Electrical machines / S.K. Sahdev.

S. K. Sahdev, Lovely Professional University, Jalandhar, India
S. K. Sahdev is Associate Dean at the Faculty of Technology and Science at Lovely Professional University, Jalandhar. He has more than thirty-five years of teaching experience. In addition, he has helped industrial units set-up electrical laboratories for testing and developing their products. He has authored six books. His areas of interest include electrical machines, electric drives and power electronics.

Includes bibliographical references and index.

Preface
xxi
Acknowledgements xxiii
1. Electro Magnetic Circuits
1
Introduction 1
1.1
Magnetic Field and its Significance
2
1.2
Magnetic Circuit and its Analysis
3
1.3 Important Terms
3
1.4
Comparison between Magnetic and Electric Circuits
5
1.5 Ampere-turns Calculations
6
1.6
Series Magnetic Circuits
6
1.7
Parallel Magnetic Circuits
7
1.8 Leakage Flux
8
1.9
Magnetisation or B-H Curve
21
1.10 Magnetic Hysteresis
22
1.11 Hysteresis Loss
23
1.12 Importance of Hysteresis Loop
24
Section Practice Problems
24
1.13 Electro Magnetic Induction
28
1.14 Faraday?s Laws of Electromagnetic Induction
29
1.15 Direction of Induced emf
30
1.16 Induced emf
31
1.17 Dynamically Induced emf
31
1.18 Statically Induced emf
33
1.19 Self Inductance
34
1.20 Mutual Inductance
34
1.21 Co-efficient of Coupling
35
1.22 Inductances in Series and Parallel
36
1.23 Energy Stored in a Magnetic Field
41
1.24 AC Excitation in Magnetic Circuits
42
1.25 Eddy Current Loss
44
Section Practice Problems
46
1.26 Electro-mechanical Energy Conversion Devices
48
1.27 Torque Development by the Alignment of Two Fields
49
1.27.1 Soft Iron Piece Placed in the Magnetic Field
49
1.27.2 Permanent Magnet Placed in the Magnetic Field
51
1.27.3 Electromagnet Placed in the Magnetic Field
53
1.28 Production of Torque
54
1.28.1 In Case of Permanent Magnet
55
1.28.2 In Case of Electromagnet
55
1.29 Production of Unidirectional Torque
57
1.29.1 By Rotating the Main Magnets
58
1.29.2 By Changing the Direction of Flow of Current in the Conductors of
Electromagnet
58
1.30 emf Induced in a Rotating Coil Placed in a Magnetic Field
63
1.31 Elementary Concept of Electrical Machines
68
1.31.1 Operation of Machine as a Generator (Conversion of Mechanical
Energy into Electric Energy)
68
1.31.2 Operation of Machine as a Motor
70
Section Practice Problems
74
Review Questions
74
Multiple Choice Questions
76
2. Single-Phase Transformers
79
Introduction 80
2.1 Transformer
80
2.2
Working Principle of a Transformer
82
2.3
Construction of Transformer
82
2.3.1 Core Material
83
2.3.2 Core Construction
83
2.3.3 Transformer Winding
85
2.3.4 Insulation
88
2.3.5 Bushings
89
2.3.6 Transformer Tank
90
2.4
Simple Construction of Single-phase Small Rating (SAY 2 kVA) Transformers
91
2.5
An Ideal Transformer
94
2.6
Transformer on DC
95
2.7 emf Equation
96
Section Practice Problems
10 0
2.8
Transformer on No-load
103
2.9
Effect of Magnetisation on No-load (Exciting) Current
104
2.10 Inrush of Magnetising Current
106
Section Practice Problems
113
2.11 Transformer on Load
114
2.12 Phasor Diagram of a Loaded Transformer
115
2.13 Transformer with Winding Resistance
118
2.14 Mutual and Leakage Fluxes
119
2.15 Equivalent Reactance
119
Section Practice Problems
122
2.16 Actual Transformer
123
2.17 Simplified Equivalent Circuit
125
2.18 Short Circuited Secondary of Transformer
127
2.19 Expression for No-load Secondary Voltage
128
2.20 Voltage Regulation
