Introduction to electrical engineering - GBV to Electrical Engineering ... 7.2 Advantage ofAC 240...
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Introduction to Electrical Engineering Partha Kumar Ganguly Associate Professor Department of Electrical Engineering Shekhawati Engineering College Dundlod, Jhunjhunu Rajasthan PHI Learning PfcO© toiM Delhi-110092 2014
Transcript of Introduction to electrical engineering - GBV to Electrical Engineering ... 7.2 Advantage ofAC 240...
Introduction to
Electrical Engineering
Partha Kumar GangulyAssociate Professor
Department of Electrical EngineeringShekhawati Engineering College
Dundlod, Jhunjhunu
Rajasthan
PHI Learning PfcO© toiMDelhi-110092
2014
wv-
Contents
Preface xix
1. FUNDAMENTALS OF ELECTRICITY
1.1 Introduction 1
1.2 Electric Current 1
1.3 Electrical Power and Electrical Energy1.4 Electrical Circuit Elements 4
1.5 Resistance 4
1.5.1 Connection of Resistance 4
1.6 Division of Current in Parallel Circuits
1.7 Capacitance 15
1.8 Connections of Capacitors 15
1.9 Inductance 16
1.9.1 Connections of Inductors 17
Key Points 19
Exercises 21
Numerical Problems 21
2. CIRCUIT ANALYSIS
2.1 Introduction 24
2.2 Network Elements 24
2.3 Classification of Network 25
2.4 Source of Electrical Energy 26
2.5 Independent Source 26
2.6 Dependent Source 27
2.7 Source Conversion 28
2.8 Kirchhoffs Laws 30
2.9 Cramer's Rule 33
2.10 Nodal Analysis 54
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viii Contents
2.11 Star-Delta and Delta-Star Transformation 60
2.11.1 Delta-Star Transformation 61
2.11.2 Star-Delta Transformation 63
2.12 Superposition Theorem 71
2.13 Thevenin Theorem 82
2.14 Norton's Theorem 95
2.15 Maximum Power Transfer Theorem 104
2.15.1 Maximum Power Transfer Theorem for AC Networks 118
Key Points 125
Exercises 126
Numerical Problems 126
3. WORK, POWER AND ENERGY 148-157
3.1 Effect of Electric Current 148
3.2 Joule's Law 148
3.3 Thermal Efficiency 149
3.4 Quantity of Electricity 151
3.5 Electric Power 151
3.6 Electric Energy 152
3.7 Mechanical Unit of Work, Power and Energy 152
Key Points 156
Exercises 156
Numerical Problems 157
4. ELECTROMAGNETISM 158-175
4.1 Introduction 158
4.2 Magnetic Effect of Electric Current 755
4.3 Direction of Magnetic Lines of Force 158
4.4 Typical Electromagnetic Field 159
4.5 Electromagnet 160
4.6 Current Carrying Conductor Placed in Magnetic Field 161
4.7 Work Law 163
4.8 Biot-Savart Law 164
4.9 Force between Two Parallel Current Carrying Conductors 169
4.10 Magnitude of Mutual Force 170
Key Points 173
Exercises 174
Numerical Problems 175
5. MAGNETIC CIRCUITS
5.1 Introduction 776
5.2 Magnetic Circuit and Its Analysis5.3 Important Terms 777
176-191
776
Contents ix
5.4 Comparison between Magnetic and Electric Circuits 178
5.5 Types of Magnetic Circuits 179
5.5.1 Series Magnetic Circuit 179
5.5.2 Parallel Magnetic Circuit 180
5.6 Magnetization or B-H Curve 182
5.7 Magnetic Hysteresis 182
5.7.1 Hysteresis Loss 184
5.7.2 Importance of Hysteresis Loop 185
Key Points 189
Exercises 189
Numerical Problems 190
6.1 Introduction 192
6.2 Faraday's Laws of Electromagnetic Induction 193
6.3 Direction of Induced Electromotive Force 194
6.4 Dynamically Induced Electromotive Force 196
6.5 Generation of Alternating Voltage and Current 197
6.6 Equation of Alternating Electromotive Force and Current 198
6.7 Important Terms 200
