Electric Motors and Drives (eBook)

Cover 1
CONTENTS 6
Preface 17
Chapter 1. ELECTRIC MOTORS 22
Introduction 22
Producing Rotation 23
Magnetic Circuits 28
Torque Production 37
Specific Loadings and Specific Output 42
Energy Conversion – Motional EMF 46
Equivalent Circuit 51
General Properties of Electric Motors 60
Review Questions 63
Chapter 2. POWER ELECTRONIC CONVERTERS FOR MOTOR DRIVES 66
Introduction 66
Voltage Control – D.C. Output from D.C. Supply 68
D.C. from A.C. – Controlled Rectification 76
A.C. from D.C. SP – SP Inversion 86
Inverter Switching Devices 93
Converter Waveforms and Acoustic Noise 96
Cooling of Power Switching Devices 96
Review Questions 100
Chapter 3. CONVENTIONAL D.C. MOTORS 103
Introduction 103
Torque Production 105
Motional E.M.F 111
D.C. motor – Steady-State Characteristics 116
Transient Behaviour – Current Surges 128
Shunt, Series and Compound Motors 132
Four-Quadrant Operation and Regenerative Braking 140
Toy Motors 145
Review Questions 147
Chapter 4. D.C. MOTOR DRIVES 154
Introduction 154
Thyristor D.C. Drives – General 155
Control Arrangements for D.C. Drives 169
Chopper-Fed D.C. Motor Drives 176
D.C. Servo Drives 180
Digitally Controlled Drives 184
Review Questions 185
Chapter 5. INDUCTION MOTORS – ROTATING FIELD, SLIP AND TORQUE 188
Introduction 188
The Rotating Magnetic Field 191
Torque Production 204
Influence of Rotor Current on Flux 212
Stator Current-Speed Characteristics 214
Review Questions 217
Chapter 6. OPERATING CHARACTERISTICS OF INDUCTION MOTORS 219
Methods of Starting Cage Motors 219
Run-up and Stable Operating Regions 227
Torque–Speed Curves – Influence of Rotor Parameters 232
Influence of Supply Voltage on Torque–Speed Curve 238
Generating and Braking 239
Speed Control 242
Power Factor Control and Energy Optimisation 246
Single-Phase Induction Motors 248
Size Range 253
Review Questions 254
Chapter 7. INDUCTION MOTOR EQUIVALENT CIRCUIT 257
Introduction 257
Similarity Between Induction Motor and Transformer 259
The Ideal Transformer 261
The Real Transformer 269
Development of the Induction Motor Equivalent Circuit 279
Properties of Induction Motors 282
Performance Prediction – Example 284
Approximate Equivalent Circuits 288
Measurement of Parameters 295
Equivalent Circuit Under Variable-Frequency Conditions 295
Review Questions 298
Chapter 8. INVERTER-FED INDUCTION MOTOR DRIVES 300
Introduction 300
Torque–Speed Characteristics – Constant V/f Operation 307
Control Arrangements for Inverter-Fed Drives 311
Vector (Field-Oriented) Control 317
Cycloconverter Drives 321
Review Questions 324
Chapter 9. STEPPING MOTORS 326
Introduction 326
Principle of Motor Operation 332
Motor Characteristics 339
Steady-State Characteristics – Ideal (Constant-Current) Drive 345
Drive Circuits and Pull-Out Torque–Speed Curves 349
Transient Performance 356
Review Questions 359
Chapter 10. SYNCHRONOUS, BRUSHLESS D.C. AND SWITCHED RELUCTANCE DRIVES 361
Introduction 361
Synchronous Motors 362
Controlled-Speed Synchronous Motor Drives 373
Brushless D.C. Motors 378
Switched Reluctance Motor Drives 379
Review Questions 384
Chapter 11. MOTOR/DRIVE SELECTION 387
Introduction 387
Power Range for Motors and Drives 387
Load Requirements – Torque–Speed Characteristics 390
General Application Considerations 396
Review Questions 400
APPENDIX: INTRODUCTION TO CLOSED–LOOP CONTROL 402
Reasons for Adopting a Simplified Approach 402
Closed-Loop (Feedback) Systems 403
Steady-State Analysis of Closed-Loop Systems 407
Importance of Loop Gain – Example 411
Steady-State Error – Integral Control 413
PID Controller 415
Stability 417
Disturbance Rejection – Example Using D.C. Machine 418
Further Reading 421
Answers to Numerical Review Questions 422
Index 425