BASIC ELECTRICAL ENGINEERING

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BASIC ELECTRICAL ENGINEERING FOURTH EDITION C. L. Wadhwa Formerly Professor Department of Electrical Engineering Delhi College of Engineering, Delhi Formerly Dean Faculty of Technology University of Delhi, Delhi PUBLISHING FOR ONE WORLD NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS New Delhi • Bangalore • Chennai • Cochin • Guwahati • Hydcrnbad Jalandhar • Kolkata • Lucknow • Mumbai • Ranchi Visi[ us ac www.newagepublishers.com

Copyright© 2007, 2006, 2004 New Age International (P) Ltd., Publishers Published by New Age International (P) Ltd., Publishers All rights reserved. No part ofthis ebook may be reproduced in any form, by photos tat, microfilm, xerography, or any other means, or incorporated into any information retrieval syslem, eleclronic or mechanical, without the written permission of the publisher. All inquiries should be emailed to [email protected] ISBN (13) : 978-81-224-2947-3 PUBLISHING FOR ONE WORLD NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS 4835/24,Ansari Road, Daryaganj, New Delhi - 110002 Visit us at www.newagepublishers.com

To My mother, who taught me how to hold pen in my little fingers. My father, who taught me modesty and tolerance. My wife, a symbol of mutual trust and mutual respect. My daughter and son, who exhibited a high degree of patience. My students, who made me learn the subject. The Almighty, who has created such a beautiful world.

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PREFACE TO THE FOURTH EDITION In the fourth edition of Basic Electrical Engineering, two more chapters have been added. Chapter i on DC circuits explains the International System of Units and gives clear concepts of electrical circuits, current, voltage or potential, resistance, power and energy. Also, Ohm's law and Kirchoffs laws have been explained with a solution of series and parallel circuits using these laws. Chapter ii on electromagnetic induction explains Faraday's laws of electromagnetic induction and Lenz's law. Laws of electromagnetic forces, dynamically and statically induced e.m.f.'s have also been explained. Further, concepts of mutual and self-inductances, and hysteresis losses and eddy current losses have been discussed. Under AC circuits, in chapter 1, the concepts ofleakage flux, fringing flux, magnetostatic potential, m.m.f. and reluctance have been included. With these additions, the utility of this book has been greatly enhanced. Any constructive suggestion for further improvement of this book will be gratefully acknowledged. C.L. Wadhwa vii

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PREFACE TO THE FIRST EDITION Electrical Engineering has been written as a core course for all engineering students viz. Electronics and Communication, Computer Engineering, Civil, Mechanical Engineering etc. With advancement in technologies in almost all spheres of engineering, it is becoming difficult to provide more than one slot for interdisciplinary courses. However, the author feels that no engineering can work without electric energy. The basic input to all engineering is the electric energy. A basic course on Electrical Engineering is almost essential for all engineering students. Keeping this compulsion in mind and also that this course will normally he offered at the first year level of engineering, the author has made modest effort to give in a concise form various features of Electrical Engineering starting from simple ac circuits to Network theorems, measuring instruments, transformers, various de and ac machines including stepper motor. Various physical phenomenon have been explained using simple language avoiding the rigorus of mathematics. Chapter I deals with the steady state analysis of a.c. series and parallel circuits and series and parallel resonance. Chapter II describes various network theorems, star-delta transformation and methods of mesh and nodal analysis for de networks. Balanced and unbalanced, three phase circuits have been analysed and methods of 3- phase power measurements have been discussed in Chapter III. Measuring instruments like, ammeter, voltmeter, wattmeter and energy meter have been described in chapter IV. Transformer is a very important electrical equipment. The construction, principle of operation, parameter calculations, efficiency and regulation of transformer have been discussed in chapter V. Chapter VI deals in types of de machines, their operation and characteristics, efficiency and speed control and application of these machines. Chapter VII deals into the construction, principle of operation and applications of three phase synchronous motors and stepper motor. Three phase induction motors form atmost 60 to 70% of the total load on power system. These motors have been discussed in chapter VIII including types, construction, principle of operation, methods of starting, torque-slip characteristic, application and single phasing operation. Single phase induction motors find wide application in Office and domestic appliances. Construction, principle of operation and application of these motors have been described in chapter IX. Power systems is the most capital intensive and the most complex system ever developed by man. Chapter X gives in brief, various supply and distribution systems and suggests methods for improvement of power factor. ix