6.8 Statically Induced Electromotive Force 207
6.8.1 Self-induced emf 207
6.8.2 Mutually Induced emf 210
6.9 Coefficient of Coupling 213
6.10 Inductance in Series 214
6.11 Inductance in Parallel 215
6.12 Energy Stored in Magnetic Field 222
6.13 Magnetic Energy Stored in Per Unit Volume 224
6.14 Lifting Power of a Magnet 224
6.15 Closing and Opening of an Inductive Circuit 227
6.16 Rise of Current in an Inductive Circuit 228
6.17 Decay of Current in an Inductive Circuit 229
6.18 Eddy Current Loss 231
Key Points 234
Exercises 236
Numerical Problems 237
6. ELECTROMAGNETIC INDUCTION 192-239
7. SINGLE-PHASE AC CIRCUITS
7.1 Introduction 240
7.2 Advantage of AC 240
7.3 Alternating Voltage and Current 241
7.4 Sinusoidal Alternating Quantity 242
240-333
X Contents
7.5 Values of Alternating Voltage and Current 243
7.5.1 Peak Value 243
7.5.2 Average Value 243
7.5.3 Effective Value or RMS Value 245
7.6 Form Factor and Peak Factor 248
7.7 Phasor Representation of an Alternating Quantity 251
7.7.1 Phasor Diagram Using RMS Value 252
7.7.2 Phasor Diagram of Sine Wave of Same Frequency 252
7.7.3 Phase and Phase Difference 253
7.8 Addition and Subtraction of Alternating Quantities 254
7.8.1 Parallelogram Method 254
7.8.2 Method of Components 255
7.9 AC Circuits 259
7.9.1 AC Through Pure Resistance Only 260
7.9.2 AC Through Pure Inductance Only 262
7.9.3 AC Through Capacitance Only 264
7.10 Skin Effect 266
7.11 Mathematical Representation of Phasors 270
7.11.1 Rectangular Form of Phasor Representation 270
7.11.2 Trignometrical Form of Phasor Representation 270
7.11.3 Polar Form of Phasor Representation 270
7.11.4 Exponential Form of Phasor Representation 271
7.12 Addition and Subtraction of Phasors 272
7.13 Multiplication and Division of Phasors 274
7.14 AC Series Circuit 280
7.14.1 AC Through Resistance and Inductance Series Circuit 280
7.14.2 AC Through Resistance and Capacitance Series Circuit 292
7.14.3 Resistance, Inductance and Capacitance in Series 300
7.15 Series Resonance 302
7.15.1 Q-Factor of Series Resonant Circuit 304
7.16 Parallel AC Circuits 309
7.16.1 Phasor or Vector Method 309
7.16.2 Admittance Method 311
7.16.3 Method of Phasor Algebra or Vector Algebra 313
7.17 Parallel Resonance 316
7.17.1 Q-Factor of a Parallel Resonant Circuit 318
Key Points 326
Exercises 329
Numerical Problems 330
8. THREE-PHASE AC CIRCUITS
8.1 Introduction 334
8.2 Advantages of Three-phase System over Single-phase System8.3 Generation of Three-phase Voltages 335
8.4 Phase Sequence 337
334-374
335
Contents xi
8.5 Interconnection of Three-phases 337
8.5.1 Star or Wye (Y) Connection 338
8.5.2 Mesh or Delta (A) Connection 340
8.6 Power in Three-phase Circuits 343
8.7 Balanced Star-Delta (Y-A) and Delta-Star (A-Y) Conversion 344
8.8 Balance Three-phase Circuit Analysis 345
8.8.1 Method of Converting Three-phase Network to Single-phase Network 345
8.9 Comparison between Star and Delta Systems 345
8.10 Power Measurement in Three-phase Circuits 357
8.10.1 One-wattmeter Method 358
8.10.2 Two-wattmeter Method: Balanced or Unbalanced Load 359
8.10.3 Three-wattmeter Method 365
Key Points 371
Exercises 372
Numerical Problems 373
9. DC MACHINES (GENERATORS AND MOTORS) 375-396
9.1 Introduction 375
9.2 Main Constructional Features 375
9.2.1 Magnetic Field System 376
9.2.2 Armature 377
9.2.3 Commutator and Brush Gear 378
