Practical Variable Speed Drives and Power Electronics (eBook)

Cover 1
Contents 6
1. Introduction 13
1.1 The need for variable speed drives 1
1.2 Fundamental principles 1
1.3 Torque-speed curves for variable speed drives 1
1.4 Types of variable speed drives 1
1.5 Mechanical variable speed drive methods 1
1.6 Hydraulic variable speed drives methods 1
1.7 Electromagnetic or 'Eddy Current' coupling 1
1.8 Electrical variable speed drive methods 1
2. 3-Phase AC induction motors 48
2.1 Introduction 1
2.2 Basic construction 1
2.3 Principles of operation 1
2.4 The equivalent circuit 1
2.5 Electrical and mechanical performance 1
2.6 Motor acceleration 1
2.7 AC induction generator performance 1
2.8 Efficiency of electric motors 1
2.9 Rating of AC induction motors 1
2.10 Electric motor duty cycles 1
2.11 Cooling and ventilation of electric motors (IC) 1
2.12 Degree of protection of motor enclosures (IP) 1
2.13 Construction and mounting of AC induction motors 1
2.14 Anti-condensation heaters 1
2.15 Methods of starting AC induction motors 1
2.16 Motor selection 1
3. Power electronic converters 80
3.1 Introduction 1
3.2 Definitions 1
3.3 Power diodes 1
3.4 Power thyristors 1
3.5 Commutation 1
3.6 Power electronic rectifiers (AC/DC converters) 1
3.7 Gate commutated inverters (DC/AC converters) 1
3.8 Gate controlled power electronic devices 1
3.9 Other pwoer converter circuit components 1
4. Electromagnetic compatibility (EMC) 126
4.1 Introduction 1
4.2 The sources of electromagnetic interference 1
4.3 Harmonics generated on the supply side of AC converters 1
4.4 Power factor and displacement factor 1
4.5 Voltages and current on the motor side of PWM inverters 1
5. Protection of AC converters and motors 152
5.1 Introduction 1
5.2 AC frequency converter protection circuits 1
5.3 Operator information and fault diagnostics 1
5.4 Electric motor protection 1
5.5 Thermal overload protection „ current sensors 1
5.6 Thermal overload protection „ direct temperature sensing 1
6. Control systems for AC variable speed drives 168
6.1 The overall control system 1
6.2 Power supply to the control system 1
6.3 The DC bus charging control system 1
6.4 The PWM rectifier for AC converters 1
6.5 Variable speed drive control loops 1
6.6 Vector control for AC drives 1
6.7 Current feedback in AC variable speed drives 1
6.8 Speed feedback from the motor 1
7. Selection of AC converters 190
7.1 Introduction 1
7.2 The basic selection procedure 1
7.3 The loadability of converter fed squirrel cage motors 1
7.4 Operation in the constant power region 1
7.5 The nature of the machine load 1
7.6 The requirements for starting 1
7.7 The requirements for stopping 1
7.8 Control of speed, torque and accuracy 1
7.9 Selecting the correct size of motor and converter 1
7.10 Summary of the selection procedures 1
8. Installation and commissioning 221
8.1 General installation and environmental requirements 1
8.2 Power supply connection and earthing requirements 1
8.3 Start/stop control of AC drives 1
8.4 Installing AC converters into metal enclosures 1
8.5 Control wiring for variable speed drives 1
8.6 Commissioning variable speed drives 1
9. Special topics and new developments 241
9.1 Soft-switching 1
9.2 The matrix converter 1
Appendix A: Motor protection „ direct temperature sensing 1
A.1 Introduction 1
A.2 Microtherm (thermostat) 1
A.3 Thermistor sensors and thermistor protection relays 1
A.4 Thermocouple 1
A.5 Resistance temperature detector (RTD) 1
Appendix B: Current measurement transducers 1
B.1 Current shunt 1
B.2 Principle of the Hall effect sensor 1
Appendix C: Speed measurement transducers 1
C.1 Analog speed transducers 1
C.2 Digital rotary speed and position transducers 1
Appendix D: International and national standards 1
D.1 Introduction 1
D.2 International standards 1
D.3 European standards 1
D.4 United States of America standards 1
D.5 National standards 1
D.6 South African standards 1
Appendix E: Glossary of common terms used with AC variable speed drives 1
Index 1