Fee 1

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Prepared By :

D. R. Mehta

(B. E., M. E., GATE Qualified)

Lecturer (Electrical

Engg

. Dept.)

B. S. Patel Polytechnic,

Ganpat

Vidyanagar

,

Kherva

-

Mehsana

For Students & Staff

To get this complete presentation, send the e-mail on the

following address with your complete details;

[email protected]

This presentation is completely based on the FEE-text bookwritten by D. R. Mehta & T. R. Patel, published by Nirav

Prakashan.

For better understanding this presentation, you can purchasethe FEE Text Book as mention above from neareststationary shop or directly from main office of Nirav

Prakashan, at Ahmedabad.

Fundamentals

of

Electrical Engineering

1

Fundamentals of Electrical Engineering
mailto:[email protected]:[email protected]:[email protected]

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2

Fundamentals of Electrical Engineering

Chapter-1 Fundamentals of Electric and Magnetic Circuit

Chapter-2 Electromagnetic Induction

Chapter-3 A.C. Fundamentals

Chapter-8 Protection & Utilization of Electrical Power

Index

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33

Prepared By :

D. R. Mehta

(B. E., M. E., GATE Qualified)

Lecturer (Electrical

Engg

. Dept.)


Ganpat

Vidyanagar

,

Kherva

-

Mehsana

Chapter 1

Fundamentals of Electric &

Magnetic Circuits

Chapter 1Fundamentals of Electric & Magnetic Circuits

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4

EMF Electromotive Force

Emf (E or V) : The electric effort required to drift free electron in one

particular direction in a conductor is known as EMF.Its full name is Electromotive Force.

V is EMF or voltage.

Its unit is volt.

Current

Current (I) : The rate of flow of charge In any electric circuit is known

as electric current.The free electrons are responsible for the flow of the current.

Its unit is Ampere or Coulombs/sec.

It is denoted by I.

Resistance

Resistance (R) : The property of the conducting material to

oppose the flow of the current flowing through it is known asresistance.

It is denoted by R. Its unit is Ohm ().

It can be written as;

where V = Voltage in volt,

I = Current in Amp.,

= Resisitivity,

l = Length of Conductor,

a = Area of Conductor in m2

.

a

lRor

I

VR


V

I R

4

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5

Potential Difference

Potential Difference : The voltage difference between any two

given points in the electric circuit is known as Potential Difference(P.D.).

The potential difference between point A and B is VAB.

The potential difference between point B and C is VBC.

Its unit is volt.

It is denoted by V.


V

I

R1 R2A B C

VAB VBC

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6

PowerPower (P) : The rate at which the electric work is done in any electric

circuit is known as electric power.

Its unit is Joule/sec or watt.

It can written as;

The electric power can also be expressed as;

P = VI = I2R = watt

wattVIPjoulet

WP or

EnergyEnergy : The power consumed in any electric circuit over a particular

time is known as the electric energy.

Its unit is KWh.


Energy = Power Time

Energy = = P t KWhr

The power must be in KW and time must be in Hour.

It is also known as the Unit.


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EMF & Potential DifferenceR1 & R2 = Two resistor connected

in series

S= Switch

V = Voltage or EMF

R1 R2

S

V

When the switch S is closed, the free electrons flow from the

circuit. It is nothing but the current I.

The electric effort required to flow the electric current from the

circuit is known as EMF. In the circuit, V is the EMF.

I

I

Due to this electric current I, the voltage drop occurs across the

resistance R1 (between point A & B) & resistance R2 (between point B & C.

These voltage drops are known as potential difference.

The potential difference between point A & B is known as VAB.

The potential difference between point B & C is known as VBC.

VAB VBC

A B C


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8

Factors Affecting ResistanceAs we know, the resistance of any conductor can be given by;

a

lR where = Resistivity,

l = Length of Conductor,a = Area of Conductor in m2.

Factors affecting resistance

1. Length of Conductor2. Cross-sectional area of conductor3. Types of material4. Temperature : The resistance of a conductor also depends on

the temperature. As the temperature increase, the resistanceof a conducting material also increases & vice-versa.

In general, without considering the temperature effect;

alR

1. Length of Conductor

2. Cross Sectional Area of Conductor

3. Types of Material4. Temperature


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This Constant is Known as Resistance.

It can be denoted by R.

