Practical Variable Speed Drives and Power Electronics

Cover......Page 1
Half Title Page......Page 2
Titles in the series......Page 3
Title Page......Page 4
Copyright......Page 5
Preface......Page 6
Contents......Page 8
1.1 The need for variable speed drives......Page 13
1.2 Fundamental principles......Page 14
1.3 Torque-speed curves for variable speed drives......Page 19
1.4 Types of variable speed drives......Page 23
1.5 Mechanical variable speed drive methods......Page 25
1.6 Hydraulic variable speed drives methods......Page 26
1.7 Electromagnetic or 'Eddy Current' coupling......Page 28
1.8 Electrical variable speed drive methods......Page 32
2.1 Introduction......Page 48
2.2 Basic construction......Page 49
2.3 Principles of operation......Page 51
2.4 The equivalent circuit......Page 53
2.5 Electrical and mechanical performance......Page 57
2.6 Motor acceleration......Page 60
2.7 AC induction generator performance......Page 62
2.8 Efficiency of electric motors......Page 63
2.9 Rating of AC induction motors......Page 64
2.10 Electric motor duty cycles......Page 66
2.11 Cooling and ventilation of electric motors (IC)......Page 72
2.12 Degree of protection of motor enclosures (IP)......Page 74
2.13 Construction and mounting of AC induction motors......Page 75
2.14 Anti-condensation heaters......Page 77
2.16 Motor selection......Page 78
3.2 Definitions......Page 80
3.3 Power diodes......Page 83
3.4 Power thyristors......Page 85
3.5 Commutation......Page 88
3.6 Power electronic rectifiers (AC/DC converters)......Page 89
3.7 Gate commutated inverters (DC/AC converters)......Page 106
3.8 Gate controlled power electronic devices......Page 116
3.9 Other pwoer converter circuit components......Page 124
4.1 Introduction......Page 126
4.2 The sources of electromagnetic interference......Page 128
4.3 Harmonics generated on the supply side of AC converters......Page 130
4.4 Power factor and displacement factor......Page 141
4.5 Voltages and current on the motor side of PWM inverters......Page 143
5.2 AC frequency converter protection circuits......Page 152
5.3 Operator information and fault diagnostics......Page 160
5.4 Electric motor protection......Page 162
5.5 Thermal overload protection — current sensors......Page 164
5.6 Thermal overload protection — direct temperature sensing......Page 165
6.1 The overall control system......Page 168
6.2 Power supply to the control system......Page 169
6.3 The DC bus charging control system......Page 171
6.4 The PWM rectifier for AC converters......Page 173
6.5 Variable speed drive control loops......Page 175
6.6 Vector control for AC drives......Page 179
6.7 Current feedback in AC variable speed drives......Page 186
6.8 Speed feedback from the motor......Page 188
7.1 Introduction......Page 190
7.2 The basic selection procedure......Page 191
7.3 The loadability of converter fed squirrel cage motors......Page 192
7.4 Operation in the constant power region......Page 195
7.5 The nature of the machine load......Page 196
7.6 The requirements for starting......Page 206
7.7 The requirements for stopping......Page 208
7.9 Selecting the correct size of motor and converter......Page 215
7.10 Summary of the selection procedures......Page 217
8.1 General installation and environmental requirements......Page 221
8.2 Power supply connection and earthing requirements......Page 223
8.3 Start/stop control of AC drives......Page 226
8.4 Installing AC converters into metal enclosures......Page 228
8.5 Control wiring for variable speed drives......Page 234
8.6 Commissioning variable speed drives......Page 239
9.1 Soft-switching......Page 241
9.2 The matrix converter......Page 243
A.2 Microtherm (thermostat)......Page 245
A.3 Thermistor sensors and thermistor protection relays......Page 246
A.4 Thermocouple......Page 250
A.5 Resistance temperature detector (RTD)......Page 252
B.1 Current shunt......Page 256
B.2 Principle of the Hall effect sensor......Page 257
C.1 Analog speed transducers......Page 260
C.2 Digital rotary speed and position transducers......Page 262
D.2 International standards......Page 274
D.4 United States of America standards......Page 275
D.6 South African standards......Page 276
Appendix E: Glossary of common terms used with AC variable speed drives......Page 278
Index......Page 289