x A large number of problems have been solved to help understand the theory. At the end of each chapter unsolved problems with their answers have been suggested for further practice. At the end, a large number of objective type questions have been added to help the reader to test himself. Any constructive suggestion for the improvement of the book will be gratefully acknowledged. Last but not the least, I with to express my gratitude to my wife Usha, daughter Meenu and son Sandeep for their patience and encouragement during the preparation of the book. -C.L. Wadhwa

CONTENTS Preface to the Fourth Edition .............................................................. ....... ............. ..... (vii) Preface to the First Edition ................ ........ ........ ........... ........ .... ..... ......... .............. ........ (ix) DC CIRCUITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 i.1 International System of Units ................................................................................... 1 i.2 Circuit ................................................ ........... ............ ........... ................... .. ......... .......... 3 i.3 Electric Current . . ........... ............... ........ ......... ............. .......... ...... ........... . .... . ... ............ 3 i.4 Electric Potential ... ................................................................................ .. .......... ......... 4 i.5 Resistance ..... ......... .......... ......................... .................... ............... ............................. .. 6 i.5.1 Conductivity and Conductance .......... .......... ......... ...... . .............. . .... . ... ............ 7 i.6 Power .......... ....... ....... ........... ..... .................... .......... ............ ............... ... ....... ...... .......... 8 i. 7 Energy ..... .............................................. ......... ....................... .... ....... ............. .... .......... 8 i.8 Ohm's Law ............. ......................................... .................... ............................ ............ 8 i.9 Kirchhoffs Laws .... ................................................. ............ ........... .................. ......... 11 i.10 Series Circuits ................. ............... ........ ................................................................... 13 i.10.1 Parallel Circuits ........................................ .. ................. ................ .................. 15 i.10.2 Series Parallel Circuits ................................................................................. 18 ii ELECTROMAGNETIC INDUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 ii.1 Introduction ... ................... ..................................................... ................................... 29 ii.2 Faraday's Laws of Electromagnetic Induction .......... ......... .................................... 29 ii.3 Lenz's Lavv ................ ............................ .............. ........ .......... ....... .................... .......... 30 ii.4 Laws of Electromagnetic Forces .............................................................................. 30 ii.4.1 Fleming's Left Hand Rule ............................................................................. 32 ii.4.2 Flemings Right Hand Rule ......................... .................................................. 33 ii.5 Dynamically Induced EMF (Generator or Motional EMF) ................. .................. 33 ii.5.1 Statically Induced EMF or Transformer EMF ............................................ 34 ii.6 Self Inductance ............................................ ............................................................. 35 ii. 7 Mutual Inductance ....... ............. .... .... ............ ............ .............. ................................. 36 ii.8 Hysteresis Loss ............... ............................. ........................ ............ ............ ............. 38 ii. 9 Eddy Current Loss ................. ................................ ............ ........... ........................... 40 1 A.C. Cl RCU ITS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 1.1 Introduction .. .................... ........................... ........................ ............ ......................... 49 1.2 Phase ................................................... ................................................... .. ........... ...... 51 1.3 The Average Value of a Waveform .... ................................... ................. .................. 52 1.4 The Effective or RMS Value of a Wave ................................... ................. ..... .......... 54 xi