9.3 Equivalent Circuit of a DC Machine Armature 379
9.4 Winding Arrangements 380
9.5 Single-layer and Double-layer Winding 382
9.6 Lap Winding 385
9.7 Wave Winding 388
9.8 emf or Voltage Equation of a DC Machine 391
9.9 Armature Reaction 391
9.10 Commutation 394
9.10.1 Methods of Improving Commutation 394
10. DC GENERATOR 397-444
10.1 Introduction 397
10.2 DC Generator: emf Equation 397
10.3 Types of DC Generator 403
10.3.1 Separately Excited DC Generator 403
10.3.2 Self-excited DC Generator 404
10.4 Characteristics of DC Generators 415
10.5 No Load Characteristic Curve for Self-excited Generator 415
10.6 Voltage Build-up of a Shunt Generator 416
10.7 Critical Field Resistance of a Shunt Generator 417
10.8 Load Characteristics of Shunt Generator 418
xii Contents
10.9 Load Characteristics of Series Generator 418
10.10 Load Characteristic of Compound Generator 420
10.11 Causes of Failure to Build up Voltage in a Generator 420
10.12 Applications of DC Generators 421
10.13 Losses in DC Generator 422
10.14 Other Types of Losses 424
10.15 Power Flow Diagram 424
10.16 Efficiency of a DC Generator 425
10.16.1 Condition for Maximum Efficiency 426
10.17 Parallel Operation of Generators 430
10.17.1 Parallel Operation of DC Series Generator 430
10.17.2 Parallel Operation of DC Shunt Generators 432
10.17.3 Parallel Operation of DC Compound Generators 433
Key Points 440
Exercises 442
Numerical Problems 443
11. DC MOTOR 445-489
11.1 Introduction 445
11.2 Working Principle of DC Motor 445
11.3 Back emf 447
11.4 Determination of Electromagnetic Torque of a DC Motor 448
11.4.1 Shaft Torque 450
11.5 Types of DC Motors 450
11.5.1 Separately Excited DC Motor 451
11.5.2 Self-excited DC Motors 451
11.5.3 Compound Motor 453
11.6 Speed Equation and Speed Regulation 454
11.7 Characteristics of DC Motors 457
11.7.1 Characteristics of DC Shunt Motor 457
11.7.2 Characteristic of DC Series Motor 459
11.7.3 Characteristics of DC Compound Motor 461
11.8 Applications of DC Motors 461
11.9 Speed Control of DC Motors 462
11.9.1 Speed Control of Shunt Motor 462
11.9.2 Speed Control of DC Series Motor 466
11.10 Necessity of a Starter in DC Motor 484
11.10.1 Three Point DC Shunt Motor Starter 485
Key Points 486
Exercises 487
Numerical Problems 488
12. TRANSFORMER 490-553
12.1 Introduction 490
12.2 Working Principle of a Transformer 491
Contents xiii
12.3 Transformer Construction 492
12.4 An Ideal Transformer 494
12.5 Transformer Based on DC 496
12.6 Classification of Transformers 497
12.7 Transformer: emf Equation 497
12.8 Transformer at No-load 503
12.9 Transformer at Load 504
12.9.1 Phasor Diagram of a Loaded Transformer 506
12.10 Mutual and Leakage Fluxes in a Transformer 506
12.11 Actual Transformer 508
12.12 Simplified Equivalent Circuit 509
12.13 Voltage Regulation 511
12.14 Losses in a Transformer 512
12.14.1 Core or Iron Losses 512
12.14.2 Copper Loss 513
12.15 Efficiency of a Transformer 513
12.15.1 Condition for Maximum Efficiency 514
12.16 All-day Efficiency 515
12.17 Auto-transformer 535
12.18 Three-phase Transformer 539
12.18.1 Three-phase Transformer Connections 540
Key Points 546
Exercises 548
Numerical Problems 550
13. AC INDUCTION MOTOR 554-589
13.1 Introduction 554
13.2 Constructional Features of a Three-phase Induction Motor 554
13.3 Production of Rotating Field and Rotation 555
13.4 Principle of Operation of a Three-phase Induction Motor 555