129
2.21 Approximate Expression for Voltage Regulation
130
2.22 Kapp Regulation Diagram
131
Section Practice Problems
14 0
2.23 Losses in a Transformer
142
2.24 Effects of Voltage and Frequency Variations on Iron Losses
143
2.25 Efficiency of a Transformer
145
2.26 Condition for Maximum Efficiency
146
2.27 Efficiency vs Load
152
2.28 Efficiency vs Power Factor
152
2.29 All-day Efficiency
154
Section Practice Problems
156
2.30 Transformer Tests
158
2.31 Polarity Test
158
2.32 Voltage Ratio Test
159
2.33 Open-circuit or No-load Test
159
2.34 Separation of Hysteresis and Eddy Current Losses
161
2.35 Short Circuit Test
165
2.36 Back-to-back Test
167
Section Practice Problems
179
2.37 Classification of Transformers
181
2.38 Parallel Operation of Transformers
181
2.39 Necessity of Parallel Operation
182
2.40 Conditions for Parallel Operation of One-phase Transformers
182
2.41 Load Sharing between Two Transformers Connected in Parallel
184
Section Practice Problems
194
2.42 Auto-transformer
195
2.43 Auto-transformer vs Potential Divider
199
2.44 Saving of Copper in an Auto-transformer
199
2.45 Advantages of Auto-transformer over Two-winding Transformer
200
2.46 Disadvantages of Auto-transformers
200
2.47 Phasor Diagram of an Auto-transformer
201
2.48 Equivalent Circuit of an Auto-transformer
203
2.49 Simplified Equivalent Circuit of an Auto-transformer
203
2.50 Conversion of a Two-winding Transformer to an Auto-transformer
205
2.51 Comparison of Characteristics of Auto-transformers and Two-winding
Transformers 207
2.52 Applications of Auto-transformers
208
Section Practice Problems
218
Review Questions
220
Multiple Choice Questions
221
3. Three-Phase Transformers
224
Introduction 224
3.1
Merits of Three-phase Transformer over Bank of Three Single-phase
Transformers 225
3.2
Construction of Three-phase Transformers
225
3.3
Determination of Relative Primary and Secondary Windings in Case of
Three-phase Transformer
227
3.4
Polarity of Transformer Windings
227
3.5
Phasor Representation of Alternating Quantities in Three-phase Transformer
Connections 228
3.6
Three-phase Transformer Connections
229
3.7
Selection of Transformer Connections
233
3.7.1 Star-Star (Yy0 or Yy6) Connections
233
3.7.2 Delta-Delta (Dd0 or Dd6) Connections
236
3.7.3 Star-Delta (Yd1 or Yd11) Connections
238
3.7.4 Delta-Star (Dy1 or Dy11) Connections
239
3.7.5 Delta-Zigzag Connections
241
Section Practice Problems
251
3.8
Parallel Operation of Three-phase Transformers
252
3.9
Necessity of Parallel Operation of Three-phase Transformers
253
3.10 Conditions for Parallel Operation of Three-phase Transformers
254
3.11 Load Sharing between Three-phase Transformers Connected in Parallel
25
5
3.12 Three Winding Transformers (Tertiary Winding)
257
3.12.1 Stabilisation Provided by Tertiary Winding in Star-Star Transf
ormer
260
3.13 Tap-changers on Transformers
265
3.14 Types of Tap-changers
266
3.14.1 No-load (or Off-load) Tap-changer
266
3.14.2 On-load Tap-changer
267
Section Practice Problems
268
3.15 Transformation of Three-phase Power with Two Single-phase Transformers
2
70
3.16 Open-Delta or V-V Connections
270
3.17 Comparison of Delta and Open Delta Connections
274
3.18 T-T Connections or Scott Connections
275
3.19 Conversion of Three-phase to Two-phase and vice-versa
277
3.20 Difference between Power and Distribution Transformers
291
3.21 Cooling of Transformers
291
3.22 Methods of Transformer Cooling
292
3.23 Power Transformer and its Auxiliaries
