (an

old term for voltage) multiplied by the quantity of

electrical charge moved

Power = Voltage x Current (P = VI) , in WattWork done (Energy) = Power x time (Ws)

Normally in EE, Energy is in kWh


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Direct Current vs Alternating Current

DC

constant flow of charge(current) from high to lowpotential

AC

Current whose magnitude and

direction vary cyclically The usual waveform of AC is

sine wave -the most efficienttransmission of electricalenergy


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Alternating Current

Maximum Value, Imax

Root mean square

(Effective) value, Irms

Period, T

Frequency, f

2maxII rms =

T

1f =


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DC vs AC Generation

DC generation is from Battery

Rectifier

DC Generator

AC generation is from AC Generator


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Three Phase AC System

Waveform same in

magnitude and shape

but different in phase

Phase difference is120o

Connection can be

either delta or wye


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Power

In power calculation, normally, rms (effective) values are used

In DC circuit,

Resistance - the only element considered in DC circuitP = VI (a constant) , in Watt (W)

In AC circuit,v and i are varying against time

Resistance, inductance and capacitance can affect the AC system

Resistance consume power (real and active power)

Inductance takes power from and returns it to source

Capacitance produces power and takes the same power backReactive power relates to inductance and capacitance


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Power Factor

Cos of the angle between voltage and current

For purely resistive circuit, voltage is in phase with current

Pf = 1 since cos = 0

For inductive circuit, current lags voltage by an angle

Pf < 1 (lagging) since cos between 0 and 90o

For capacitive circuit, current leads voltage by an angle

Pf < 1 (leading) since cos between 0 and 90o


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Real power is the power

measured by TNB meterP = Vrms x Irms x pf

Reactive Power

produced by capacitance ortaken by inductance

Q = sqrt (S2 P2)

Apparent power Sum (in complex no. form) of P

and Q

Rating of power systemcomponents such as generator,transformers, etc

S = Vrms x Irms


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Power Factor Correction

TNB penalise for low

pf of less than 0.85

To avoid penalty,

large user may

improve pf by

Installing capacitor

Use synchronousmotor


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Overall Perspective of EE Research in electricity was

intensified in the 19th century Georg Ohm in 1827 proposed Ohms

Law

Micheal Faraday discoveredelectromagnetic induction in 1831

James Clark Maxwell published aunified theory of electricity andmagnetism in 1873

During these years, the study ofelectricity was largely considered to

be a subfield of physic

In the late 19th century thatuniversities started to offer degrees

in electrical engineering.

Ohm

Faraday

Maxwell


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The Darmstadt University of Technology, Germany

founded the first chair and the first faculty of electricalengineering in 1882

introduced the world's first courses of study in electrical

engineering in 1883

University College London, UKniversity College London, UK

founded the first chair of electrical engineering in 1885

University of Missouri, USA established the first department of electrical engineering

in the US in 1886


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In 1882, Thomas Alva Edison

switched on the world's first large-

scale electrical supply network that

provided 110 volts DC to fifty-nine

customers in lower Manhattan

Developed incandecent lamp and

telegraphy

In 1887, Nikola Tesla filed a number

of patents related to a competing formof AC power distribution

Also contributed on the development of

induction motor and polyphase system

Edison

Tesla


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Educating EE

EE possess a degree in Electrical Engineering

The length of study usually four or five years

The degree covers physics, mathematics, projectmanagement, and specific topics in ElectricalEngineering

Some electrical engineers also choose to pursue apostgraduate degree such as a Master or PhD in

EE

Info : www.fke.utm.my


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Practising EE

In most countries, a Bachelor's degree in engineeringrepresents the first step towards profesionalcertification and the degree program itself is certifiedby a professional body

After completing a certified degree program theengineer must satisfy a range of requirements(including work experience requirements) before beingcertified

Once certified the engineer is designated the title ofProfessional Engineer

Info : www.bem.org.my

www.iem.org.my


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The End

fundamental electricity

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