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by Smarajit Ghosh
Electrical Machines, 2nd Edition
Cover Page
Title Page
Copyright
Dedication
Contents
PREFACE
Acknowledgements
Introduction
ELECTROMAGNETISM
DIRECTION OF CURRENT IN A CONDUCTOR
DIRECTION OF MAGNETIC FLUX IN A CONDUCTOR
FLUX DISTRIBUTION OF AN ISOLATED CURRENT-CARRYING CONDUCTOR
FORCE BETWEEN TWO CURRENT-CARRYING CONDUCTORS
FORCE ON A CONDUCTOR IN A MAGNETIC FIELD
GENERATION OF INDUCED EMF AND CURRENT
FARADAY’S LAWS
LENZ’S LAW
INDUCED EMF
MAGNETIC CIRCUITS
MAGNETOMOTIVE FORCE
MAGNETIC FIELD INTENSITY
MAGNETIC FLUX
SINGLE-PHASE CIRCUITS
POWER TRIANGLE
COMPLEX POWER
THREE-PHASE CIRCUITS
ADVANTAGES OF THREE-PHASE SYSTEM
PHASE SEQUENCE
INTERCONNECTION OF THREE PHASES
STAR AND DELTA CONNECTIONS
VOLTAGES, CURRENTS AND POWER IN STAR CONNECTIONS
VOLTAGES, CURRENTS AND POWER IN DELTA CONNECTIONS
MEASUREMENT OF THREE-PHASE POWER
PRINCIPLE OF ENERGY CONVERSION
ENERGY IN THE COUPLING FIELD
ENERGY IN THE FIELD
CO-ENERGY
ELECTRICAL ENERGY INPUT TO THE SYSTEM
ESTIMATION OF MECHANICAL FORCES IN AN ELECTROMAGNETIC SYSTEM
DOUBLY EXCITED SYSTEMS
CYLINDRICAL ROTATING MACHINE
Case 1: Synchronous Motor/Machine
1 Transformers
1.1 DEFINITION
1.2 BASIC PRINCIPLE
1.3 TYPES OF TRANSFORMERS
1.4 CONSTRUCTION OF SINGLE-PHASE TRANSFORMER
1.5 TRANSFORMER WINDINGS
1.6 TERMINALS AND LEADS
1.7 BUSHINGS
1.8 TAPPING
1.9 COOLING OF TRANSFORMER
1.10 TRANSFORMER OIL
1.11 CONSERVATOR AND BREATHER
1.12 BUCHHOLZ RELAY
1.13 TRANSFORMER TANK
1.14 THEORY OF TRANSFORMER
1.15 EMF EQUATION OF A TRANSFORMER
1.16 STEP-UP AND STEP-DOWN TRANSFORMER
1.17 TRANSFORMER ON NO LOAD
1.18 TRANSFORMER ON LOAD
1.19 EQUIVALENT RESISTANCE
1.20 MAGNETIC LEAKAGE
1.21 EQUIVALENT REACTANCE
1.22 TRANSFORMER WITH RESISTANCE AND LEAKAGE REACTANCE
1.23 EQUIVALENT CIRCUIT
1.24 OPEN CIRCUIT TEST OR NO-LOAD TEST
1.25 SHORT CIRCUIT OR IMPEDANCE TEST
1.26 SEPARATION OF CORE (OR IRON) LOSSES IN A TRANSFORMER
1.27 TOTAL APPROXIMATE VOLTAGE DROP OF A TRANSFORMER
1.28 EXACT VOLTAGE DROP
1.29 PER UNIT RESISTANCE, LEAKAGE REACTANCE AND IMPEDANCE VOLTAGE DROP
1.30 VOLTAGE REGULATION OF TRANSFORMER
1.31 CALCULATION FOR VOLTAGE REGULATION
1.32 LOSSES IN A TRANSFORMER
1.33 EFFICIENCY OF A TRANSFORMER
1.34 CONDITION FOR MAXIMUM EFFICIENCY
1.35 ALL-DAY EFFICIENCY
1.36 POLARITY TEST OF A SINGLE-PHASE TRANSFORMER
1.37 SUMPNER’S TEST
1.38 PARALLEL OPERATION OF SINGLE-PHASE TRANSFORMER
1.39 LOAD SHARING BY TWO TRANSFORMERS
1.40 AUTOTRANSFORMERS
1.41 PULSE TRANSFORMER
1.42 WELDING TRANSFORMERS
1.43 CURRENT TRANSFORMER
1.44 POTENTIAL TRANSFORMER
1.45 TAP CHANGING TRANSFORMERS
1.46 OFF-LOAD TAP-CHANGING TRANSFORMERS