Its unit is ohm ().

9

Ohms LawOhms Law : The ratio of voltage applied (V) to any electric circuit

and the current flowing through the same circuit (I) is constant,

assuming temperature remains constant.

V = Applied Voltage,

I = Current

R = Resistance,

I

VR

Ohm law can be written as;

Limitations ofOhms Law :

1. This law is not applicable to non-linear devices or

semiconductor devices such as diode, zener diodes, voltage

regulators etc.2. This law does not count the effect of change in temperature.


V

I R

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10

Magnetic FieldDefinition : The surrounding area of the magnet, in which the

influence of the magnet can be experienced or detected is known as the

Magnetic Field.

This magnetic field is represented by the Magnetic Lines of Force.

The direction of these lines of force is always from N-pole to S-pole,

external to the magnet.

N S

N to S

N to S

S to N

Magnetic Field of Permanent Magnet

Magnet


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11

Magnetic FieldMagnetic Field of Current

Carrying Conductor

V

R

SBy applying the Right hand rule

or thumb rule, the direction of

magnetic field of current carrying

conductor can be found.

Right

Hand

Rule

The direction of magnetic field is

clockwise.


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12

Right Hand RuleThe direction of the magnetic field produced by the current carrying

conductor can be found by Right Hand Rule.

A B

Rule : Hold the current

carrying conductor in the

right hand and place the

thumb in the direction ofthe current flowing

through the conductor

then the curled fingers

shows the direction of the

magnetic field.

1. Conductor AB of length l mt.

2. Direction of current from A to B

3. Applying right hand rule4. Direction of magnetic field is clockwise


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13

Cork Screw Rule

Conductor Conductor

Rule : Ifthe direction of the advancement of the screw is the direction of

the current flowing through the conductor then the direction in which the

screw is rotated, is the direction of the magnetic field.

The direction of the magnetic field produced by the current carrying

conductor can be found by Right Hand Rule.


Direction of

CurrentDirection of

Current

Direction of

Magnetic

Field

Direction of

Magnetic

Field

Direction of

Advancement

Direction of

Advancement

Direction of

Rotation

of Screw

Direction of

Rotation

of Screw

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14

Magnetic CircuitWhen a current is passed through a coil a magnetic field is

generated


Iron Core or ring made from silicon steel material having

cross sectional area of A m2

Coil having N turns wound on

the core.

A m2

Current I flowing through circuit

I

I

Magnetic field produced in the Iron Core

Leakage Flux

Iron Core

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15

MMF Magneto-Motive ForceAs in the electric circuit, the emf is necessary to move the electrons

or pass the current, same way in the magnetic circuit, the mmf is

necessary to establish the magnetic flux.

It can be defined as the multiplication of the number of turns of the

coil and the current flowing through the coil.

It is denoted by Fm.

Fm (mmf) = IN

Its unit is Ampere Turns or AT.

Magnetic Field Strength or Magnetic Field IntensityDefinition : The magnetic field strength is defined as the magneto

motive force per unit length of the magnetic flux path.

It is denoted by H.

Its unit is AT/m.It can be written as;

mATH /

l

MMF


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16

PermeabilityDefinition : The property of the magnetic material to allow for the

production of the magnetic flux in it is known as permeability.

It is denoted by .Its unit is Henry/m.

= 0r

where,

= Absolute permeability of the magnetic material

0 = Permeability of air or vacuum.= 4 10-7

r = Relative permeability of the magnetic material

w.r.t. to air or vacuum.

The relative permeability of the air or vacuum is 1.

Absolute PermeabilityDefinition : In particular medium other than vacuum or air, the ratio

of the flux density B to the magnetic field strength H required to

produce the flux density is known as absolute permeability.

It is denoted by .Its unit is Henry/m.


And B = H

H

B

Permeability of Air or VacuumDefinition : If the magnetic material Is placed in the vacuum or air

then the ratio of the flux density B to the magnetic field strength H

required to produce the flux density is known as permeability of free

space or vacuum.It is denoted by 0.

Its unit is Henry/m.


0= 4 10-7 H/m

mHH

B/0

Relative PermeabilityDefinition : Under the influence of the same magnetic field strength,

the ratio of the flux density produced in a medium other than the

vacuum or air to the flux density produced in the vacuum or air is

known as relative permeability.It is denoted by .