xii 1.4.1 Form Factor . . ........... .............................................. ........................................ 55 1.4.2 Peak Factor or Crest Factor .............. ..... ... ........... ......... .......... ...... ............... 56 1.5 Phasor Diagram . . . . ........ . . . ...... . . . ...... . . . . . ...... . . . ........ . ........ . . . ...... . . . ........ . . . . . .... . . . ...... . . . . . 56 1.5.1 Phasor Algebra ...... ...... ...... ........ ................. .......... ........ ... ........ .............. ........ 57 1.6 Resistance Connected Across a Sinusoidal Voltage ..................... .................. ... ..... 57 1.6.1 Inductor Across Sinusoidal Source . . ........ . . . ...... . . . ........ . . . ...... . . . . . ...... . . . ...... . . . 58 1.6.2 Capacitor Connected Across Sinusoidal Source .......................................... 59 1.6.3 Series R-L Circuit Connected to Sinusoidal Source ......... ...... ....... ............. 60 1.6.4 RC Series Circuit Connected to Sinusoidal Source ........... ...... ................... 61 1.6.5 R-L-C Series Circuit Connected to Sinusoidal Source .... .......... .......... ........ 64 1.7 Parallel R-L Circuit Across Sinusoidal Supply ............... .............. ......................... 66 1.7.1 Parallel R-C Circuit Across Sinusoidal Source . . . ........ . ........ . . . . . .... . . . . . ...... . . . 67 1.7.2 Series Parallel Circuits of R, L and C ..... ............................. ..... ................... 68 1.8 Resonance ................ ...... . . .................... .... . . .... .... ....... ....... .............. ............................ 69 1. 9 Series Resonance . . ........ . . . ...... . . . ...... . . . ........ . . . ........ . ........ . . . ...... . . . ........ . . . .. .. .. . . . ...... . . . . . 70 1.9.1 Quality Factor Q . . . ...... . . . ...... . . . . . ...... . . . .. ...... . ...... .. . . . ...... . . . ........ . . . . . .... . . . . . ...... . . . 74 1.10 Parallel Resonance ...... .... ...... ..... ...... ...... .................... ................. ................ ............. 80 1.10.1 Q of Parallel RLC Circuit ... ............... .............. .............. ................. ............... 85 1.11 Magnetic Circuits . . . . . . . .. . . . ...... . . . .. .. .... . . . ...... . . . ... . .... . . . ..... . . . . .. ...... . ........ . . . . . .... . . . . . ..... .... 91 1.11.1 Analyses between Magnetic and Electric Circuits ...................................... 92 1.11.2 Leakage Flux ... .............. ........................ ...... ...... .... ............. ............. ... ....... ..... 98 1.11.3 Fringing of Flux .... ..... .................. ..... .......... .................... ............ ................... 99 1.12 Dot Convention for Coupled Circuits ........... ........ .............. ...... ...... ..... ............ ...... 102 2 NETWORK THEORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 2.1 Introduction ..... ....... ..... ................ ......... .... ......... .......... .... .................... ............... .... 1 19 2.2 Kirchhoffs Laws .......................... .................... . . ............... ...... ...... .......................... 1 19 2.3 Star-Delta Transformation ......... . .............................. ......... ................................... 122 2.4 Loop Analysis ..... . . . . . ...... . . . ...... . . . ........ . . . ...... . . . ........ . . . ...... . . . ...... . . . ........ . . . . . .... . . . . . ...... . 125 2.5 Nodal Analysis ......... .... ... ........ ........................................ ......... ........... ... ................. 130 2.6 Superposition Theorem ...... . . ... . ... . . . ...... . . . . ..... . . . . ......... . . ... . . . . . . ..... . .... . ....... . . . . .... ..... . . 134 2.7 Thevenin's Theorem ............... ..... ......... ......... ........ ....... ............. ....... .............. ........ 136 2.8 Norton's Theorem .... .... ... ...... ...... .... ...... ................. ... ................... ....... ....... ....... ...... 140 2.9 Maximum Power Transfer Theorem ......... . . . . . . . ..... . .... . ..... . .... . ..... . . . . . . . . . .... . .... .. . . . . .. 144 3 THREE PHASE SUPPLY .... ................ .... ............... 160 3.1 Three Phase Circuits .......... ..... ...... ...... .... ...... .... ......... ......... ........... ....... ........... . . .... 160 3.2 Analysis of Star Circuits ........ ............ ...... ............... ....... ............ .............. ...... ........ 164 3.3 Delta Circuits ................. ......... ..... ......... . . ................. ....... ........... ........ .............. ....... 169 3.4 Measurement of Power in 3-Phase Circuits ...... .............. ........ ............ ................. 1 72