13.5 Slip 556
13.6 Transformer Action 557
13.7 Frequency of Rotor Current 558
13.8 Stator Construction 559
13.9 Rotor Construction 559
13.10 Magnitude of Stator and Rotor emf 561
13.11 Rotor Resistance 562
13.12 Rotor Reactance 562
13.13 Rotor Impedance 563
13.14 Rotor Current and Power Factor 563
13.15 Equivalent Circuit of Rotor 564
13.16 Losses in an Induction Motor 565
13.17 Power States in an Induction Motor 565
13.17.1 Relation between Rotor Copper Losses, Slip and Rotor Input 566
xiv Contents
13.18 Torque Developed by an Induction Motor 566"
13.18.1 Maximum Torque and Its Equation 568
13.18.2 Starting Torque (Ts) 568
13.18.3 Torque-Slip Characteristics 569
13.18.4 Starting Torque of Three-phase Induction Motor 570
13.19 Equivalent Circuit of an Induction Motor 571
13.20 Phasor Diagram of Three-phase Motor 573
13.21 Necessity of a Starter 581
13.22 Starting Methods of Squirrel Cage Induction Motor 582
13.22.1 Direct On Line (DOL) Starter 552
13.22.2 Stator Resistance Starter 583
13.22.3 Auto Transformer Starter 583
13.22.4 Star-Delta Starter 584
13.23 Starting Method of Slip Ring Induction Motor 585
Key Points 586
Exercises 587
Numerical Problems 588
14. ALTERNATOR OR SYNCHRONOUS GENERATOR 590-621
14.1 Introduction 590
14.2 Alternator 590
14.3 Rotating Field 591
14.4 Advantages of Stationary Armature of Alternator 591
14.5 Construction of Alternator 592
14.5.1 Stator 592
14.5.2 Rotor 594
14.5.3 Miscellaneous 595
14.6 Alternator Operation 595
14.7 Speed and Frequency 596
14.7.1 Synchronous Speed 597
14.8 Pitch Factor and Distribution Factor 597
14.9 Excitation Systems for Synchronous Machines 598
14.10 Alternator: emf Equation 599
14.11 Actual Voltage Generated 599
14.12 Alternator at No-load 605
14.13 Alternator at Load 606
14.14 Phasor Diagram of a Loaded Alternator 606
14.15 Armature Leakage Reactance 608
14.16 Armature Reaction in Three-phase Alternator 60814.17 Synchronous Impedance 609
14.17.1 Calculation of Synchronous Impedance (Z,) 609
14.18 Voltage Regulation 610
14.19 Parallel Operation of Alternator 617
Contents XV
Key Points 617
Exercises 618
Numerical Problems 618
15. SYNCHRONOUS MOTORS 622-640
15.1 Introduction 622
15.2 Construction of a Synchronous Motor 622
15.3 Working Principle of a Synchronous Motor 623
15.4 Methods of Starting a Synchronous Motor 624
15.4.1 By Means of an Auxiliary Motor 624
15.4.2 Self-starting by the Use of Damper Winding 625
15.5 Equivalent Circuit and Phasor Diagram of a Synchronous Motor 626
15.6 Power Developed by a Synchronous Motor 628
15.7 Effect of Changing Field Excitation 629
15.8 Synchronous Condenser 630
15.9 Applications of Synchronous Motors 631
15.10 Comparison between Three-phase Synchronous and Induction Motors 632
Key Points 637
Exercises 637
Numerical Problems 638
16.1 Introduction 641
16.2 Disadvantages of Low Power Factor 642
16.3 Causes of Low Power Factor 643
16A Power Factor Improvement 643
16.5 Methods of Power Factor Improvement 644
16.5.1 Power Factor Correction by Synchronous Motor 645
16.5.2 Power Factor Correction by Static Capacitors 645
16.6 Power Factor Correction in Three-phase Systems 646
16.7 Advantages and Limitation of Static Capacitors 648
16.8 Economies of Power Factor Improvement 652
16.8.1 Most Economical Power Factor 652
Key Points 655
Exercises 656
Numerical Problems 656