294
3.24 Maintenance Schedule of a Transformer
296
3.25 Trouble Shooting of a Transformer
297
Section Practice Problems
297
Review Questions
299
Multiple Choice Questions
300
4. DC Generator
301
Introduction 301
4.1 DC Generator
302
4.2
Main Constructional Features
303
4.3
Simple Loop Generator and Function of Commutator
307
4.4
Connections of Armature Coils with Commutator Segments and Location
of Brushes
309
4.5 Armature Winding
311
4.6 Types of Armature Winding
314
4.7 Drum Winding
315
4.8 Lap Winding
316
4.9
Numbering of Coils and Commutator Segments in Developed Winding Diagram 318
4.10 Characteristics of a Simplex Lap Winding
323
4.11 Characteristics of a Multiplex Lap Winding
327
4.12 Equalising Connections and their Necessity
327
4.13 Simplex Wave Winding
330
4.14 Dummy Coils
332
4.15 Applications of Lap and Wave Windings
338
Section Practice Problems
338
4.16 emf Equation
340
4.17 Torque Equation
341
4.18 Armature Reaction
349
4.19 Calculations for Armature Ampere-turns
351
4.20 Commutation
355
4.21 Cause of Delay in the Reversal of Current in the Coil going through
Commutation and its Effect
357
4.22 Magnitude of Reactance Voltage
358
4.23 Good Commutation and Poor Commutation
360
4.24 Interpoles and their Necessity
361
4.25 Compensating Winding and its Necessity
362
4.26 Methods of Improving Commutation
365
Section Practice Problems
366
4.27 Types of DC Generators
368
4.28 Separately-excited DC Generators
368
4.29 Self-excited DC Generators
369
4.30 Voltage Regulation of a DC Shunt Generator
371
4.31 Characteristics of DC Generators
376
4.32 No-load Characteristics of DC Generators or Magnetisation Curve of DC
Generator 376
4.33 Voltage Build-up in Shunt Generators
377
4.34 Critical Field Resistance of a DC Shunt Generator
378
4.35 Load Characteristics of Shunt Generator
379
4.36 Load Characteristics of Series Generators
380
4.37 Load Characteristics of Compound Generator
380
4.38 Causes of Failure to Build-up Voltage in a Generator
381
4.39 Applications of DC Generators
381
4.40 Losses in a DC Generator
382
4.41 Constant and Variable Losses
383
4.42 Stray Losses
384
4.43 Power Flow Diagram
384
4.44 Efficiency of a DC Generator
384
4.45 Condition for Maximum Efficiency
385
Section Practice Problems
387
Review Questions
390
Multiple Choice Questions
392
5. DC Motors
395
Introduction 395
5.1 DC Motor
396
5.2
Working Principle of DC Motors
396
5.3 Back emf
397
5.4
Electro-magnetic Torque Developed in DC Motor
398
5.5 Shaft Torque
399
5.6
Comparison of Generator and Motor Action
399
5.7
Types of DC Motors
401
5.8
Characteristics of DC Motors
405
5.9
Characteristics of Shunt Motors
405
5.10 Characteristics of Series Motors
407
5.11 Characteristics of Compound Motors
408
5.12 Applications and Selection of DC Motors
409
5.12.1 Applications of DC Motors
409
5.12.2 Selection of DC Motors
410
5.13 Starting of DC Motors
411
5.14 Necessity of Starter for a DC Motor
411
5.15 Starters for DC Shunt and Compound Wound Motors
412
5.16 Three-point Shunt Motor Starter
412
5.17 Four-point Starter
414
5.18 Calculation of Step Resistances Used in Shunt Motor Starter
416
5.19 Series Motor Starter
422
Section Practice Problems
423
5.20 Speed Control of DC Motors
428
5.21 Speed Control of Shunt Motors
428
5.21.1 Field Control Method
428
5.21.2 Armature Control Method
429
5.22 Speed Control of Separately Excited Motors
431
5.23 Speed Regulation
432
5.24 Speed Control of DC Series Motors
440
5.24.1 Armature Control Method