It is unit less.


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17

Magnetic Flux & Flux DensityMagnetic Flux : The total number of magnetic force line exists in the

particular magnetic field is known as magnetic flux.

It is denoted by .

Its unit is Weber.

Flux Density : The flux density is defined as the flux passing per unit

cross sectional area through a plane perpendicular to the direction of

the magnetic flux.

It is denoted by B.Its unit is Wb/m2 or Tesla.


It can also be written as;B = 0rH

2Wb/mArea

FluxB

A


ReluctanceDefinition : The property of the magnetic material to oppose the

production of the magnetic flux in it is known as the Reluctance.

The ratio of the magneto motive force to the flux produced in the

magnetic material is known as Reluctance.It is similar to the resistance in the electric circuit.

It is denoted by S.

Its unit is AT/wb.


AT/wbIN

Flux

MMFS

AT/wb

A

lS

0 r

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18

Leakage Flux and Leakage Factor

Useful Flux

Leakage Flux

Assume,

T = Total flux produced by the magnetic circuit

U = Useful flux

L = Leakage flux

The ratio of the totalflux to the useful flux is

known as Leakage

Factor or Hopkinsons

Leakage Co-efficient.

It is denoted by .

For the electrical

machines, the value of

is usually about 1.15

to 1.25.

u

T

FluxUseful

FluxTotal

Airgap


FringingDefinition : The tendency of the useful

flux to spread outward when passing

through the air gap is known as

fringing.

Fringing

I

I

h

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Sr. No. Electric Circuit Magnetic Circuit

1 It is defined as the closed path for

electric current.

It is defined as the closed path for

magnetic flux.

2 Electromotive force (EMF).

Unit volt.

Magneto motive Force (MMF).

Unit AT.

3 Resistance Reluctance

4 Resistivity Reluctivity

5 Conductance = 1/Resistance Permeance = 1/Reluctance

6 Conductivity = 1/Resistivity Permeability = 1/Reluctivity

7 Current Flux

8 Current Density Flux Density

9 Electric Field Intensity Magnetic Field Intensity

AR

EMFI

Sr. No. Electric Circuit Magnetic Circuit

1 In the electric circuit, the current flows

actually.

In the magnetic circuit, the flux does

not flow actually.

2 The resistivity of the material is

approximately constant.

The permeability of the material varies

with magnetic field strength.

3 The continuous energy is required to

maintain the flow of current.

Once the flux is set up, the continuous

energy does not require to maintaining

it.

4 The current increases as the emf

increases.

The flux remains constant after

saturation and it does not increase withincrease in mmf.

Dissimilarities

19


Similarities

a

lR AT/wb

A

lS

0 r

2/mA

A

I

2/mvolt

d

VE

WbS

MMF

2/mWb

Area

FluxB

2/mAT

l

MMFH

Comparison between Electric Circuit & Magnetic Circuit

h

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2020

Prepared By :

D. R. Mehta (B. E., M. E., GATE Qualified)

Lecturer (Electrical Engg. Dept.)


Ganpat Vidyanagar,

Kherva - Mehsana

Chapter 2

Electromagnetic Induction

Chapter 2Electromagnetic Induction

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Ch 2

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2222


Faradays Law of Electromagnetic Induction

Ch 2

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23

B wb/m2

A V m/s

dx

V m/s

dx

900

V m/s

dx

volt0e

01-Case

voltvBl

dt

dxBlee

902-Case

m

voltSinvBlSin

dt

dxBle

3-Case

A

A A

Definition : The emf induced in the coil due to the physical movement of the

conductor/coil is known as dynamically induced emf.

Dynamically Induced EMF

Explanation

Consider a conductor A of length l meters placed in uniform magnetic field of flux

density B wb /m2 as shown in fig.

Consider the following three cases in which the conductor cut the distance dx with

velocity v m/sec in three different directions.

Case 1

As shown in fig., the conductor cut the distance dx in the direction of magnetic field

in time dt with velocity v m/sec.

In this case, there will be no emf induced in the conductor, as there is no flux cut by

the conductor.

Case 2

As shown in fig., the conductor cut the distance dx in the direction perpendicular to the

magnetic field in time dt with velocity v m/sec. In this case, the flux cut by the

conductor is maximum i.e. B ldx and hence the maximum emf induced in theconductor.