xiii 3.4.1 Three Wattmeter Method ...... ................................ ............................... ...... 172 3.4.2 Two Wattmeter lVIethod .................................. ....... .............................. ....... 173 3.4.3 One Wattmeter Method ........ . . . ..... . . . . ........ . ....... . . . . ........ . ........ . . . ........ . . . ...... . 175 3.5 Measurement of Reactive Power ........................................ ........... .................. ...... 176 4 BASIC INSTRUMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 4.1 Introduction . ........ . . . ...... . . . ...... . . . ....... . . . . ...... . . . ........ . . . ........ . ........ . ....... . . . . . . ...... . . . ...... . 181 4.2 Types of Instruments .................. ....... ...................... ......... .... .... ................. .... .... .... 181 4.2.1 Permanent Magnet Moving Coil Type ..... . .......... . ........ . ........ . ... . ...... . .. ...... . 182 4.2.2 Dynamometer Type Moving Coil Instruments . . .... ....... ............................ 183 4.3 Moving Iron Type ............ ........................ ........................................................... .... 185 4.4 Induction Instruments ....... ................ ........ ..... ....... ........ .............................. ...... .... 186 4.4.1 Induction Disc Type or Shaded Pole Type . . ........ . ........ . . . ........ . . . ...... . . . ...... . 186 4.4.2 Induction Cylinder Type Instrument .... ....... ....... ....................................... 188 4.4.3 The Shunt ....................... ......... ... ........ ............ .... .... ....... ...... ..................... .... 188 4.4.4 High Series Resistance (Voltage Indicating Instrument) ... . . . . . ...... . . . ...... . 189 4.5 Wattmeter . . ................ .... .................................. ....................................................... 192 4.6 Methods of Connection in the Circuit ........ . ........ . . . ........ . ........ . ........ . ... . ...... . ........ . 195 4.7 Energy Meters ............................. ...... ..................................................................... 196 4.7.1 Single Phase Induction Type Energy Meter ............................................. 196 4.7.2 Creep ........... ........... ...... ............. ........... ......................................................... 198 4.7.3 Friction Compensation . . ...... . . . ........ . . . ........ . ........ . . . ........ . ........ . . . . . .... . . . ........ . 198 4.7.4 Meter Phase Angle Error .................. ............ .... ... .............................. ......... 199 4.8 Polyphase Induction Watt Hour Meters .......................... ........... .... .... .................. 199 4.9 Phantom or Fictitious Load .. . . . ........ . ........ . . . ........ . ........ . . . ...... . . . ........ . . . . . .... . . . ........ . 200 5 TRANSFORMER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203 5.1 Introduction . ........ . . . ...... . . . ........ . ........ . . . ...... . . . ........ . . . ........ . ........ . ........ . . . . . ...... . . . ...... . 203 5.2 Construction ............................................................................................................ 204 5.3 EMF Equation of a Transformer ............................ ............................................... 205 5.4 No Load Operation ........... ........................................ .... .... ...................................... 206 5.5 Operation of Transformer Under Load Condition ............................. ........... ....... 208 5.6 Equivalent Circuit ............ ............ ................. ............. .... ... ..................................... 210 5.7 No Load or Open Circuit Test .... ....... ........ ..................... .... ................................... 214 5.8 Short-Circuit Test .... ........ ........................................... ....... ..................................... 215 5.9 Voltage Regulation ................................................... ........... ...... ..... ........................ 217 5.10 Losses in a Transformer . ........ . . . ...... . . . ...... . . . ........ . . . ....... . . ........ . . . ........ . . . ...... . . . ...... . 221 5.11 Efficiency of Transformer ....................................... ............................................... 222 5.12 Polarity of a Transformer ......... ................ ............... .......................................... .... 228 5.13 Testing of Transformers . . .............. ...... .............................. .................... ........ ......... 231