440
5.24.2 Field Control Method
441
5.24.3 Voltage Control Method
442
5.25 Electric Braking
451
5.26 Types of Electric Braking
453
5.26.1 Plugging
453
5.26.2 Rheostatic Braking
454
5.26.3 Regenerative Braking
455
Section Practice Problems
457
5.27 Losses in a DC Machine
460
5.28 Constant and Variable Losses
461
5.29 Stray Losses
461
5.30 Power Flow Diagram
462
5.31 Efficiency of a DC Machine
462
5.32 Condition for Maximum Efficiency
463
5.33 Test Performed to Determine Efficiency of DC Machines
471
5.34 Brake Test
472
5.35 Swinburne?s Test
474
5.36 Hopkinson?s Test
479
5.37 Testing of DC Series Machines
487
5.38 Inspection/maintenance of DC Machines
491
5.39 Faults in DC Machines
492
5.40 Trouble Shooting in a DC Motor
492
Section Practice Problems
493
Review Questions
495
Multiple Choice Questions
497
6. Synchronous Generators or Alternators
500
Introduction 501
6.1
General Aspects of Synchronous Machines
501
6.2 Basic Principles
502
6.3
Generator and Motor Action
503
6.4
Production of Sinusoidal Alternating emf
503
6.5
Relation between Frequency, Speed and Number of Poles
504
6.6
Advantages of Rotating Field System over Stationary Field System
504
6.7
Constructional Features of Synchronous Machines
505
6.8
Excitation Systems
509
6.8.1 DC Exciters
509
6.8.2 Static-Excitation System
510
6.8.3 Brushless Excitation System
511
Section Practice Problems
512
6.9 Armature Winding
513
6.10 Types of Armature Winding
513
6.11 Important Terms Used in Armature Winding
515
Section Practice Problems
519
6.12 Coil Span Factor
521
6.13 Distribution Factor
522
6.14 Winding Factor
524
6.15 Generation of Three-phase emf
524
6.16 emf Equation
525
6.17 Wave Shape
526
6.18 Harmonics in Voltage Wave Form
526
Section Practice Problems
534
6.19 Production of Revolving Field
535
6.20 Ferrari?s Principle (Vector Representation of Alternating Field)
539
6.21 Production of Two-phase Rotating Magnetic Field
540
6.22 Production of Three-phase Rotating Magnetic Field
541
6.23 Rating of Alternators
542
6.24 Armature Resistance
542
6.25 Armature Leakage Reactance
543
6.26 Armature Reaction
544
6.27 Effect of Armature Reaction on emf of Alternator
546
6.28 Synchronous Reactance and Synchronous Impedance
548
6.29 Equivalent Circuit of an Alternator and Phasor Diagram
548
6.30 Expression for No-load Terminal Voltage
549
6.31 Voltage Regulation
551
6.32 Determination of Voltage Regulation
552
6.33 Synchronous Impedance Method or emf Method
552
6.33.1 Determination of Synchronous Impedance
553
6.33.2 Determination of Synchronous Reactance
555
6.34 Modern Alternators
556
6.35 Short-Circuit Ratio (SCR)
556
Section Practice Problems
565
6.36 Assumptions Made in Synchronous Impedance Method
566
6.37 Ampere-turn (or mmf) Method
567
6.38 Zero Power Factor or Potier Method
579
Section Practice Problems
591
6.39 Power Developed by Cylindrical Synchronous Generators
592
6.39.1 Power Output of an AC Generator (in Complex Form)
593
6.39.2 Real Power Output of an AC Generator
593
6.39.3 Reactive Power Output of an AC Generator
594
6.39.4 Power Input to an AC Generator (in Complex Form)
594
6.39.5 Real Power Input to an AC Generator
594
6.39.6 Reactive Power Input to an AC Generator
595
6.39.7 Condition for Maximum Power Output
595
6.39.8 Condition for Maximum Power Input
596
6.39.9 Power Equations, when Armature Resistance is Neglected
596
6.40 Two-Reactance Concept for Salient Pole Synchronous Machines
597
6.40.1 Determination of X
d
and X