Case - 3

As shown in fig., the conductor cut the distance dx in time dt in the direction makes

the angle with the magnetic field axis.

In this case the flux cut by the conductor is Bldx Sin .


Ch t 2

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Magnetic

Field

S

Direction of

Magnetic Field

ConductorMotion

Motion

24


Flemings Left Hand Rule

Hold your left hand with first finger, middle finger and thumb at right angles.

Put the first finger in direction of magnetic field, middle finger in direction of current

flowing through conductor then the direction of thumb shows the direction of force

acting on the conductor.

Flemings Left Hand Rule

N

A

BMotion

Current

Direction

of Current

Motion

NS

Direction of

Magnetic Field

Motion

A

B

Conductor

Motion

Magnetic

Field

EMF

Flemings Right Hand Rule

Hold your right hand with first finger, middle finger and thumb at right

angles. Put the first finger in direction of magnetic field, thumb in direction of force

then the direction of middle finger shows the direction of emf induced in the

conductor.

Flemings Right Hand Rule

Direction of EMF

Ch t 2

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25


II Es

AlternatingMagnetic Field

EM

COIL A COIL B

Statically Induced EMF

There is no physical motion of conductor but due the alternating waveform of flux,

the flux link with the coil is changed and so, emf induced in the coil.

This emf is known as statically induced emf.

There are two types of statically induced emf;

1. Self induced EMF2. Mutually induced EMF

Self Induced EMF

The emf induced in the coil due to change of its own flux linked with it is

known as self induced emf.

Mutually Induced EMF

The emf induced in one coil due to the change in flux of another coil linked

with it, is known as mutually induced emf.

Lenzs Law

The direction of the statically emf induced in the can be found by using Lenzs

Law. It states that;

The direction of the emf induced in the conductor due to the

electromagnetic induction is such that it oppose the very cause for producing it.

Ch t 2

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26

Fundamentals of Electrical EngineeringChapter 2


Definition : The property of the coil to oppose the instantaneous change in the current

is known as self inductance. It is denoted by L. Its unit is Henry (H).

Self Inductance

Co-efficient of Self Inductance

The co-efficient of the self inductance can be defined in following three ways;

First Method :

The co-efficient of self inductance is defined as the ratio of the flux link with the coil to

the current flowing through the coil.

Third MethodSecond Method

HI

NL

HlANL

2

r0 voltdt

di

L-e

Factors Affecting Co-efficient of Self Inductance

The co-efficient of self inductance is given by

Hl

ANL

2

r0

1. No. of Turns (N)

2. Cross Sectional Area of Magnetic Path (A)

3. Length of Magnetic Path (l)

4. Relative Permeability or Types of Magnetic Material (r)

The factors affecting the co-efficient of self inductance can be summarized as below;Definition : The property of the coil to produce the emf in another coil placed nearer

to them when the current flowing through the first coil changes is known as the mutual

inductance. It is denoted by M. Its unit is Henry (H).

Mutual Inductance

Co-efficient of Self Inductance

The co-efficient of the self inductance can be defined in following three ways;First Method

The co-efficient of self inductance is defined as the ratio of the flux link with the coil to

the current flowing through the coil.

Third MethodSecond Method

HI

NM

1

12

Hl

NANM 21r0 volt

dtdiM-e 1M

Factors Affecting Co-efficient of Mutual Inductance

The co-efficient of mutual inductance is given by;

1. No. of Turns of Both Coil (N1

& N2

)

2. Cross Sectional Area of Magnetic Path (A)

3. Length of Magnetic Path (l)

4. Relative Permeability or Types of Magnetic Material

The factors affecting the co-efficient of mutual inductance can be summarized as

below;

Hl

NANM 21r0

Ch t 2

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27


II

Alternating

Magnetic FieldCOIL A COIL B

II

Alternating

Magnetic Field

BA

Coupling Co-efficient

Consider the magnetically coupled two coils A & B. The coil A has N1 turns

and the coil B has N2 turns.

N1 N2

The coupling co-

efficient given

by;

LL

MK

21

The constant K is known as the co-efficient of coupling. It can be defined as the

ratio of the mutual inductance to the maximum possible value of the self inductance.

For the different values of the K, the couplings between coils are classified as

below;

1. K = 1 : The coils are said to be magnetically tight coupled.2. K =0 : The coils are said to be magnetically isolated from each other.

