Basic Electrical Engineering

597 Pages·2015·7.4 MB·English

by  Rao

Basic Electrical Engineering
Basic
Electrical Engineering
Revised Edition
Dr. K Uma Rao
Professor,
Department of Electrical Engineering,
R V College of Engineering,
Bangalore
Dr.A.Jayalakshmi
AssociateProfessor,
DepartmentofElectricalEngineering,
JNTU,Kukatpally,
Hyderabad
SANGUINE

Sanguine Technical Publishers
Accordingly reduce the stroke size also, for a proportionate reduction.
Bangalore.
2014
Price: `425.00
ISBN 978 9383506 23-1

9 789383 506231 >
Basic Electrical Engineering Revised Edition Dr. K Uma Rao & Dr. A
Jayalakshmi T
his book contains information obtained from authentic and highly regarded
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indicated. Reasonable efforts have been made to publish reliable data and
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© 2014 by Sanguine Technical Publishers, Bangalore – 560 016.
Published by
Lal Prasad for Sanguine. Production Editor: R.Subramanian. Printed in India.
To
umesh, arathi & amrutha
PREFACE
This book is primarily intended for a course in Basic Electrical Engineering. A
strong need was felt for such a book, which would address the needs of Indian
Students hailing from different backgrounds across the country.
The book is written in two parts. Part A covers the important topics of circuit
analysis and basic instrumentation. Part B deals with the concepts of Electrical
Machines.
Part A has six chapters. Chapter 1 of Part A , introduces the student to the two
fundamental laws of Electrical Engineering which form the premise for all other
topics, namely Ohm’s law and Kirchhoff’s laws. Chapter 2 deals with the
fundamental concepts in Electromagnetism—definitions of fundamental
quantities, Biot-Savart’s law, Faraday’s laws, Self Inductance and mutual
Inductance. Chapter 3 covers the various methods of circuit analysis—nodal
analysis, mesh analysis, superposition theorem, Thevenin’s theorem, Norton’s
theorem, maximum power transfer theorem, reciprocity theorem, star-delta
transformation—applied to simple dc circuits. Chapter 4 introduces the students
to the fundamentals of ac circuits. Solution of simple series and parallel ac
circuits is presented.
Chapter 5 presents concepts of three phase circuits. Solution of balanced three
phase star and delta connected networks is dealt with in this chapter. The chapter
also discusses the various methods for measurement of three phase power.
Chapter 6 exposes the student to common electrical appliances and electrical
engineering practices we come across in day to day life. The chapter covers the
topics of methods of electrical wiring, choice of cables, simple wiring schemes,
working principle of fuses, principle of MCBs, earthing methods, common
lighting sources, estimation of energy requirement for simple loads, causes and
prevention of electric shocks. Finally, chapter 7 covers basic concepts of
electrical measurement. Moving coil and moving iron instruments ,
dynamometer wattmeter and energy meter are discussed in detail.
Part B is devoted to the treatment of Electrical Machines. Chapter1 presents the
fundamental concepts of electric machines. Chapter 2 deals withdcgenerators.
The construction, principle of operation and derivation of induced emf are
presented in detail. Chapter 3
vii
viii Preface
deals with the operation, types and characteristics of dc motors. It also covers the
important topics of testing and speed control of dc motors. Chapter 4 is devoted
to transformers.
The constructional features, operation, phasor diagram, testing, computation of
efficiency and regulation are discussed in detail. Chapter 5 deals with three
phase induction motors, which are the most rugged and widely used in the
industry. Chapter 6 presents three phase alternators. The construction, emf
equation and different methods of regulation are covered in detail. Chapter 7
covers single phase induction motors. Chapter 8 gives the experimental
procedure for some of the common experiments conducted in electrical
machines laboratory.
All chapters are presented in a simple and lucid manner to facilitate an easy
understanding of the subject. Important concepts are highlighted to emphasize
the need to remember them. Every chapter contains a number of solved
examples to strengthen the learning of the student and help the student, apply the
concepts in various contexts. The examples presented help the students to relate
abstract concepts in Electrical Engineering to practical applications which they
see in their daily lives. Every chapter also gives a number of questions and
unsolved problems for the student to work out. The book can be used as a text
book for a course in Basic Electrical Engineering, a fundamental course in
Electric circuits and also for a basic course in Electrical Machines.
Dr. K. Uma Rao
CONTENTS
Part I Circuits and Measurements 1
1 Basic laws 3
1.1
Introduction
4
1.2
Basic definitions
4
1.2.1
Charge
4
1.2.2
Current
4
1.2.3
Voltage
5
1.2.4
Power
6
1.2.5
Energy
7
1.3
Ohm’s law
7
1.3.1
Resistances connected in series
9
1.3.2
Resistances connected in parallel
9
1.3.3
Division of current in parallel branches 10
1.3.4
Voltage division in series circuit
11
1.3.5
Conductance G (The unit is mhos or Seimens) 12
1.4
Nodes, branches and loops
13
1.5
Kirchhoff’s laws
13
1.5.1
Kirchhoff’s current law (KCL)
14
1.5.2
Kirchhoff’s voltage law (KVL)
14
ix
x Contents
2 Electromagnetism 45
2.1
Introduction
46
2.2
Magnetic force
46
2.2.1
Biot-Savart Law
47
2.2.2
Force on a current carrying conductor
48
2.2.3
Force between two current carrying conductors 50
2.2.4
Magnetic flux
50
2.3
Magnetomotive force and magnetic field strength 52
2.4
Reluctance
55
2.5
Comparison of magnetic and electric circuits 56
2.6
Composite magnetic circuits
56
2.6.1
Composite series circuits
57
2.6.2
Composite parallel circuits
58
2.7
Electromagnetic induction—Faraday’s law 64
2.7.1
Fleming’s right-hand rule
65
2.7.2
Lenz’s law
65
2.7.3
Dynamically induced emf
67
2.7.4
Statically induced emf
67
2.7.5
Self induced emf
67
2.7.6
Inductance
67
2.7.7
Mutually induced emf
68
2.7.8
Mutual inductance
69
2.8
Energy stored in magnetic field
72
2.9
Dot convention
73
2.10 Inductance in series 75
3 Methods of Circuit Analysis 87 3.1
Introduction
88

Contents
xi
3.2
Circuit Elements