ELECTRICAL ELECTRONICS ENGINEERING

Size: px

Start display at page:

Download "ELECTRICAL ELECTRONICS ENGINEERING"

Cuthbert Ross
5 years ago
Views:

2 ELECTRICAL AND ELECTRONICS ENGINEERING (Strictly as per latest RGPV Syllabus) SANJEEV GUPTA B.E., M.B.A. DHANPAT RAI PUBLICATIONS (P) LTD. 22, ANSARI ROAD, DARYAGANJ, NEW DELHI Ph.: , ishkapur@vsnl.com

3 Price : Rs First Edition : 2011 Author Published by: Ish Kapur for Dhanpat Rai Publications (P) Ltd., Typeset by Phoenix Computer Centre, and Printed at Taj Press, New Delhi. DISCLAIMER: Every effort has been made to avoid errors or omissions in this publication. In spite of this, some errors might have crept in. Any mistake, error or discrepancy noted may be brought to our notice which shall be taken care of in the next edition. It is notified that neither the publisher nor the authors or seller will be responsible for any damage or loss of action to any one, of any kind, in any manner, therefrom. No part of this book may be reproduced or copied in any form or by any means [graphic, electronic or mechanical, including photocopying, recording, taping, or information retrieval system] or reproduced on any disc, tape, perforated media or other information storage device, etc., without the written permission of the author and publishers. Breach of this condition is liable for legal action. For binding mistakes, misprints or for missing pages, etc., the publisher's liability is limited to replacement within one month of purchase by similar edition. All expenses in this connection are to be borne by the purchaser. All disputes are subject to Delhi jurisdiction only.

4 PREFACE TO THE FIRST EDITION The book Electrical and Electronics Engineering has been written for the first year Engineering Students according to the latest RGPV Syllabus. The aim of writing this book is to provide the students with a clear and logical presentation of the subject, basic concepts, principles and their link with physical phenomena. The book is written in a very simple way and every effort has been made to make the treatments simple, comprehensive and complete. The subject matter has been developed in a step by step way for easy understanding. Throughout the book, the stress has been given on fundamental concepts through illustrative examples and figures. To clarify the concepts and making the topics interesting, a number of solved examples are incorporated at appropriate places. Practical exercises, problems and a number of objective type questions with their answers are given at the end of each chapter. The book is divided into five units. The first unit is devoted to the basic ideas of Electrical Circuit Analysis including the different theorems used for Circuit Analysis. The second unit emphasises on the Basic Concepts of Transformers. The constructional details, working principles and explanations of D.C. Machine, Induction Machine and Synchronous Machine are discussed in the third unit under the head of Rotating Electric Machines. Unit fourth explains the different number systems, theorems and different gates under Digital Electronics. The last unit fifth throws light on the Electronic Components and Circuits which are the basis of Electronic Engineering. Inspite of my best efforts, it is possible that some unintentional errors might have crept in. I shall acknowledge with gratitude any such errors brought to my notice. Suggestions from students and Professors for improvement of the book would be thankfully acknowleged. I hope that the book will be useful for the readers. DELHI Sanjeev Gupta

5 SYLLABUS (RGPV Syllabus) ELECTRICAL AND ELECTRONICS ENGINEERING B.E UNIT - I Electrical Circuit Analysis: Voltage and current sources, dependent and independent sources, source conversion, DC circuits analysis using mesh and nodal method, Thevenin s and superposition theorem, star-delta transformation. 1-phase AC circuits under sinusoidal steady state, active, reactive and apparent power, physical meaning of reactive power, power factor, 3-phase balanced and unbalanced supply, star and delta connections. UNIT - II Transformers: Review of laws of electromagnetism, mmf, flux, and their relation, analysis of magnetic circuits. Single-phase transformer, basic concepts and construction features, voltage, current and impedance transformation, equivalent circuits, phasor diagram, voltage regulation, losses and efficiency, OC and SC test. UNIT - III Rotating Electric Machines: Constructional details of DC machine, induction machine and synchronous machine, working principle of 3-Phase induction motor, EMF equation of 3-Phase induction motor, concept of slip in 3-Phase induction motor, explanation of Torque-slip characteristics of 3-Phase induction motor, classification of self excited DC motor and generator. UNIT - IV Digital Electronics: Number systems used in digital electronics, decimal, binary, octal, hexadecimal, their complements, operation and conversion, floating point and signed numbers, Demorgan s theorem, AND, OR, NOT, NOR, NAND, EX-NOR, EX-OR gates and their representation, truth table, half and full adder circuits, R-S flip flop, J-K flip flop. UNIT - V Electronic Components and Circuits: Introduction to Semiconductors, Diodes, V-I characteristics, Bipolar junction transistors (BJT) and their working, introduction to CC, CB and CE transistor configurations, different configurations and modes of operation of BJT, DC biasing of BJT.