3. 0 < K < 1 : The coils are said to be magnetically loose coupled.

Ch t 2

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28


I I

COIL A COIL B

I I

BA

e1S

e1M

e2S

e2M

Inductors in Series

There are two ways to connect the inductors in series;

1. Series Addition : In this type of connection, the two coils are connected in

such a way that the magnetic flux produced by them are in additive.

2. Series Opposition : In this type of connection, the two coils are connected

in such a way that the magnetic flux produced by them are in subtractive.

Series Addition

2MLLLwhere,

voltdt

di

L-e

volt2M)L(Ldt

di-e

21

21

Chapter 2

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29


I I

COIL A COIL B

II

B

A

e1S

e1M

e2S

e2M

Series Subtraction

Inductors in Series

2MLLLwhere,

voltdt

diL-e

volt2M)L(Ldt

di-e

21

21

Chapter 2

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30

Fundamentals of Electrical EngineeringChapter 2


Hysteresis Loop

Definition : The relationship between the magnetic field strength (H) and the flux

density (B) for the particular magnetic material drawn on the graph for the complete

one cycle is known as Hysteresis Loop or hysteresis Curve.

O

D

E

F

G

I

J

FLUX DENSITY B

FLUX DENSITY B

MAGNETIC FIELD

STRENGTH H

MAGNETIC FIELD

STRENGTH H

CORCIVE

FORCE

RESIDUAL

FLUX

II

AC

R

Current

O

D

E

F

G

I

D

J

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Prepared By :




Ganpat Vidyanagar,

Kherva - Mehsana

3131

Chapter 3

A.C. FUNDAMENTALS

Chapter 3 A. C. Fundamentals

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33

Advantages of AC System

1. Step up/ Step-down possible using transformer.

2. High voltage transmission possible.

3. Very simple & robust construction of ac motor.

4. Using rectifier, dc can be obtainable very easily.

5. Possible to build up high voltage, low cost generator.


Generation of Alternating EMF

The ac emf can be given by ;

SinV=or vSin wtV=v

SinE=eorSin wtE=e

mm

mm

Term Related to Alternating Waveform

AC Waveform

Time

Voltage

Magnitude & Direction

Changes with Time

1. Cycle : One complete set of positive and

negative values of an alternating quantity is

known as Cycle.

2. Instantaneous Value : The value of the

alternating quantity at any time is known as

instantaneous value. This value can be found by

using following equation;

Sin wtV=v m

3. Maximum Value or Amplitude : The maximum

value of an alternating quantity, positive or

negative, is known as Amplitude or Maximum

Value. It occurs twice in the one complete cycle.

Once in positive half cycle and second in negativehalf cycle.

4. Frequency (f) : The number of cycles / sec. is

called the frequency of an alternating quantity. It

is denoted by f. Its unit is Hz. In India, 50 Hz

frequency is used.

5. Angular Frequency (w) : It is the frequency

expressed in radians per second. It is denoted by

w. It is given by w = 2f.

6. Time Period (T) : The time taken by the

alternating quantity to complete the one

complete cycle is known as the Time Period. It

is also defined as the reciprocal of the

frequency. It is denoted by T. Its unit is sec.

7. RMS Value or Effective Value : Its full name is

Root Mean Square Value. It is equal to the DC

value which when flowing through the given

circuit for given time produces the same heat

which produce by the alternating current when

flowing through the same circuit for the same

time. It can be given by; secf

1=T

8. Average Value or Mean Value : The average

value of the alternating quantity is expressed by

that DC current which transfers across the any

circuit the same charges as it transferred by that

alternating current during the same time.

2

I=I mRMS

9. Form Factor : The ratio of the rms value to the

average value is known as the Form Factor. It is

very useful in voltage generation and instrument

correction factors.

mavg I

2I

10. Peak Factor or Amplitude Factor or Crest

Factor : The ratio of the maximum value to the

rms value is known as the Peak Factor or

Amplitude Factor.

11.1ValueAverage

ValueRMSFactorForm 1.41

ValueRMS

ValueMaximumFactorPeak

11. Phase : The phase of the alternating quantity

may be defined as its position with respect to the

reference axis or reference wave.