1.47 ON-LOAD TAP-CHANGING TRANSFORMERS
1.48 ON-LOAD TAP CHANGER WITH SINGLE PRIMARY WINDING
1.49 PREVENTIVE AUTOTRANSFORMER
1.50 BOOSTER TRANSFORMER
1.51 INRUSH PHENOMENON
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
2 Three-phase Transformers
2.1 ADVANTAGES OF THREE-PHASE TRANSFORMERS
2.2 PRINCIPLE OF OPERATION
2.3 CONSTRUCTION OF THREE-PHASE TRANSFORMERS
2.4 THREE-PHASE TRANSFORMER CONNECTION
2.5 OPEN-DELTA OR V-V CONNECTION
2.6 SCOTT CONNECTION OR T-T CONNECTION
2.7 THREE-PHASE TO TWO-PHASE CONVERSION
2.8 PARALLEL OPERATIONS OF TRANSFORMERS
2.9 THREE-PHASE TO SIX-PHASE CONVERSION
2.10 THREE-WINDING TRANSFORMER
2.11 THREE-PHASE TRANSFORMER CONNECTIONS
2.12 RATING OF TRANSFORMERS
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
3 Basic concepts of Rotating Machines
3.1 ELECTROMAGNETIC TORQUE
3.2 RELUCTANCE TORQUE
3.3 CONSTRUCTIONAL FEATURES OF ROTATING ELECTRICAL MACHINES
3.4 CONSTRUCTION OF DC MACHINES
3.5 RING WINDINGS
3.6 DRUM WINDINGS
3.7 TYPES OF DC WINDINGS
3.8 EQUALIZING CONNECTIONS FOR LAP WINDING
3.9 USES OF LAP AND WAVE WINDINGS
3.10 DUMMY COILS
3.11 PRINCIPLE OF DC GENERATOR
3.12 OPERATION OF A SIMPLE DC GENERATOR WITH A TWO-SEGMENT COMMUTATOR
3.13 PRINCIPLE OF DC MOTOR
3.14 CONSTRUCTION OF SYNCHRONOUS MACHINES
3.15 POLYPHASE INDUCTION MACHINES
3.16 AIR GAP
3.17 PRINCIPLE OF OPERATION OF THREE-PHASE INDUCTION MOTOR
3.18 SYNCHRONOUS SPEED AND SLIP IN INDUCTION MOTOR
3.19 FREQUENCY OF ROTOR CURRENTS
3.20 SPEED OF THE ROTOR MMF
3.21 ELECTRICAL AND MECHANICAL DEGREES
3.22 PITCH FACTOR
3.23 DISTRIBUTION FACTOR
3.24 WINDING FACTOR
3.25 FLUX PER POLE
3.26 GENERATED EMF IN FULL-PITCHED COIL
3.27 EMF GENERATED IN AC MACHINES
3.28 EMF GENERATED IN DC GENERATOR
3.29 CONCEPT OF ROTATING MAGNETIC FIELD
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
4 DC Generators
4.1 TYPES OF DC MACHINES
4.2 DC GENERATOR
4.3 BRUSH DROP
4.4 EMF EQUATION
4.5 DERIVATION FOR E g
4.6 LOSSES IN DC GENERATOR
4.7 STRAY LOSSES
4.8 CONSTANT OR STANDING LOSSES
4.9 POWER STAGES
4.10 EFFICIENCY
4.11 CONDITION FOR MAXIMUM EFFICIENCY
4.12 ARMATURE REACTION IN DC MACHINES
4.13 DEMAGNETIZING AND CROSS-MAGNETIZING CONDUCTORS
4.14 DEMAGNETIZING AMPERE-TURNS PER POLE
4.15 CROSS-MAGNETIZING AMPERE-TURNS PER POLE
4.16 COMPENSATING WINDINGS
4.17 NUMBER OF COMPENSATING WINDINGS
4.18 COMMUTATION
4.19 VALUE OF REACTANCE VOLTAGE
4.20 METHODS OF IMPROVING COMMUTATION
4.21 EQUALIZER RINGS
4.22 CHARACTERISTICS OF DC GENERATORS
4.23 SEPARATELY EXCITED GENERATORS
4.24 NO-LOAD CURVE FOR SELF-EXCITED GENERATORS
4.25 ADVANTAGES AND DISADVANTAGES OF SEPARATELY EXCITED GENERATORS
4.26 VOLTAGE BUILD-UP OF SHUNT GENERATOR