6 CONTENTS Preface to the First Edition (iii) UNIT - I ELECTRICAL CIRCUIT ANALYSIS Voltage and Current Sources Independent and Dependent Sources Source Conversion Kirchoff s Laws D.C. Circuit Analysis using Mesh Method 1.7 Solved Examples D.C. Circuit Analysis using Nodal Method 1.17 Solved Examples Theorem Superposition Theorem 1.23 Solved Examples Thevenin s Theorem 1.27 Solved Examples Star-delta Transformation 1.35 Solved Examples Terms Related to Sinusoidal Waveform Active Power and its Value in Pure Resistive Circuit Active and Reactive Power in Inductive Circuit Active and Reactive Powers in Pure Capacitive Circuit Power in General Series circuit Physical Meaning of Reactive Power Physical meaning of Power Factor 1.49 Solved Examples Introduction to Three Phase Systems Three-Phase Balanced and Unbalanced Supply Star and Delta Connections Three-Phase Circuit Voltages/Currents [Double Subscript Notation] Star Connection (Voltage and Current Relations) Delta Connection (Current Relationship) Power Equations in Three-Phase Circuits 1.58 Solved Examples Comparison Between Star and Delta Connections 1.60 Exercises and Problems 1.62

7 (vi) Contents UNIT - II TRANSFORMERS Electromagnetic Induction and Electromagnetism Review of Laws of Electromagnetism Few Definitions Magentic Circuit Comparison Between Magnetic and Electric Circuits Magnetic Circuit with Air Gap 2.7 Solved Examples Introduction to Transformer Basic Principle and Operation Construction of Transformer Ideal Transformer E.M.F. Equation of a Transformer 2.15 Solved Examples Transformer on No-Load (Secondary Operation) Transformer on Load Phasor Diagram of a Loaded Transformer 2.20 Solved Examples Equivalent Values Referred to Primary Equivalent Circuit (Using Voltage, Current and Impedance Transformation) 2.23 Solved Examples Losses in a Transformer 2.28 Solved Examples Efficiency Condition for Maximum Efficiency of a Transformer 2.31 Solved Examples Voltage Regulation 2.33 Solved Examples Condition for Maximum Regulation Open Circuit or no Load Test (O.C. Test) Short Circuit or Impedance Test (S.C. Test) 2.38 Solved Examples 2.38 Exercises and Problems 2.43 UNIT - III ROTATING ELECTRICAL MACHINES Introduction to Electro-Mechanical Energy Conversion Construction of A DC Machine Types of Armature winding Introduction to Synchronous Machine Constructional Features of A Synchronous Machine Synchronous Generator / Alternator Synchronous Motor Introduction to Induction Machine Construction of 3-Phase Induction Motors Working Principle of 3-Phase Induction Motor Concept of Slip 3.12

8 Contents (vii) 3.9 Rotor Current (or EMF) Frequency 3.13 Solved Examples EMF Induced in Rotor Rotor Reactance, Current and Power Factor 3.16 Solved Examples Rotor Torque τ Torque Slip Characteristics 3.18 Solved Examples Classification of Self-Excited D.C. Motors Classification of Self Excited D.C. Generators 3.22 Exercises and Problems 3.23 UNIT - IV DIGITAL ELECTRONICS Introduction The Decimal Number System Binary Number System Decimal to Binary Conversion Binary to Decimal Conversion The Octal Number System Conversion of Octal Number into Decimal Number Conversion of Decimal Number into Octal Number Conversion of Octal Number into Binary Number Conversion of Binary Number into Octal Number Hexadecimal Number System Conversion of Hexadecimal Number into Decimal Number Conversion of Decimal Number into Hexadecimal Number Conversion of Binary Number into Hexadecimal Number Conversion of Hexadecimal into Binary Number Binary Addition Binary Substraction Floating Point Numbers Signed and Unsigned Number 1 s and 2 s Complements s Complemental Subtraction s Complemental Subtraction s and 10 s Complements in Decimal Number System Binary Multiplication and Division Boolean Algebra Laws of Boolean Algebra Basic Logic Gates OR Addition AND Multiplication The NOT Circuit De-Morgan s Theorem NAND Gate NAND Gate is a Universal Gate NOT Gate NOR Gate is a Universal Gate 4.42