q
by Low Voltage Slip Test
599
6.41 Construction of Phasor Diagram for Two-Reac tion Concept
600
6.42 Power Developed by a Salient Pole Synchronous Generator
603
Section Practice Problems
610
6.43 Transients in Alternators
611
6.43.1 Sub-transient, Transient and Direct Reactance
613
6.44 Losses in a Synchronous Machine and Efficiency
616
6.45 Power Flow Diagram
617
6.46 Necessity of Cooling
617
6.47 Methods of Cooling
618
6.48 Preventive Maintenance
619
Section Practice Problems
619
Review Questions
620
Multiple Choice Questions
622
7. Parallel Operation of Alternators
626
Introduction 626
7.1
Necessity of Parallel Operation of Alternators
626
7.2
Requirements for Parallel Operation of Alternators
627
7.3 Synchronising Alternators
627
7.4
Conditions for Proper Synchronising
627
7.5
Synchronising Single-phase Alternators
629
7.5.1 Dark Lamp Method
629
7.5.2 Bright Lamp Method
631
7.6
Synchronising Three-phase Alternators
631
7.6.1 Three Dark Lamps Method
632
7.6.2 Two Bright and One Dark Lamp Method
633
7.7
Synchronising Three-phase Alternators using Synchroscope
635
7.8
Shifting of Load
636
7.9
Load Sharing between Two Alternators
637
Section Practice Problems
646
7.10 Two Alternators Operating in Parallel
647
7.11 Synchronising Current, Power and Torque
647
7.12 Effect of Change in Input Power of One of the Alternators
649
7.13 Effect of Change in Excitation of One of the Alternators
650
7.14 Effect of Reactance
651
7.15 Effect of Governors? Characteristics on Load Sharing
652
7.16 Hunting
653
Section Practice Problems
660
Review Questions
661
Multiple Choice Questions
663
8. Synchronous Motors
665
Introduction 665
8.1
Working Principle of a Three-Phase Synchronous Motor
666
8.2
Effect of Load on Synchronous Motor
667
8.3
Equivalent Circuit of a Synchronous Motor
669
8.4
Phasor Diagram of a Synchronous Motor (Cylindrical Rotor)
669
8.5
Relation between Supply Voltage V and Excitation Voltage E
671
8.6
Different Torques in a Synchronous Motor
673
8.7
Power Developed in a Synchronous Motor (Cylindrical Rotor)
673
8.8
Phasor Diagrams of a Salient-pole Synchronous Motor
676
8.9
Power Developed in a Salient-pole Synchronous Motor
679
8.10 Power Flow in a Synchronous Motor
679
Section Practice Problems
700
8.11 Effect of Change in Excitation
701
8.12 V-Curves and Inverted V-Curves
703
8.13 Effect of Change in Load on a Synchronous Motor
704
8.14 Methods of Starting of Synchronous Motors
706
8.15 Synchronous Condenser
707
8.16 Characteristics of Synchronous Motor
710
8.17 Hunting
711
8.18 Applications of Synchronous Motors
712
8.19 Comparison between Three-phase Synchronous and Induction Motors
712
8.20 Merits and Demerits of Synchronous Motor
713
Section Practice Problems
713
Review Questions
716
Multiple Choice Questions
717
9. Three-Phase Induction Motors
721
Introduction 721
9.1
Constructional Features of a Three-Phase Induction Motor
722
9.2
Production of Revolving Field
724
9.3
Principle of Operation
725
9.4
Reversal of Direction of Rotation of Three-Phase Induction Motors
726
9.5 Slip
727
9.6
Frequency of Rotor Currents
728
9.7
Speed of Rotor Field or mmf
729
9.8 Rotor emf
730
9.9
Rotor Resistance
730
9.10 Rotor Reactance
730
9.11 Rotor Impedance
731
9.12 Rotor Current and Power Factor
731
9.13 Simplified Equivalent Circuit of Rotor
732
Section Practice Problems
739
9.14 Stator Parameters
740
9.15 Induction Motor on No-load
740
9.16 Induction Motor on Load
741
9.17 Induction Motor vs Transformer
742