xiv 5.13.1 Sumpner's Test ...... ..... ............................ ........... ..................... . ......... ....... 231 5.14 Auto Transformer .................... . ......... .................................................... . ........ ........ 232 5.14.1 Saving in Copper in Auto Transformer ... .............................................. 234 6 D.C. MACHINES . ... . . . . . . . . . ... . . . . . . . ..... . . . . . . . ... . . . . . . . 245 6.1 Introduction .......... ......... ... .................................... ......... .. ................... .................... 245 6.2 Construction ..... ..... ...... ... ... . . ....... . .. .. . ..... ......... ....... . . . ............ ..... . ....... ... . .. .. .. .. .... ...... 245 6.3 EMF Equations .... . ....... ..... .................. ........ ... ....... . .......... ........ ....................... ....... . 247 6.3.1 Armature Reaction ......... . .... . ..... . . . ...... . . . . . ........ . . ... ...... . . . . ... ...... . . . . . ........ . . . . . .. 248 6.3.2 Commutation ......................... . ......................................... .................. . ......... 251 6.4 Classification of DC Machines ......... . ......................................... .................. . ......... 253 6.5 Magnetisation Characteristics .......... . ................ ........... ....................... . .......... ...... 256 6.6 Terminal Characteristic of Shunt Generator ....... . .. . ........ . . . .... ...... . . .... . .... ....... .... . 257 6.6.1 Series Generator Characteristic ...... . ........... ....... ..................... . . . .......... ...... 257 6.6.2 Load Characteristics of Compound Generator ....................... . . . ........ . ....... 258 6.7 DC Motors ... . .. ....... ....... . ..... ........ ...... . . ........... ....... . . ........ ..... ...... ........ ...... ...... . . ........ 261 6.7.1 DC Shunt Motor .... .................. ...................................... . ...... ...... . ............ .... 261 6.7.2 DC Series Motor . . . .... . ..... . ........ . . . . . ........ . . ... ........ . . ... ........ . . . . . . . ..... ... . ..... . .... . .. 263 6.7.3 DC Motor Starter ......... ........ ........ .................................. . ............ . ............ .... 264 6.8 Losses in DC Machines . ........... ..................... ....... . ........... ............ ............ ............. . 265 6.9 Efficiency of DC Machines ..... ..... .......................... .................... .......... . . . ......... ....... 266 6.10 Swinburne Test . . ... ....... . ..... ........ ... ........ ....... ..... ..... ........... .... ... ...... .... . . ........... . ....... 268 7 THREE-PHASE SYNCHRONOUS MACHINES . . . . . . . . . . . . . . . . . . . . . . . 276 7.1 Introduction . ........... ........ ............................. . ........ . .......... .............. ......................... 276 7.2 Construction . .......... ........ ... .................................... . ................................................. 276 7.2.1 EMF Equation ...................... ........... . .......... . .......... ....... .. ............. . ................ 277 7.2.2 Rotating Magnetic Field . . .......... ........................ . . . . . .. . . . ..... . .. .. . ..... ....... ........ 280 7.2.3 Armature Reaction ...... .......... . .......... . ........ . .......... . ..................... . ................ 283 7.2.4 Open Circuit and Short Circuit Tests on Alternator ........ ........................ 284 7.2.5 Voltage Regulation ........ ............. ......... ....... ......... ....................... . ........ ........ 286 7.2.6 Losses and Efficiency ..... ............................ ... ............ .......... ..... . . . ............ .... 287 7.2. 7 Magnetic Poles in Machines ............ ....... ............... ....... .......... ... . ....... ........ . 288 7.2.8 Steady State Operation ...... ...... ...... ...... .............................. ........ . ................ 288 7.2.9 Power and Torque .............................. ......... .............................. . . . ........ . ....... 289 7.3 Effect of Excitation on Armature Current ......... . ............ .... ................ . ....... ......... 291 7.4 Change of Load . . .... ..... .. . ... .......... ..... ......... ...... .. . ...... ...... ..... .......... ...... . . .. . .... ...... .. . . . 292 7.5 Starting of Synchronous Motor ....... .. ................................................... . ......... ....... 292 7.5.1 Damper Winding Starting ........ .................. .................. ...... ....... . ................ 292 7.5.2 Auxiliary Motor Starting .................. ......................................... . ................ 293 7 .6 Speed Torque Characteristic ........... . ............ ...... ..................... . ........ .... . ........ ........ 294