4.27 CONDITIONS FOR BUILD-UP OF SHUNT GENERATOR
4.28 REASONS FOR FAILURE TO BUILD-UP OF SHUNT GENERATORS
4.29 EXTERNAL CHARACTERISTIC OF SHUNT GENERATOR
4.30 VOLTAGE REGULATION
4.31 INTERNAL OR TOTAL CHARACTERISTIC
4.32 EXTERNAL CHARACTERISTIC AND INTERNAL CHARACTERISTIC FROM OCC
4.33 EFFECT OF BRUSH SHIFT ON THE TERMINAL VOLTAGE
4.34 SERIES GENERATOR
4.35 COMPOUND GENERATOR
4.36 PARALLEL OPERATIONS OF DC GENERATORS
4.37 REQUIREMENTS FOR PARALLELING DC GENERATORS
4.38 PARALLEL OPERATION OF SHUNT GENERATORS
4.39 PARALLEL OPERATION OF SERIES GENERATORS
4.40 PARALLEL OPERATION OF COMPOUND GENERATORS
4.41 USES OF DC GENERATORS
4.42 INDICATIONS OF AN OVERLOADED GENERATORS
4.43 CAUSES OF OVERLOADING
4.44 CAUSES OF SPARKING AT BRUSHES OF A DC MACHINE
4.45 CAUSES OF EXCESSIVE HEATING OF GENERATOR ON RUNNING
4.46 CAUSES OF HEATING OF ARMATURE
4.47 CAUSES FOR ABNORMAL SOUND IN DC GENERATOR
4.48 REASONS FOR RAPID BRUSH WEAR IN A DC MACHINE
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE ΩUESTIONS AND ANSWERS
5 DC Motors
5.1 VOLTAGE EQUATION
5.2 BACK EMF
5.3 CONDITION FOR MAXIMUM MECHANICAL POWER
5.4 ARMATURE TORQUE OF A MOTOR
5.5 ROTATIONAL LOSSES OF DC MACHINES
5.6 COMPOUND MOTOR
5.7 RELATION OF SPEED (N) WITH BACK EMF (E b ) AND FLUX ( Φ )
5.8 CHARACTERISTICS OF SHUNT OR SEPARATELY EXCITED DC MOTOR
5.9 CHARACTERISTICS OF DC SERIES MOTOR
5.10 CHARACTERISTICS OF COMPOUND MOTOR
5.11 SPEED REGULATION
5.12 TORQUE AND SPEED OF DC SERIES MOTOR
5.13 SPEED CONTROL OF DC MOTORS
5.13.1 Armature Resistance Control
5.13.2 Field Resistance Control
5.14 WARD-LEONARD CONTROL (VOLTAGE CONTROL)
5.15 NECESSITY OF A STARTER FOR DC MOTORS
5.16 MANUAL STARTER
5.16.1 Three-point Starter
5.17 AUTOMATIC STARTERS
5.17.1 Time Element Starter
5.17.4 Series Current-limit Starter
5.18 STARTERS FOR DC SERIES MOTORS
5.19 DC SHUNT MOTOR STARTER DESIGN
5.20 ELECTRIC BRAKING
5.21 ELECTRIC BRAKING OF SHUNT MOTORS
5.22 ELECTRIC BRAKING OF SERIES MOTOR
5.22.3 Regenerative Braking
5.23 TESTING OF DC MACHINES
5.24 BRAKE TEST
5.25 SWINBURNE’S TEST
5.26 HOPKINSON’S TEST (BACK-TO-BACK TEST)
5.27 SEPARATION OF LOSSES IN A DC MACHINE
5.28 RETARDATION OR RUNNING TEST
5.29 FIELD’S TEST
5.30 USES OF DC MOTORS
5.31 SPECIAL DC MACHINES
5.32 CHARACTERISTICS OF CROSS-FIELD GENERATORS
5.33 BRUSHLESS DC MOTOR
5.34 FEATURES OF BRUSHLESS DC MOTOR
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERES
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
6 Synchronous Generators
6.1 PARAMETERS OF ARMATURE WINDING
6.2 ARMATURE REACTION
6.3 CONCEPT OF SYNCHRONOUS REACTANCE AND IMPEDANCE
6.4 EQUIVALENT CIRCUIT OF AN ALTERNATOR
6.5 VOLTAGE EQUATION OF ALTERNATOR