9.18 Reasons of Low Power Factor of Induction Motors
743
9.19 Main Losses in an Induction Motor
744
9.20 Power Flow Diagram
744
9.21 Relation between Rotor Copper Loss, Slip and Rotor Input
745
9.22 Rotor Efficiency
745
Section Practice Problems
752
9.23 Torque Developed by an Induction Motor
752
9.24 Condition for Maximum Torque and Equation for Maximum Torque
753
9.25 Starting Torque
754
9.26 Ratio of Starting to Maximum Torque
754
9.27 Ratio of Full Load Torque to Maximum Torque
755
9.28 Effect of Change in Supply Voltage on Torque
755
9.29 Torque-slip Curve
756
9.30 Torque-speed Curve and Operating Region
757
9.31 Effect of Rotor Resistance on Torque-slip Curve
757
Section Practice Problems
764
9.32 Constant and Variable Losses in an Induction Motor
765
9.33 Main Tests Performed on an Induction Motor
766
9.33.1 Stator Resistance Test
766
9.33.2 Voltage-ratio Test
766
9.33.3 No-load Test
767
9.33.4 Blocked Rotor Test
769
9.33.5 Heat Run Test
770
9.34 Equivalent Circuit of an Induction Motor
773
9.35 Simplified Equivalent Circuit of an Induction Motor
775
9.36 Maximum Power Output
776
9.37 Circle Diagram
781
9.38 Circle Diagram for the Approximate Equivalent Circuit of an Induction Motor
7
82
9.39 Construction of a Circle Diagram for an Induction Motor
783
9.40 Results Obtainable from Circle Diagram
785
9.41 Maximum Quantities
785
9.42 Significance of Some Lines in the Circle Diagram
786
Section Practice Problems
793
9.43 Effect of Space Harmonies
795
9.43.1 Cogging in Three-phase Induction Motors
795
9.43.2 Crawling in Three-phase Induction Motors
795
9.44 Performance Curves of Induction Motors
796
9.45 Factors Governing Performance of Induction Motors
798
9.46 High Starting Torque Cage Motors
798
9.46.1 Deep Bar Cage Rotor Motors
799
9.46.2 Double Cage Induction Motor
800
9.47 Motor Enclosures
807
9.48 Standard Types of Squirrel Cage Motor
810
9.48.1 Class A Motors
811
9.48.2 Class B Motors
811
9.48.3 Class C Motors
811
9.48.4 Class D Motors
812
9.48.5 Class E Motors
812
9.48.6 Class F Motors
813
9.49 Advantages and Disadvantages of Induction Motors
813
9.49.1 Squirrel Cage Induction Motors
813
9.49.2 Slip-ring Induction Motors
814
9.50 Applications of Three-phase Induction Motors
814
9.51 Comparison of Squirrel Cage and Phase Wound Induction Motors
815
9.52 Comparison between Induction Motor and Synchronous Motor
815
9.53 Installation of Induction Motors
816
9.54 Preventive Maintenance of Three-phase Induction Motors
818
Section Practice Problems
819
Review Questions
820
Multiple Choice Questions
822
10. Starting Methods and Speed Control of Three-phase Induction Motors
828
Introduction 828
10.1 Necessity of a Starter
829
10.2 Starting Methods of Squirrel Cage Induction Motors
829
10.2.1 Direct on Line (D.O.L.) Starter
829
10.2.2 Stator Resistance (or Reactance) Starter
831
10.2.3 Star-Delta Starter
832
10.2.4 Auto-transformer Starter
834
10.3 Rotor Resistance Starter for Slip Ring Induction Motors
836
Section Practice Problems
844
10.4 Speed Control of Induction Motors
844
10.5 Speed Control by Changing the Slip
845
10.5.1 Speed Control by Changing the Rotor Circuit Resistance
845
10.5.2 Speed Control by Controlling the Supply Voltage
846
10.5.3 Speed Control by Injecting Voltage in the Rotor Circuit
847
10.6 Speed Control by Changing the Supply Frequency
847
10.7 Speed Control by Changing the Poles
847
10.8 Speed Control by Cascade Method
848
10.9 Speed Control by Injecting an emf in the Rotor Circuit