12. Phase Difference or Phase Angle : The phase

difference or phase angle of the alternating

quantity may be defined as the angle of the lag

or lead with respect to the reference axis or

reference wave. A A

B

B

B wb/m2

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34


Vector Representation of an Alternating Quantity

Importance of Vector Representation

It is very difficult to represent the alternating quantity in terms of their waveforms

and mathematical equations.

The addition, subtractions of the two alternating quantity is tedious and also time

consuming in terms of their mathematical equations.

Hence, the method which representing the alternating quantity in easier way is

called a Vector Representation of an alternating quantity.

Limitations of Vector Representation

1. As we know, generally the alternating quantity is represented by rms value.

Hence, the projection Y-axis does not give the instantaneous value but it must be

multiplied by to get the instantaneous value.

2. The vector is assumed to be rotated in anti-clockwise direction at constant speed.3. Two alternating quantities of having different frequencies cannot be represented

on the same diagram.

Phase Difference

1st Definition : The phase difference or phase angle of the alternating quantity may be

defined as the angle of the lead or lag with respect to the reference axis or with

respect to the another wave.

2nd Definition : The phase difference may be defined as the difference between the

phases of the two alternating quantities or the angle difference between the two

vector representing the two alternating quantities.Zero Phase DifferenceLagging Phase Difference

Phase

Voltage

E1E2

Phase

Voltage

E1

E2

= 0

Current

AA B

B

C

C

D

D

EE

F

F

G

G

H

H

A

Anti-Clockwise

Direction

O

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35


Addition and Subtraction of Two Alternating Quantities

It is necessary in ac analysis to add or subtract the two or more alternating quantities

with the same frequency but different amplitudes and phases.

The additions o subtraction using waveforms is much tedious and time consuming.

So, it is preferable to add or subtract these quantities by using vectors. This is calledthe Vector Addition or Subtraction of the alternating quantity.

There are two vector methods namely;

1. Graphical Method and

2. Analytical Method

Graphical Methods

In this method, the vector diagram is required to be plotted to the scale.

IR

Im1

Im2

Im3

r 1

2

Step by step procedure to add two or more alternating quantities by using graphical

method of vector addition;

Step 5 The angle made by the resultant vector with respect to the reference is the

phase of the resultant quantity.

Step 1 Choose one of the suitable vector as a reference vector and draw it on the X

axis. Now, all other vectors to be added having their own phases.Step 2 Draw the remaining vectors one after another, considering their individual

phases.Step 3 Join the last point with the origin to complete the vector polygon.Step 4 The length of this vector from origin to last point represents maximum value

of the resultant quantity

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Step by step procedure to add two or more alternating quantities by using analytical

method of vector addition.


Analytical Methods

36

1. Express all the vectors in rectangular form.2. Find X component (real component) and Y component (imaginary component)

of all the quantities.

3. Add all X components and Y components algebraically to obtain the resultant X

component and Y component.4. The magnitude of the resultant vector can be obtained using;5. The phase of the resultant vector can be obtained by;

22 YXResultant XYtan 1

Mathematical Representation of an Alternating Quantity or Vector

Let, the current vector,

Now, this vector can be represented mathematically by four ways;

1. Rectangular Co-ordinate system

2. Polar Co-ordinate System

3. Trigonometric Co-ordinate System

4. Exponential Co-ordinate System

)Sin(wtIi m

1. In Rectangular Co-ordinate system ;= X + j Y

Where X = ImCos and

Y = ImSin

2. In Polar Co-ordinate System ;3. In Trigonometric Co-ordinate System ;i = ImCos + j Im Sin

4. In Exponential Co-ordinate System ;

Ii m jm eIi

Chapter 8

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Prepared By :




Ganpat Vidyanagar,

Kherva - Mehsana

37

Chapter 8Protection and Utilization of Electrical Power

37


Chapter 8

PROTECTION AND UTILIZATION

OF

ELECTRICAL POWER

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Domestic wiring1. One lamp control from one place

There are three types of domestic wiring generally used in domestic application.

2. One lamp control from two places (Staircase wiring)

3. Fluorescent Tube

Sr. No.Position of

Switch

Condition of

Lamp

1 1 ON

2 2 OFF

Switch

Lamp

2

1

AC

One Lamp Control From One Place

I

I

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Switch A

Lamp

2

1

AC

One Lamp Control From Two Place1

2

Switch BPosition of

Switch A

Position of

Switch B

Condition of

Lamp

1 2 OFF

2 2 ON

2 1 OFF1 1 ON

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Disadvantages of HRC Fuse :

1. After each operation, it must be replaced.

2. It cannot be interlocked with other devices.

3. Its contacts can be affected by heat produced during the operation of fuse.

STARTER1. There are also known as High Rupturing Capacity (HRC) fuse.