6.6 PHASOR DIAGRAM OF ALTERNATOR
6.7 VOLTAGE REGULATION
6.8 DETERMINATION OF VOLTAGE REGULATION
6.9 LOAD CHARACTERISTICS OF ALTERNATORS
6.10 OUTPUT POWER EQUATION OF AN ALTERNATOR
6.11 INPUT POWER EQUATION OF ALTERNATOR
6.12 TWO-REACTION THEORY
6.13 TWO-REACTION THEORY OF SALIENT-POLE ALTERNATOR
6.14 TORQUE-ANGLE CHARACTERISTIC OF SALIENT-POLE ALTERNATOR
6.15 MAXIMUM REACTIVE POWER FOR SALIENT-POLE ALTERNATOR
6.16 LOSSES AND EFFICIENCY
6.17 DETERMINATION OF X d AND X q
6.18 CAPABILITY CURVES
6.19 EXCITATION CIRCLE OF AN ALTERNATOR
6.20 PRIME MOVER CHARACTERISTIC
6.21 INFINITE BUS
6.22 NEED FOR PARALLEL OPERATION OF ALTERNATORS
6.23 SYNCHRONIZING PROCEDURES OF ALTERNATOR
6.24 DISTRIBUTION OF LOAD
6.25 SYNCHRONIZING POWER AND SYNCHRONIZING TORQUE COEFFICIENT
6.26 UNITS OF SYNCHRONIZING POWER COEFFICIENT
6.27 SIGNIFICANCE OF SYNCHRONIZING POWER COEFFICIENT
6.28 HUNTING
6.29 OSCILLATIONS OF SYNCHRONOUS MACHINES
6.30 SUDDEN SHORT CIRCUIT OF SYNCHRONOUS GENERATOR
6.31 SHORT-CIRCUIT RATIO
6.32 PROTECTION OF GENERATORS
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
7 Synchronous Motors
7.1 PRINCIPLES OF OPERATION
7.2 ARMATURE REACTION IN SYNCHRONOUS MOTORS
7.3 PHASOR DIAGRAM OF SYNCHRONOUS MOTOR
7.4 OPERATION AT A CONSTANT LOAD WITH VARIABLE EXCITATION
7.5 V CURVES AND INVERTED V CURVES
7.6 COMPLEX POWER INPUT OF SYNCHRONOUS MOTOR
7.7 COMPLEX POWER OUTPUT OF A SYNCHRONOUS MOTOR
7.8 MAXIMUM OUTPUT POWER
7.9 POWER OUTPUT WHEN ARMATURE RESISTANCE IS NEGLIGIBLE
7.10 INPUT REACTIVE POWER WHEN ARMATURE RESISTANCE IS NEGLIGIBLE
7.11 MOTOR CHARACTERISTICS, PERFORMANCE AND CIRCLE DIAGRAM OF A SYNCHRONOUS MOTOR
7.12 TORQUE OF A SYNCHRONOUS MOTOR
7.13 SALIENT-POLE SYNCHRONOUS MOTOR –TWO-REACTION MODEL
7.14 POWER DEVELOPED BY A SALIENT-POLE SYNCHRONOUS MOTOR
7.15 DAMPER WINDINGS
7.16 DAMPING EFFECT
7.17 HUNTING/SURGING OF SYNCHRONOUS MOTORS
7.18 PERIODICITY OF HUNTING
7.19 METHODS OF STARTING OF SYNCHRONOUS MOTORS
7.20 APPLICATIONS OF SYNCHRONOUS MOTOR
7.21 SYNCHRONOUS CONDENSERS
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
8 Polyphase Induction Motors
8.1 ROTOR CURRENT
8.2 ROTOR POWER
8.18 SYNCHRONOUS WATT
8.19 MEASUREMENT OF SLIP
8.20 EQUIVALENT CIRCUIT
8.21 THEVENIN´S EQUIVALENT CIRCUIT OF AN INDUCTION MOTOR
8.22 STARTING OF INDUCTION MOTORS
8.23 STARTING OF SQUIRREL-CAGE MOTORS
8.24 STARTING OF SLIP-RING INDUCTION MOTORS
8.25 NO-LOAD TEST OR OPEN-CIRCUIT TEST
8.26 BLOCKED-ROTOR OR SHORT-CIRCUIT TEST
8.27 DIRECT TESTING OF INDUCTION MOTORS
8.28 CIRCLE DIAGRAM
8.29 SPEED CONTROL OF INDUCTION MOTOR
8.30 COMPARISON BETWEEN WOUND-ROTOR AND CAGE-ROTOR INDUCTION MOTORS
8.31 CRAWLING
8.32 MAGNETIC LOCKING (COGGING)