9 (viii) Contents 4.35 Exclusive-or Gate (XOR Gate) Exclusive-nor Gate (Ex-NOR Gate) Logic Gates at a Glance Half-Adder Full Adder Half Subtractor Full Subtractor Sequential Logic Circuits Rs Flip-flop 4.51 Exercises and Problems 4.54 UNIT - V ELECTRONIC COMPONENTS AND CIRCUITS Introduction to Semiconductors Chemical Bonds in Semiconductors like Germanium and Silicon Effect of Temperature on Semiconductors Mechanism of Conduction in Electrons and Holes Pure or Intrinsic Semi-conductors and Impure or Extrinsic Semi-conductors N-type Extrinsic Semiconductor P-type Extrinsic Semiconductor Majority and Minority Charge Carriers Mobile Charge Carriers and Immobile Impure P-N Junction Diode Working of Diode Volt-Ampere Characteristics of P-N Junction Important Terms The Bipolar Junction Transistor (BJT) Transistor Biasing Different Modes of Operation of a Transistor Operation of PNP Transistor Operation of NPN Transistor Transistor Circuit Configurations Common-Base (CB) Configuration Common-Emitter (CE) Configuration Common-Collector (CC) Configuration Characteristics of Common Base Circuit Characteristics of Common Emitter Circuit D.C. Equivalent Circuit 5.36 Solved Examples Transistor Biasing Different Methods for Transistor Biasing Base Resistor Method Collector to Base Bias Base Bias with Collector and Emitter Feedbacks Self Bias or Emitter Bias (Voltage Divider Bias) Transistor Biasing 5.40 Solved Examples 5.54 Exercises and Problems 5.62

10 UNIT-1 ELECTRICAL CIRCUIT ANALYSIS INTRODUCTION Electricity is modern society s most convenient, useful and popular form of energy. It has numerous applications such as lighting, heating, cooling, transportation, entertainment and so on. Modern human being is totally dependent on electricity and we cannot even think of a life without it. In short, electricity has now become the universal medium for transmission and utilization of energy. The subject of Electrical Engineering forms a basic course for all Engineering graduates as it provides a foundation for all branches of engineering. In one way or the other electricity and in turn laws of electrical engineering provide a base for all branches of engineering. This chapter is devoted to Electrical Circuit Analysis. The following electric circuit terminology are used: (i) Circuit. It is a conducting path through which an electric current either actually flows or is intended to flow. (ii) Parameters. The various elements such as resistance, inductance, capacitance, etc of an electric circuit are called as parameters. (iii) In terms of circuit parameters, a circuit may be: (a) Linear circuit, (b) Non-linear circuit (c) Bilateral circuit (d) Unilateral circuit (a) Linear circuit. If the circuit parameters do not change with voltage or current, the circuit is called as linear circuit. (b) Non-linear circuit. When the circuit parameters change with voltage or current, the circuit is called as non-linear circuit. (c) Bilateral circuit. When the properties or characteristics of a circuit are same in either direction, it is called bilateral circuit. Transmission lines are the example of bilateral circuit. (d) Unilateral circuit. When the properties or characteristics are not same in either direction, the circuit is called as unilateral circuit. Diode is an example of unilateral circuit. (iv) Electric network. When various electrical elements (resistance, inductance, capacitance etc) are connected in a circuit in any manner (in series or parallel), it is called as electric network. The electric network may be: (a) Passive network (b) Active network (a) Passive network. When a network does not contain any source of e.m.f in it, it is called as passive network. (b) Active network. When a network contains at least one source of e.m.f. in it, it is called as active network.

