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 law, 5 1.2.4.2 Kirchhoff s Voltage law, 6 1.2.5 Thevenin Theorem, 7 1.3 AC Circuit Analysis, 9 1.3.1 Root Mean Square Value, 9 1.3.2 RMS Value of a Sinusoidal Current, 10 1.4 Three-phase System, 11 v^ 1.5 Naming of Phases and Phase Sequence, 12 1.6 Star or Y-connection, 13 1.7 Voltage and Current Relations for Y-connected System, 14 1.8 Delta or Mesh Connection, 17 1.9 Voltage and Current Relations for Delta Connection, 18 1.10 Balanced and Unbalanced Loads, 20 1.11 Y-connected Generator and Y-connected Load, 21 1.12 Y-connected Generator and Delta-connected Load, 24 1.13 Three-phase Power, 27 1.14 Measurement of Three-phase Power, 30 1.15 Power Factor Measurement, 30 1.16 Power Factor, 33 1.17 Power Factor Correction, 33 Exercise Problems, 37
xi 3.14 Transformer Losses, 104 3.14.1 Iron Loss, 105 3.14.2 Copper Loss, 105 3.15 Condition for Maximum Efficiency, 106 3.16 All-day Efficiency, 109 3.17 Transformer Tests, 110 3.17.1 Open Circuit Test, 110 3.17.2 Short Circuit Test, 111 3.18 Autotransformer, 113 3.19 Parallel Operation of Single-phase Transformer, 116 3.19.1 Equal Voltage Ratio, 116 3.19.2 Unequal Voltage Ratio, 117 3.20 Three-phase Transformer, 119 3.21 Three-phase Transformer Connections, 120 3.21.1 Wye-Wye Connection, 121 3.21.2 Wye-Delta Connection, 121 3.21.3 Delta-Wye Connection, 122 3.21.4 Delta-Delta Connection, 123 3.22 Transformer Cooling, 126 3.23 Instrument Transformers, 126 3.24 Standard Symbols and Reactance Diagram, 127 3.25 Per Unit System, 129 3.25.1 Single-phase System, 130 3.25.2 Three-phase System, 130 Exercise Problems, 135 Chapter 4 Direct Current Generators 142 4.1 Introduction, 142 4.2 Electromagnetic Induction, 142 4.3 Motional Voltage. 143 4.4 Lenz's Law, 145 4.5 Working Principle of DC Generator, 146 4.6 Construction of a DC Generator, 148 4.7 Armature Windings, 148 4.8 Induced EMF of a DC Generator, 150 4.9 Classification of a DC Generator, 153 4.9.1 Separately Excited DC Generator, 153 4.9.2 Self Excited DC Generator, 154 4.9.2.1 Series Generator, 155 4.9.2.2 Shunt Generator, 155 4.9.2.3 Compound Generator, 156 4.10 Saturation Curve of a DC Generator, 161 4.11 Generator Buildup Process, 162 4.12 Reasons for Failure of Voltage Buildup, 162 4.13 Filed Circuit Resistance Lines, 163 4.14 Theory of Commutation, 164 4.15 Armature Reaction, 165
xu 4.16 Demagnetizing and Cross Magnetizing, 167 4.17 Cancellation of Armature Reaction, 169 4.18 Characteristics of a Series Generator, 171 4.19 Characteristics of a Shunt Generator, 171 4.20 Characteristics of a Compound Generator, 172 4.21 AppHcation of a DC Generator, 173 4.22 Voltage Regulation of a DC Generator, 174 4.23 Losses of a DC Generator, 174 4.24 Efficiency of a DC Generator, 175 Exercise Problems, 178 Chapter 5 Direct Current Motors 181_ 5.1 Introduction, 181 5.2 Working Principle, 181 :5i3 Back EMF, 182 5.4 Necessity of Back EMF, 183 5.5 Classification of a DC Motor, 184 5.5.1 Shunt Motor, 183 5.5.2 Series Motor, 185 5.5.3 Compound Motor, 185 5.5.3.1 Short Shunt Compound Motor, 186 5.5.3.2 Long Shunt Compound Motor, 186 5.6 Mechanical Power of a DC Motor, 187 5.7 Torque of a DC Motor, 190 5.7.1 Armature Torque, 190 5.7.2 Shaft Torque, 191 5.8 Speed of a DC Motor, 192 5.9 Speed Regulation of a DC Motor, 195 5.10 Losses in a DC Motor, 196 5.11 Efficiency of a DC Motor, 196 >>-Us' 5.12 Classification of a DC Motor, 199 5.13 Characteristics of a Shunt Motor, 200 5.14 Characteristics of a Series Motor, 201 5.15 Characteristics of a Cumulative Compound Motor, 203 5.16 Comparison between Generator and Motor, 204 5.17 Application of DC Motors, 205 Exercise Problems, 206 Chapter 6 Control and Starting of a DC Motors 209 6.1 Introduction, 209 6.2 Speed Controlling Parameters, 209 6.3 Flux Control Method, 210 6.4 Armature Control Method, 211 6.5 Armature Voltage Control Method, 213 6.6 Speed Control of a Series Motor, 214