xv 7. 7 Synchronous Condenser .............. ................. ......... ............ .............. ...... ....... . ......... 294 7.8 Applications ..... ....... ..... ................ ......... .... ......... .......... .... .................... ............... .... 296 7.9 Stepper Motor .... . .......... . .......... . .......... . ................. . . . ................. . ............ . .... . ... . ...... . 299 7.9.1 Permanent Magnet Type ..... .... .......... ........... .... ... .... ...... ...... .... .................. . 299 7.9.2 Comparison of Stepper Motors ........... .......... ...... ... ........... .............. ...... ..... . 302 7.9.3 Application . . . ............... . ... . ............... . . . ........ . . . ........ . .......... . ...... . ... . ...... . ........ . 302 8 THREE-PHASE INDUCTION MOTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304 8.1 Introduction . .......... . ....... ... ................ . . . ...... . . . ........ . . . ...... ...... .............. . ... . ...... . . . ...... . 304 8.2 Construction ..... ....... ..... ....................... ......................... ...... .................. ...... ......... .... 304 8.3 Principles of Operation ........ ............. ..... ...... ...... .......... ..... ..... ............... ....... . ......... 305 8.4 El\/[F and Current Relations ............... ...... .... ........... ........... ................ ......... . ........ . 306 8.5 Mechanical Power Developed . . ........ . . . ................... . ...... . . . ........ . ............ . .... . ... . ...... . 308 8.6 Starting of 3-Phase Induction l\/Iotors ... ................. ....... .............. .... ... ...... ............. 315 8.7 Industrial Application .... ............................. .......... ................... ......... . ... ....... .......... 325 9 SINGLE PHASE INDUCTION MOTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328 9.1 Introduction ..... ....... ..... ....................... ......................... ...... .................. ...... ......... .... 328 9.2 Principle of Operation .. . .......... . .......... . ................. . .......... . ..................... . .... . . . ......... 329 9.3 Starting of Single Phase Induction Motors ......... ... .................... ................. ... ..... . 331 9.4 Application . . . ......... ........ .... ........... ......... .......... ........ ........ .............. ........ ......... ......... 335 9.5 Universal Motor ...... ....... .......... .... ........ .... .... ............. ............. ... ....... ...... ....... . ......... 335 9.6 Synchros .......... .......... ...... ........... ........ ...... .......... . ... ...... ........ ....... .... ..... ................... 337 9.7 DC Tachometer ......................... ....... .............. ........ ......... ................... . .................... 338 9.8 AC Tachometer ......... ... ....... .................. ...... ..... . . .... .... ..... ................... . .................... 338 9.9 Two Phase Servomotor . . .............. ......... . . . .. . . . ........ . .......... .............. ............... . ......... 339 10 POWER SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342 10.1 Introduction . .......... . ............... . ......... . . ........ . . . ........ . . . ................... . ...... . ... . ...... . ......... 342 10.2 Types of Distribution System .......... . ............ ... ............. .......... ..... ..... ......... ...... ..... . 343 10.2.1 The Radial Systems .............. . . . ...... . . . ........ . . . ...... ...... .............. . ... . ...... . . . ...... . 343 10.2.2 The Ring Mains Systems ......... .... ....... ...... ... . . ................................... ......... 344 10.3 Cost Comparison of Supply Systems ................... .................... ....... ............... ...... . 344 10.4 Power Factor Improvement .. . . . ........ . . . ....... ......... .......... . .......... . ........ . . . . . .... ...... ...... 347 10.4.1 Causes of Low p.f . . .... ............... .................. ....... ............. ........ . .............. ...... 349 10.4.2 Methods to Improve p.f . ........................ ......................... ................... ......... 349 10.5 Generation-Non-Conventional Sources ........... ........... ........... ......... ....... ... . ......... 352 10.5.1 Tidal Power .... . . . ........ . ...... . ... . ................ . . ........ . . . ........ . .... ........ . .... . ... . ....... 353 10.5.2 Wind Power .............. ....... ......... .................. ........... ...... ...... ...... ................ . 353 10.5.3 Geothermal Power ....... .............. . . . ....... .......... . . . ......... ............ . .... . . . ......... 354 10.5.4 Wave Power ......... ..... .................... .......... ... ......... ............. .......... ...... ....... . 355