2. These types of fuses are used for industrial as well as distribution purpose.

3. The HRC type fuses are designed to protect the equipments against very high

current and4. In this type of fuse, the arc produced during the operation of the fuse element is

extinguished by quartz sand powder.

Advantages of HRC Fuse

1. It can interrupt very high current.

2. Its operation is very fast.

3. Inverse time current characteristics.

4. Low cost compared to other protective device.5. Required no maintainace.

6. Their operating characteristics are accurately known.

Advantages :

1. Simplest form of protective device.

2. Automatic operation

3. Very low cost.

4. Required no maintainace.5. Minimum value of current can be interrupted by fuse.

6. Inverse time current characteristics.

Disadvantages :

1. After fuse operation, fuse or fuse element required to be replaced.

2. Replacement process is time consuming.

3. Required characteristics cannot be obtainable.

The current capacity of the fuse wire should not exceed 5 A when used for lighting

load and not exceed 10 A when used for power load.

All the power devices should have different circuit.Total load in the circuit should not exceed 1000 watt and the number of points in

each circuit should not exceeds 10.

The general rules for any domestic wiring are described below;

1. Fuse

2. Miniature Circuit Breaker (MCB)

3. Earth Leakage Circuit Breaker (ELCB)

The three phase system should be indicated by Red (R phase), Yellow (Y phase), Blue

(B phase) and Black (neutral). th

Main Function : Their main function of the protective devices is to detect the faulty

condition and disconnect the faulty parts or circuit from the system.

Construction of FuseGenerally, the three protective devices are used in the household applications as

listed below;1. Fuse Element

Main Function : Function : When current flowing through the fuse element exceeds

its predetermined value then the fuse wire melts down and it interrupts the current

flowing through the circuit. Hence, it protects the circuit from the excessive current.

Capacitor

2. Fuse Body

Types of Fuse

The different types of fuses are given below;

1. Open type fuse

2. Rewirable type or semi-enclosed types fuse

3. Cartridge type fuse4. HRC fuse

Bi-Metallic

Strip

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Fluorescent Lamp or Tube

Fluorescent Lamp

Construction

4. It consist two electrodes P and Q, made in spiral

form, each made from tungsten material.

3. The small amount of mercury and argon gas is filled

in the tube.

1. It is a one type of glass tube.2. This tube is coated by fluorescent powder

(phosphor) internally.

5. These electrodes are coated by electron emitting

material.

Chock

1. The chock is connected in series with the tube light.2. Its main function is to induce the high voltage to

produce the flow of electrons in the tube and to startthe tube light.

3. It also works as ballast.

Starter1. The starter is connected with the tube light.

2. It consist a bimetallic switch which is normally open

and capacitor C.

3. The bi-metallic switch is made from two different

materials having different temperature co-efficient.

4. Its main function is to start the tube light.

5. The capacitor is used to suppress the radio

interference produced due to arc.

General Rules for Wiring

All the switches should be connected on the live wires.Three pin plugs should be used in residential application.All the neutral wires should be linked.All the switch boards should be fixed at height of 1.5 meter from ground level.All the fans should be fixed at height of 2.5 meter from ground level.

Protective Devices

Fuse

3. End Caps

5. Arc Quenching Medium

HRC Fuse


AC

CHOCK

FLOURECENT

LAMPP Q

Fuse Body

End CapEnd Cap

Terminals TerminalsFuse

Element

Vacuum orQuartz Sand

powder

4. Terminals

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Sr. No. MCB ELCB

1Full Name : Miniature Circuit

Breaker.

Full Name : Earth Leakage Circuit

Breaker.

2For overload and short circuit

protection.For earth leakage protection.

3

It operates when the current

flowing through it exceeds itsrated value.

It operates when the current

flowing through the phase toearth.

4 Rating: Ampere. Rating : mA.

The strip is mounted nearer to

heating resistance which

produce the heat when the

current passing from the

resistance.