8.33 DEEP-CAGE ROTORS
8.34 DOUBLE-CAGE ROTORS
8.35 APPLICATIONS
8.36 COMPARISON BETWEEN SYNCHRONOUS AND INDUCTION MOTORS
8.37 FACTORS GOVERNING THE PERFORMANCE OF INDUCTION MOTORS
8.38 EFFECTS OF OPERATING CONDITIONS
8.39 RATINGS OF INDUCTION MOTOR
8.40 COMMON FAULTS IN THREE-PHASE INDUCTION MOTORS
8.41 MOST PROBABALE REASONS FOR WHICH THREE- PHASE INDUCTION MOTORS FAIL TO START
8.42 MOST PROBABALE REASONS FOR WHICH THREE-PHASE INDUCTION MOTORS FAIL TO CARRY LOAD
8.43 SCHRAGE MOTOR
8.44 POWER FACTOR COMPENSATION
8.45 LINEAR INDUCTION MOTOR
8.46 INDUCTION GENERATOR
8.47 ELECTRICAL BRAKING OF POLYPHASE INDUCTION MOTORS
8.48 SYNCHRONOUS-INDUCTION MOTOR
ADDITIONAL SOLVED PROBLEMS
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
9 Single-phase Motors and Special Machines
9.1 CLASSIFICATION OF SINGLE-PHASE INDUCTION MOTORS
9.2 PRODUCTION OF ROTATING FIELD
9.3 WORKING PRINCIPLE OF SINGLE-PHASE INDUCTION MOTOR
9.4 DOUBLE REVOLVING FIELD THEORY
9.5 ROTOR SLIP WITH RESPECT TO TWO ROTATING FIELDS
9.6 EQUIVALENT CIRCUIT OF SINGLE-PHASE, SINGLE-WINDING INDUCTION MOTOR
9.7 POWER DEVELOPED AND LOSSES OF SINGLE-PHASE, SINGLE-WINDING INDUCTION MOTOR
9.8 DETERMINATION OF EQUIVALENT CIRCUIT PARAMETERS
9.9 SPLIT-PHASE INDUCTION MOTORS
9.10 CAPACITOR MOTORS
9.11 PERMANENT SPLIT CAPACITOR MOTORS
9.12 SHADED POLE MOTOR
9.13 SINGLE-PHASE SYNCHRONOUS MOTORS
9.14 SERIES MOTOR OR UNIVERSAL MOTOR
9.15 STEPPER MOTOR
9.16 CHARACTERISTICS OF STEPPER MOTORS
9.17 DC SERVOMOTORS
9.18 AC SERVOMOTORS
9.19 SERVOMECHANISM
SIGNIFICANT POINTS
SHORT QUESTIONS AND ANSWERS
SUPPLEMENTARY PROBLEMS
MULTIPLE-CHOICE QUESTIONS AND ANSWERS
Appendix A: Basic Definition, Hysteresis and Eddy Current Losses
A.1 RESISTANCE AND RESISTIVITY
A.2 INDUCTANCE
A.3 COEFFICIENT OF COUPLING
A.4 DOT CONVENTION
A.5 INDUCTIVE COUPLING IN SERIES
A.6 INDUCTIVE COUPLING IN PARALLEL
A.7 AC OPERATION OF MAGNETIC CIRCUIT
A.8 HYSTERESIS AND EDDY CURRENT LOSSES
Appendix B: Reluctance Motor
Appendix C: MMF of Distributed Winding
Appendix D: Torques in AC and DC Machine
Appendix E: Separation of No-load Losses of an Induction Motor
Appendix F: Separation of Losses of an Induction Motor
Appendix G: Tertiary Windings
Appendix H: Solid State of Drives Control
SPEED CONTROL OF DC AND AC DRIVE MOTORS
SPEED CONTROL OF DC MACHINES
DISADVANTAGES
SINGLE-PHASE FULL-WAVE CONVERTER
THREE-PHASE HALF-WAVE RECTIFIER CONTROL CIRCUIT
POWER FACTOR
THREE-PHASE HALF-CONTROLLED AND FULLY CONTROLLED BRIDGE CIRCUIT
HARMONICS AND HEATING
AC MOTOR CONTROL
CHARACTERISTIC OF PHASE-CONTROLLED AC MOTOR
Multiple Choice Questions
References
Index
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