850
10.9.1 Kramer System of Speed Control
851
10.9.2 Scherbius System of Speed Control
851
Section Practice Problems
854
Review Questions
854
Multiple Choice Questions
855
11. Single-Phase Motors
857
Introduction 857
11.1 Classification of Single-phase Motors
857
11.2 Single-phase Induction Motors
858
11.3 Nature of Field Produced in Single Phase Induction Motors
859
11.4 Torque Produced by Single-phase Induction Motor
860
11.5 Equivalent Circuit of Single-phase Induction Motor
861
11.6 Rotating Magnetic Field from Two-phase Supply
866
11.7 Methods to make Single-phase Induction Motor Self-starting
870
11.8 Split Phase Motors
871
11.9 Capacitor Motors
875
Section Practice Problems
878
11.10 Shaded Pole Motor
879
11.11 Reluctance Start Motor
880
11.12 Single-phase Synchronous Motors
881
11.13 Reluctance Motors
882
11.14 Hysteresis Motors
884
11.15 AC Series Motor or Commutator Motor
885
11.16 Universal Motor
886
11.17 Comparison of Single-phase Motors
888
11.18 Trouble Shooting in Motors
889
Section Practice Problems
890
Review Questions
891
Multiple Choice Questions
892
12. Special Purpose Machines
893
Introduction 893
12.1 Feedback Control System
893
12.2 Servomechanism
894
12.3 Servomotors
894
12.4 DC Servomotors
895
12.4.1 Field-controlled DC Servomotors
895
12.4.2 Armature-controlled DC Servomotors
895
12.4.3 Series Split-field DC Servomotors
896
12.4.4 Permanent-magnet Armature-controlled DC Servomotor
896
12.5 AC Servomotors
897
12.6 Schrage motor
898
Section Practice Problems
903
12.7 Brushless Synchronous Generator
903
12.7.1 Brushless DC Generator
905
12.8 Brushless Synchronous Motor
905
12.9 Three-brush (or Third-brush) Generator
906
12.10 Brushless DC Motors
907
12.11 Stepper Motors
908
12.11.1 Permanent-magnet (PM) Stepper Motor
909
12.11.2 Variable-reluctance (VR) Stepper Motor
912
Section Practice Problems
913
12.12 Switched Reluctance Motor (SRM)
914
12.13 Linear Induction Motor (LIM)
915
12.14 Permanent Magnet DC Motors
917
12.15 Induction Generator
920
12.16 Submersible Pumps and Motors
922
12.17 Energy Efficient Motors
926
Section Practice Problems
929
Review Questions
929
Multiple Choice Questions
930
Open Book Questions
933
Index
949

An extensive and easy-to-read guide covering the fundamental concepts of electrical machines, highlighting transformers, motors, generators and magnetic circuits. It provides in-depth discussion on construction, working principles and applications of various electrical machines. The design of transformers, functioning of generators and performance of induction motors are explained through descriptive illustrations, step-by-step solved examples and mathematical derivations. A separate chapter on special purpose machines offers important topics such as servomotors, brushless motors and stepper motors, which is useful from industrial perspective to build a customized machine. Supported by 400 solved examples, 600 figures, and more than 1000 self-assessment exercises, this is an ideal text for one or two-semester undergraduate courses on electrical machines under electrical and electronics engineering.

Provides in-depth coverage of the performance and applications of transformers, generators, and motors
Contains extensive reader friendly features such as solved examples, review questions, and open book questions with hints
Includes section-wise practice problems including short answer type questions, and numerical questions Provided by publisher.