10.5.5 10.5.6 xvi Magneto Hydro Dynamic (MHD) Generation ..... ... . . . . .. .. .. .... ..... . ..... . ..... 356 Solar Energy ....... ........ ...... ... .......... ...... .............. ........ ......... ........ ............. 356 10.6 Conventional Sources . . . . . . . . . . . . . . . ... ...... ... . . . . . . ........ . . . ..... . . . . ... . . . . ... . . . . ..... . ..... . . ... . . ....... . 357 10.6.1 Hydro Station ..... .... ..... ..... ...... ...... . . ..... . ...... . . .......... ...... .... .... . .......... ........ 357 10.6.2 10.6.3 10.6.4 Steam Power Plant . .. . . .... .... .... .. .. ... ........ ..... . . .... ... .. .. ..... ... ........... .... ..... .... 358 Nuclear Power Plant . ..... . . ... . . .... . . . . . . . . . . . . . ....... . . ... . . . . . . . . ... . . . . . . .. ...... .... . . . . ... . 358 The Gas Turbine Plant ................. . . .. .. ...... . ... ... ... ........... . . . ...... . ... . . ..... ..... 358 11 DOMESTIC WIRING .......................................... 361 11.1 Introduction . . ........ ........ ..... ..... .......... . . ... .. .. . . . ...... ....... . . . . ... ........ ... ........... .. .. . ... . . ...... 361 1 1.2 Types of Domestic Wiring ............ . . .... ....... ....... ......... .. . ...... .... . . ........ .......... . ........ ... 361 1 1.2.1 Cleat Wiring . . .... ..... ..... .... . ...... ......... . . .... ... . . .. .. .... ...... ........ ... .... ...... ..... ..... 361 1 1.2.2 11.2.3 1 1.2.4 Wooden/PVC Casing and Capping Wiring ... . ... . .... . . . . . . . . . . . . . . ... . . .. . . ... . . . . .. 362 Toughened Rubber Sheath (TRS or CTS) or Batton Wiring . .. .. . . . . . .... . 363 Conduit Wiring ........ ..... . .... ..... ..... ............. ..................... ........ . . . .. . . . .......... 363 11.3 Specifications of Wires .. . . ... ..... . . . . ... . . . ... . . . . ... ... ...... . . . ...... . ... . . . ... ... . . ..... . . . . . . ... . . . ... . . . . . . 364 1 1.3.1 Size of Conductor ........................... ................... ..... ...... ............ ............... 365 11.4 Distribution Board ...... ......................... ..... . . . ........ . . . ...... ...... ................. ........ .... ..... . 367 11.5 Types of Cables ... ......... .... ..... ... ... .... ....... ... ...... ...... ....... .. . ..... ......... .... ...... . .... ...... . . ... 368 11.6 Lighting Control Circuits . . ......... ..... ...... ............... ..... . . ... ...... .. . .... ........ . . ..... ............ 368 11. 7 Earthing System ... ............... ...... ..... . . ..... ...... ..... .. .. . ... ...... . ... ...... ... ....... ....... ........ .. ... 370 11.8 Fuses and HRC Fuses . ..... . . . . . . . . ..... ... ......... . . . . . . . . . . . . ...... . . . ... . .... . . . . . . . . . . .. . . ..... ... . . . . ..... . 372 1 1.8.1 Calculation of Fuse Rating ........... ....... ..... ..................... ......................... 377 MULTIPLE CHOICE QUESTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 REFERENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401 INDEX ........................................................ 403