17. ELECTRICAL MEASURING INSTRUMENTS AND MEASUREMENTS 658-699
17.1 Introduction 658
17.2 Analog and Digital Instruments 658
17.3 Classification of Electrical Instruments 658
17.4 Utilization of Effects in Analog Instruments 659
16. POWER FACTOR IMPROVEMENT 641-657
xvi Contents
17.5 Indicating Instruments 660
17.6 Moving Iron Instrument 663
17.6.1 Attraction Type Moving Iron Instruments 663
17.6.2 Repulsion Type Moving Iron Instruments 665
17.6.3 Advantages and Disadvantages of Moving Iron Instruments 667
17.6.4 Applications of Moving Iron Instruments 667
17.7 Permanent Magnet Type Moving Coil Instruments 668
17.7.1 Advantages and Disadvantages of Permanent Magnet Type
Moving Coil Instruments 677
17.8 Dynamometer Type Instruments 671
17.9 Dynamometer Type Wattmeter 672
17.9.1 Advantages and Disadvantages of Dynamometer Type Wattmeter 676
17.10 Rectifier Instruments 678
17.10.1 Limitations and Applications of Rectifier Instruments 679
17.11 Extension of Range of Ammeters and Voltmeters 680
17.11.1 Extension of Range of Moving Coil Ammeter 680
17.11.2 Extension of Range of Moving Coil Voltmeter 681
17.12 Sensitivity 683
17.13 Extension of Range of AC Instruments 683
17.13.1 Advantages of Instrument Transformers 685
17.14 Induction Type Single-phase Energy Meter 685
17.14.1 Errors in an Induction Type Energy Meter and Their Adjustments 688
17.15 Megger 690
17.16 Wheatstone Bridge 692
17.17 Slide Wire Bridge 693
17.18 DC Potentiometer 694
17.19 AC Bridge 695
Key Points 696
Exercises 697
Numerical Problems 698
18. GENERATION OF ELECTRIC POWER 700-722
18.1 Introduction 700
18.2 Sources of Energy 700
18.3 Salient Features of a Modern Coal-fired Steam Power Plant 700
18.3.1 Choice of Site for a Coal-fired Power Plant 704
18.3.2 Superthermal Power Plants 705
18.4 Hydroelectric Power Plants 705
18.4.1 Main Advantages of Hydroelectric Power Station 705
18.4.2 Limitations of Hydroelectric Plants 706
18.4.3 Choice of Site for Hydroelectric Power Station 706
18.4.4 Classification of Hydroelectric Plant 708
18.4.5 Surge Tanks 711
18.4.6 Hydro Potential in India 711
Contents xvii
18.5 Nuclear Power Plant 711
18.5.1 Main Parts of a Reactor 712
18.5.2 Selection of Site for Nuclear Power Plants 713
18.5.3 Merits of Nuclear Power Plant 714
18.5.4 Limitation of Nuclear Power Plants 714
18.5.5 Classification of Reactor 715
Key Points 721
Exercises 722
19. FRACTIONAL HORSE POWER MOTOR 723-754
19.1 Introduction 723
19.2 Single-phase Induction Motor 724
19.2.1 Torque Produced for Self-starting By Single-phase Induction Motor 725
19.3 Split Phase Induction Motor 726
19A Capacitor Motors 728
19.4.1 Capacitor Start Motor 728
19.4.2 Capacitor Start Capacitor Run Motor 730
19.4.3 Permanent Split Capacitor (PSC) Single-phase Induction Motor 732
19.5 Shaded Pole Motor 733
19.6 AC Series Motor or Commutator Motor 735
19.7 Single-phase Synchronous Motor 738
19.7.1 Reluctance Motor 738
19.7.2 Hysteresis Motor 740
19.8 Servo Motor 741
19.8.1 DC Servo Motor 742
19.8.2 AC Servo Motors 742
19.8.3 Comparison of Servo Motors with Conventional Motors 744
19.9 Universal Motors 744
19.10 Stepper Motors 746
19.10.1 Variable Reluctance Stepper Motor 747
19.10.2 Permanent Magnet Stepper Motor 748
19.10.3 Hybrid Stepper Motor 749
19.10.4 Application of Stepper Motor 749
19.11 Permanent Magnet DC Motor 750
Key Points 751
Exercises 753
BIBLIOGRAPHY 755
INDEX 757-760
