ELECTRICAL MACHINES. Theory and Practice. M.N. Bandyopadhyay

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1 ELECTRICAL MACHINES Theory and Practice M.N. Bandyopadhyay

2 ELECTRICAL MACHINES Theory and Practice M.N. Bandyopadhyay Director National Institute of Technology Kurukshetra Delhi

3 ELECTRICAL MACHINES: THEORY AND PRACTICE M.N. Bandyopadhyay 2007 by PHI Learning Private Limited, Delhi. All rights reserved. No part of this book may be reproduced in any form, by mimeograph or any other means, without permission in writing from the publisher. ISBN The export rights of this book are vested solely with the publisher. Fourth Printing November, 2014 Published by Asoke K. Ghosh, PHI Learning Private Limited, Rimjhim House, 111, Patparganj Industrial Estate, Delhi and Printed by Rajkamal Electric Press, Plot No. 2, Phase IV, HSIDC, Kundli , Sonepat, Haryana. Copy R 608

4 To Professor Nirmal Kanti Chatterjee and Professor Basudev Barman Ex Vice Chancellor

6 Contents Preface Introduction xiii xv 1. DC Machines Introduction Principle of Operation of DC Machine Components of DC Machine Armature Windings Lap Winding Wave Winding Method of Connection of Windings in the Slot Voltage Equation of a DC Machine Armature Reaction in DC Machines Calculation of Demagnetization and Cross Magnetization Ampereturns Per Pole Compensating Winding Commutation Excitation of DC Machine Build-up of a DC Shunt Generator Critical Resistance and Critical Speed of DC Machine Characteristics of DC Generator Characteristics of Separately Excited DC Generator Characteristics of DC Shunt Generator Determination of Internal and External Characteristics from Open-Circuit Characteristic for DC Shunt Generator Characteristics of DC Series Generator Characteristics of DC Compound Generator 42 v

7 vi Contents 1.9 Parallel Operation of DC Generators Conditions Necessary for Parallel Operation of DC Generators Procedure for Connecting DC Shunt Generators in Parallel Parallel Operation of Compound Generators Principle of Operation of DC Motor Different Types of DC Motors Characteristics of DC Motors Starting of DC Motor Manual Starters Automatic Starters Speed Control of DC Motors Shunt Motor Speed Control Series Motor Speed Control Speed Control with the Power Electronic Devices Braking of DC Motors Plugging Dynamic or Rheostatic Braking Regenerative Braking Application of Various Types of Braking on Different Categories of Motors Testing of DC Machines Swinburne s Test Hopkinson s Test 95 Summary 102 Rreview Questions Transformers Introduction Construction of a Transformer Windings and Their Insulation from the Iron Core Oil of the Transformer Main Tank and Conservator Tank Silicagel Breather Cooling Arrangements Buchholz Relay Bushings Tap-Changing Device Principle of Transformer Operation Equivalent Circuit of Single-Phase Transformer Phasor or Vector Diagram of Single-Phase Transformer Regulation of Transformer 132

8 Contents vii 2.7 Tests on Transformer Polarity Test Open-Circuit Test or No-Load Test Short-Circuit Test Determination of Eddy Current Loss and Hysteresis Loss in Transformers Sumpner s Test or Back-to-Back Test Efficiency Calculation of Transformer All-Day Efficiency of Transformer Autotransformer Three-Phase Transformer Vector Grouping or Phase Group of Three-Phase Transformer Methods of Connections of Three-Phase Transformer Parallel Operation of Single-Phase Transformers Parallel Operation of Transformers with +30 and 30 Phase Shift Load Sharing by Two Transformers in Parallel with Equal Voltage Ratios Load Sharing by Two Transformers in Parallel with Unequal Voltage Ratios Per Unit and Percentage Impedance of Transformer Three Winding Transformers Suppression of Triple Frequency Currents by Tertiary Winding Open-Delta Connection Three-Phase to Two-Phase Conversion by Scott Connected Transformer Three-Phase to One-Phase System Induction Regulator Transformer Diagnostics 177 Summary 185 Review Questions Three-Phase Induction Motor Principle of Rotating Field in Three-Phase Induction Motor Reason for Not Attaining the Rotating Field Speed by the Three-Phase Induction Motor Rotor Slip of Three-Phase Induction Motor Main Difference with the Principle of Transformer Types of Three-Phase Induction Motors Comparison between Squirrel Cage and Wound Rotors 193