xiii 6.7 Ward Leonard System, 218 6.8 Semiconductor Diode, 219 6.9 Half Wave Rectifier, 220 6.10 Full Wave Rectifier, 222 6.10.1 Centre Tap Full Wave Rectifier, 222 6.10.2 Bridge Type Full Wave Rectifier, 223 6.11 Speed Control by Thyristor and Diode, 226 6.12 Braking of a DC Motor, 226 6.12.1 Plugging, 227 6.12.2 Dynamic Braking, 228 6.12.3 Regenerative Braking, 229 6.13 DC Motor Starter, 229 6.14 Three-point Starter, 230 6.15 Four-point Starter, 230 6.16 Grading of Starting Resistance, 231 Exercise Problems, 237 Chapter 7 Ttiree-pliase Induction Motor 239 7.1 Introduction, 239 7.2 r instruction, 239 7.3 Working Principle, 241 7.4 Rotating Field, 242 7.5 Synchronous Speed and Slip Speed, 245 7.6 Rotor Frequency, 246 7.7 Rotor Voltage and Rotor Reactance, 247 7.8 Rotor Torque, 248 7.9 Starting Torque, 248 7.10 Running Torque, 251 7.11 Relationships between Torques, 252 7.12 Equivalent Circuit, 255 7.12.1 Transformer Model of an Induction Motor, 255 7.12.2 Rotor Circuit Model, 255 7.12.3 IEEE Recommended Equivalent Circuit, 257 7.12.4 Thevenin Equivalent Circuit, 257 7.13 Power Relationships, 258 7.14 Approximate Equivalent Circuit, 261 7.15 Condition for Maximum Mechanical Power, 262 7.16 Power Stages, 264 7.17 Torque-Slip Characteristics, 266 7.18 Linear Induction Motor, 268 7.19 Classification of an Induction Motor by Properties, 269 Exercise Problems, 270 Chapter 8 Starting, Control and Testing of an Induction Motor 272 8.1 Introduction, 272
xiv 8.2 Direct Starting, 272 8.3 Autotransformer Starter, 273 8.4 Star-Delta Starter, 275 8.5 Simple Magnetic Starter, 277 8.6 Forward-Reverse Starter, 278 8.7 Cogging and Crawling, 279 8.8 Double Squirrel Cage Motor, 279 8.9 Determination of Equivalent Circuit Parameters, 283 8.9.1 Blocked Rotor Test, 283 8.9.2 No-load Test, 285 8.10 Speed Control of Induction Motor, 288 8.10.1 Frequency Control, 288 8.10.2 Pole Changing, 288 8.10.3 Cascade Arrangements, 288 Exercise Problems, 291 Chapter 9 Synchronous Generator 292 9.1 Introduction, 292 9.2 Construction, 293 9.3 Pole and Frequency, 294 9.4 Working Principle, 295 9.5 Full Pitch and Short Pitch Windings, 296 9.6 Pitch or Chording Factor, 298 9.7 Distribution Factor, 301 9.8 Effect of Harmonics on Pitch and Distribution Factors, 303 9.9 EMF Equation of an Alternator, 304 9.10 Equivalent Circuit of Synchronous Generator, 308 9.11 Phasor Diagrams and Voltage Regulation, 310 9.11.1 Unity Power Factor Phasor Diagram, 310 9.11.2 Lagging Power Factor Phasor Diagram, 311 9.11.3 Leading Power Factor Phasor Diagram, 311 9.11.4 Voltage Regulation, 311 9.12 Tests of a Synchronous Generator, 312 9.12.1 Determination of a Resistance, 312 9.12.2 Open Circuit Test, 313 9.12.3 Short Circuit Test, 313 9.13 Power and Torque Expressions, 315 9.14 Salient Pole Synchronous Generator, 318 9.15 Power of a Salient Pole Generator, 319 9.16 Parallel Operation of an Alternator, 322 Exercise Problems, 326 Chapter 10 Synchronous Motor 328 10.1 Introduction, 328 10.2 Construction, 328
XV 0.3 Working Principle, 329 0.4 Starting of Synchronous Motor, 329 0.5 Equivalent Circuit, 330 0.6 Phasor Diagrams, 331 10.6.1 Unity Power Factor, 331 10.6.2 Lagging Power Factor, 331 10.6.3 Leading Power Factor, 332 0.7 Synchronous Impedance Diagrams, 333 0.8 Effect ofdifferent Field Excitations, 333 10.8.1 Normal Excitation, 333 10.8.2 Under Excitation, 334 10.8.3 Over Excitation, 334 0.9 Power for Cylindrical Rotor, 337 0.10 Various Conditions of Power, 340 0.11 Phasor Diagrams for Salient Pole Motor, 344 0.12 Power Expression for Salient Pole Motor, 345 0.13 V-curves of a Synchronous Motor, 347 0.14 Power Factor Correction, 347 0.15 Applications of Synchronous Motor, 348 0.16 Comparison of Synchronous Motor and Induction Motor, 348 Exercise Problems, 349 hapter 11 Single-phase Motors 351 11.1 Introduction, 351 11.2 Construction and Synchronous Speed, 351 11.3 Double Revolving Field Theory, 352 11.3.1 Slip of a Single-phase Motor, 354 11.4 Equivalent Circuit, 355 11.5 Classification of a Single-phase Motor, 358 11.6 Starting of Single-phase Motors, 359 11.6.1 Split Phase Motor, 359 11.6.2 Capacitor Start Motor, 360 11.6.3 Capacitor Start and Capacitor Run Motor, 361 11.6.4 Capacitor Run Motor, 362 11.6.5 Shaded Pole Motor, 363 11.7 AC Series Motor, 365 11.8 Reluctance and Hysteresis Motors, 365 11.8.1 Reluctance Motor, 365 11.8.2 Hysteresis Motor, 366 11.9 Testing of a Single-phase Motor, 367 11.9.1 Blocked Rotor Test, 367 11.9.2 No-load Test, 368 11.10 Stepper Motor, 371 11.11 Classification of Stepper Motor, 371 11.11.1 Variable-reluctance Stepper Motor, 371 11.11.2 Permanent-magnet Stepper Motor, 372
xvi 11.11.3 Hybrid Stepper Motor, 373 Exercise Problems, 374 References, 375 Appendix A Mathematical Formulas, 377 Appendix B Answers to Drill and Exercise Problems, 380 Index, 396