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Miniature Circuit Breaker (MCB)

Function : When current flowing through the MCB exceeds its rated value then the

bimetallic strip will be bend which disconnect the faulty parts and it interrupts the

current flowing through the circuit. Hence, it protects the circuit from the excessive

current.


Construction of MCB

1. The MCB consist a bi-metallic strip. The bi-metallic strip is made from two

different materials having different temperature co-efficient.

The spring is used in between

the contacts and the bi-

metallic strip.

Earth Leakage Circuit Breaker (ELCB)

The ELCB is a protective device. It protects the circuit when the leakage current

flowing through the earth. It is always connected in series with earth wire. (In

between outer frame of electrical machine and earth).

In other words, it gives the protection against electric shock. The ELCB is widely usedin the household applications to protect against earth leakage.

Function : When the leakage current flowing through the ELCB, it will operates and its

contacts placed in the main line circuit will be open. Hence, it protects against the

earth leakage.

Difference between MCB and ELCB

Electrical Earthing

Function : The different function of the earthing is describe below;

1. To maintain proper function of the electrical system.

2. To provides the protection to the person against electric shock.

3. To protect the large building against lightning.

4. To maintain constant line voltage.

Necessity of Electrical Earthing

Machine is Not Earthed Machine is Earthed

AC

P

N

Electrical

Machine

Person

Earth

I

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AC

P

N

Electrical

Machine

Person

Earth

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I

I

Heating

Resistance

Bi-metallic

Strip

To Load

Spring

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Types ofEarthing


The earthing can be done by connecting the outer frame of all electrical

appliances/machines to the earth through the low resistance conductor.

There are main two methods for earthing;

1. Pipe Earthing

2. Plate Earthing

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Ground

2 mt

2 mt

Coal

Salt

Coal

Salt

Salt

Coal

Salt

Coal

12 mm Diameter

38 mm G.I. Pipe

15 cm 15 cm

19 mm G.I. Pipe12.7 mm

G.I. Pipe

60 cm

Cement

Concrete

Cast Iron CoverGround


Pipe Earthing

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G.I. Plate

60 cm * 60 cm * 6.3mm

Ground

3 mt

15 cm

90 cm

Plate Earthing

12.7 mm GI. Pipe 19 mm G. I. Pipe

Tunnel

30 cm * 30 cm

60 cm

Alternative

Layer of

Coke & Salt


Cast Iron Cover

Ground

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What is Electric Shock ?


Definition : The nervousness of the human body due to sudden passage of electric

current through the body is known as electric shock.

The electric shock depends on the following factors;

1. Magnitude of current flowing through the body.

2. Time for which the current flowing through the body.

3. Frequency of the current flowing through the body.

4. Physical condition of body of the person.

There are three main types of electrical injuries;

1. Electrocution (death due to electrical shock)

2. Electrical shock

3. Burns

Power Factor

1st Definition : The cosine of the phase angle between the supply voltage applied to

the circuit and the current flowing through the circuit is known as the power factor. It

is denoted by Cos .

2nd Definition : It is also defined as the ratio of resistance to the impedance.

Z

RCos

3rd Definition : It is also defined as the ratio of active power to the apparent power.

CosVI

CosVI

PowerApperant

PowerActiveFactorPower

Disadvantages of Low Power Factor

1. Large Cross Sectional Area of Conductor

2. Higher I2R Losses

3. Lower Efficiency

4. Less Voltage at Terminal

5. Poor Voltage Regulation6. Reduction in KW Capacity

Causes for Low Power Factor

1. Induction Motor

2. Agricultural Pump Set

3. Arc Furnace and Induction Furnace

4. Arc Lamps and Electric Discharge Lamps

5. Arc Welding6. Over Rating of Equipments

7. Increase in System Voltage

Advantages of the Power FactorImprovement

1. Small Cross Section Area of Conductor

2. Increased KW Capacity

3. Reduction in I2R Losses

4. Higher Efficiency

5. Better Voltage Regulation

6. Low Running Cost

Methods to Improve Power Factor

1. Using high power factor motors

2. Using phase advancer with induction motor

3. Using capacitor booster

4. Using static capacitor

5. Using Synchronous condenser 45

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Prepared By :

B.N.ASODARIYA (B.E.ELECTRICAL)


R.K DIPLOMA COLLAGE,

RAJKOT,TRAMBA,

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