9 viii Contents 3.6 Construction of Three-Phase Induction Motor Stator Stator Winding Voltage Equation of Rotating Machine Equivalent Circuit of Three-Phase Induction Motor Vector Diagram or Phasor Diagram of Three-Phase Induction Motor Approximate Equivalent Circuit of Three-Phase Induction Motor Torque Equation of Three-Phase Induction Motor Determination of Maximum Torque of Three-Phase Induction Motor Determination of Approximate Value of the Maximum Torque of Three-Phase Induction Motor Determination of Starting Torque of Three-Phase Induction Motor Approximate Value of Starting Torque Maximum Power Output Torque Slip Characteristics of Three-Phase Induction Motor Tests of Three-Phase Induction Motor Separation of Core Loss from the Windage and Friction Loss No-Load Test Blocked Rotor Test Circle Diagram Starting of Three-Phase Induction Motor Direct-on-Line Starting Reduced Voltage Starting Star-Delta Starting Application of External Resistance to the Rotor Circuit During Starting Deep Bar Squirrel Cage Motor Double Cage Rotor Crawling of Three-Phase Squirrel Cage Induction Motor Cogging of Three-Phase Squirrel Cage Induction Motor Vibration Torques on Three-Phase Induction Motor Impact of Higher Harmonics on Three-Phase Induction Motor Some Generalized Rules for Selecting Rotor Slots Speed Control of Three-Phase Induction Motor Voltage Control Rotor Resistance Control Pole Changing Frequency Control Induction Generator Induction Generator without Capacitor Connection Across It 277

10 Contents ix 3.23 Dynamics of Induction Machine Starting at No-Load Injection of Voltage at Slip Frequency in the Rotor Circuit of Three-Phase Induction Motor Cascade Connection of Three-Phase Induction Motors Braking of Three-Phase Induction Motor Dynamic Braking Regenerative Braking Linear Induction Motor Introduction Mathematical Analysis of Operation of Linear Induction Motor Principle of Operation Characteristic of Linear Induction Motor 298 Summary 299 Review Questions Single-Phase Induction Motor Principle of Operation of Single-Phase InductIon Motor Double-Revolving Field Theory Mathematical Representation of Double-Revolving Field Theory Tests of Single-Phase Induction Motor Starting of Single-Phase Induction Motor Resistance Split-Phase Motor Capacitor Split-Phase Motor Shaded-Pole Motor Optimum Starting Characteristic Resistance Split-Phase Motor Capacitor Split-Phase Motor 332 Summary 339 Review Questions AC Commutator Motor (and Some Special Motors) Introduction Single-Phase AC Series Motor Analysis of the Application of AC Single-Phase Supply to a DC Series Motor Modification Required in the AC Series Motor Design and Construction Compensating Winding and Interpole Winding Arrangements in AC Series Motor Concept of Universal Motor 346

9788120329973 Author : BANDYOPADHYAY, M. N.

11 Electrical Machines: Theory And Practice 25% OFF Publisher : PHI Learning ISBN : Author : BANDYOPADHYAY, M. N. Type the URL : Get this ebook

Contents. Review of Electric Circuitd. Preface ;

Contents. Review of Electric Circuitd. Preface ; Preface ; Chapter 1 Review of Electric Circuitd 1.1 Introduction, 1 1.2 Direct Circuit Current, 1 1.2.1 Voltage, 3 1.2.2 Power, 3 1.2.3 Ohm's Law, 5 1.2.4 KirchhofTs Laws, 5 1.2.4.1 Kirchhoff s Current