CHAPTER • I DC Circuits i.1 INTERNATIONAL SYSTEM OF U N ITS The international system of units abbreviated as SI has been universally accepted for international use in all fields of engineering and day to day requirements. Therefore, all business and even household transactions are conducted in SI units. SI system offers the following advantages over other system of units. 1. There is one and only one unit for each physical quantity. Therefore, a table of conversions from one unit to another is not required. 2. The system is coherent with the derived units. The conversion factor from the original unit to the derived unit is simply a multiplication or division by 1. 3. There are no conversions between electrical and mechanical systems e.g. a motor or an automobile engine is now rated as in kW rather than horse power. Energy is now expressed in watt-sec rather than in Joule etc. There are a large number of quantities (more than thirty) which an electrical engineer deals in. However it is not necessary to assign a standard unit to each quantity as these quantities are functionally related through experiments, mathematical derivation or definitions. The minimum number of quantities required to express the units of all other quantities are known as fundamental quantities. The following are the considerations for selection of fundamental quantities. (i) A minimum number of constant should be required to establish relationship between the various quantities involved in the study of the given discipline. (ii) The measuring units shall he of a practical size. There are seven fundamental units which are listed below with their name, quantity symbol and unit symbol. 1. Length-metre, l, m It is defined in terms of wavelengths of a particular radiation from krypton 86. 2. Mass-kilogram, m kg It is defined equal to the mass of the international prototype kept in Sevres, France. 3. Time-seconds, t, s It is defined in terms of the duration of a specific number of periods of a particular radiation from the cesium-133 atom. 4. Current-ampere, I, A It is defined as the constant electric current in two infinite parallel conductors separated from each other by 1 m, produce a force of 2 x 10-9 Nim.

2 ELECTRICAL ENGINEERING 5. Temperature-Kelvin, T, K 1 It is defined as the fraction 273_16 of the thermodynamic temperature of water at which point it is simultaneously a gas, a liquid and a solid (the trip point). 6. Quantity-mo!, mol It is defined as the amount of substance which contains as many elementary particles as there are atoms in 0.012 kg of carbon 12. 7. Light-Candela, I, Cd It is defined as the light intensity of the freezing point of platinum under specified conditions. The supplementary units used for two and three dimensional problem related to geometry are : 1. Phase angle, radian rad 2. Solid angle, Steradian Sr At serial no. 4 we have taken current as the fundamental quantity. However, from a purely theoretical consideration the fourth fundamental quantity could be taken as charge which has the fundamental unit couloumb. It is possible to derive current from charge and vice versa. However, the reason for selection of current rather than charge as the fundamental quantity is that ampere serves as the link between electrical, magnetic and mechanical quantities and is more readly measured. Even though it is possible to function with the seven fundamental units mentioned above, yet if a set of derived units are defined with special names, the resulting equations and calculations are greatly simplified Table i.1 lists the Derived units in S.I. Table i.1 SI Derived units Expression in Unit Name Quantity Unit Terms of Symbol Symbol Other Units 1. Absorbed dose gray Gy J/kg 2. Activity becquerel Bq s-1 3. Electric farad c F C!V capacitance 4. Electric siemens G s A/V conductance 5. Electric henry L H Wb/A inductance 6. Electric potential volt V,E v W/A difference 7. Electric ohm R Q V/A resistance 8. Energy joule w J N.m 9. Force newton F N kg.m/s2 10. Frequency hertz f Hz s-1

DC CIRCUITS 11. Illuminance lux E 12. Luminous flux lumen