11 1.2 Electrical and Electronics Engineering (v) Active element. The element which supplies energy to the circuit is called as active element. For example, a battery connected in the circuit is an active element. (vi) Passive element. The element which receives energy in a circuit is called as passive element (such as resistor, inductor and capacitor). (vii) Node. A point in the network where two or more circuit elements are joined is called a node. (viii) Branch. The part of the network that lies between the two junctions is called as branch. 1 1 VOLTAGE AND CURRENT SOURCES Source A Source is a device which converts mechanical, chemical, thermal or some other form of energy into electrical energy. Hence, we can say that source is an active network element meant for generating electrical energy. The different types of sources available are voltage sources and current sources. A voltage source has the forcing function of e.m.f. whereas the current source has the forcing function of current. Example of voltage sources are batteries and alternators. Example of current sources are photo electric cells, collector current of transistors etc. These sources are further categorised as ideal source or practical source. Voltage Source A voltage source is a two terminal device whose voltage at any instant of time is constant and is independent of the current drawn from it. Such a voltage source is called as ideal voltage source and have zero internal resistance. In practice, such an ideal voltage source cannot be obtained. However, smaller is the internal resistance r of a voltage source, closer it is to an ideal source. Fig. 1 1 shows an ideal voltage source and a practical voltage source. Fig. 1 1 Let the ideal voltage of the voltage source is 12 V (No load current). If its internal resistance is 0.01 Ω and the load current increases to 100 A, then voltage of ideal voltage source, V 0 = 12 volt. and voltage of practical voltage source V 0 = 12 1 = 11 volt. Figure 1 2 shows the symbol and characteristics of an ideal voltage source and practical source.

12 Electrical Circuit Analysis 1.3 Fig. 1 2 Current source An ideal current source is a two terminal circuit element which supplies the same current to any load resistance connected across its terminals. It is important to mention here that current supplied by the current source is independent of the voltage of source terminals. Figure 1 3 shows the symbol and characteristics of an ideal and practical current source. Fig INDEPENDENT AND DEPENDENT SOURCES Independent Sources The ideal voltage source and ideal current source discussed in previous article come under the category of independent sources. The independent source is one which does not depend on any other quantity in the circuit. It has a constant value i.e., the strength of voltage or current is not changed by any variation in the connected circuit. Thus, the voltage or current is fixed and is not adjustable. Dependent Sources The source whose output voltage or current is not fixed but depends on the voltage or current in another part of the circuit is called as dependent or controlled source. The dependent source is basically a three terminal device. The three terminals are paired with one common terminal. One pair is referred as input while the other pair as output. For example, in a transistor, the output voltage depends upon the input voltage. The dependent sources are represented by diamond shaped box as shown in Fig The dependent sources can be categorised as: 1. Voltage dependent voltage source Fig. 1 4 (a). 2. Current dependent voltage source Fig. 1 4 (b).

13 1.4 Electrical and Electronics Engineering 3. Voltage dependent current source Fig. 1 4 (c). 4. Current dependent current source Fig. 1 4 (d). Fig. 1 4 Classification of Sources The classification of sources is shown in Fig Fig SOURCE CONVERSION It is most important part of the circuit analysis. To simplify the circuit, certain rules have been framed which are given below: (a) A voltage source having some resistance can be replaced by the current source in parallel with the resistance as shown in Fig Fig. 1 6

14 Electrical Circuit Analysis 1.5 The direction of current source is in the direction of voltage rise. (b) A current source in parallel with some resistance can be replaced by a voltage source in series with the same resistance as shown in Fig Fig. 1 7 (c) Voltage sources in series are transformed, as in Fig Fig. 1 8 (d) Voltage sources in parallel must have same value as in Fig Fig. 1 9 (e) Current sources in parallel are transformed as shown in Fig Fig (f) Current shift property is as shown in Fig

15 1.6 Electrical and Electronics Engineering Fig (i) Voltage shift property is as shown in Fig Fig The above mentioned rules are very helpful in circuit analysis for simplifying the circuit. Example 1. Convert the voltage source of Fig (a) into a current source. Fig Solution. Given V = 20 V and R x = 1 k Ω = Ω Now I = V 20 = R x = = 20 ma The equivalent circuit is shown in Fig (b). 1 4 KIRCHOFF S LAWS Ohm s law is unable to give current in complicated circuits. Kirchoff in 1842, gave two general laws which are extremely useful in electrical circuits. These are : (i) The algebraic sum of the currents at any junction in a circuit is zero, i.e., Σ i = 0 (1)

16 Electrical and Electronics Engineering ebook Publisher : Dhanpat Rai Publications Author : Sanjeev Gupta Type the URL : Get this ebook

R09. 1.a) State and explain Kirchoff s laws. b) In the circuit given below Figure 1 find the current through 5 Ω resistor. [7+8] FIRSTRANKER.

R09. 1.a) State and explain Kirchoff s laws. b) In the circuit given below Figure 1 find the current through 5 Ω resistor. [7+8] FIRSTRANKER. SET - 1 1.a) State and explain Kirchoff s laws. b) In the circuit given below find the current through 5 Ω resistor. [7+8] 2.a) Find the impedance between terminals A and B in the following circuit ().