Magnetic Bearings and Bearingless Drives

Cover......Page 1
Half Title Page......Page 2
Title Page......Page 4
Copyright......Page 5
Contents......Page 6
List of Contributors......Page 10
Foreword......Page 11
Preface......Page 13
Acknowledgements......Page 17
1.1 Magnetic bearing and motor drive......Page 20
1.2 Bearingless drives......Page 23
1.3 Definition and related technologies......Page 24
1.4 Early developments......Page 26
1.5 Bearingless structures......Page 28
1.6 Comparisons......Page 30
1.7 Winding structures......Page 32
1.8 Applications......Page 33
References......Page 34
2.1 Electro-mechanical structure and operating principles......Page 35
2.2 Electric equivalent circuit and inductance......Page 36
2.3 Stored magnetic energy and force......Page 39
2.4 Radial magnetic bearing......Page 53
2.5 Unbalance pull force......Page 59
2.6 Block diagram and mechanical system......Page 61
Reference......Page 63
3.1 Design principles in one-axis magnetic suspension......Page 64
3.2 Adjustment of PID gains......Page 71
3.3 Interference in two perpendicular axes......Page 86
3.4 Unbalance force and elimination......Page 91
3.5 Eccentric displacement......Page 97
3.6 Synchronized displacement suppression......Page 100
4.1 Two-axis system......Page 104
4.2 Four-axis and five-axis systems......Page 109
4.3 Thrust magnetic bearing and requirement of five-axis suspension......Page 113
References......Page 115
5.1 Structure and principles of power electronic circuits......Page 116
5.2 PWM operation......Page 126
5.3 Current feedback......Page 131
5.4 Current driver operating area......Page 138
5.5 Power devices and gate drive circuits......Page 141
6.1 Principles of radial force generation......Page 146
6.2 Two-pole bearingless motor......Page 150
6.3 MMF and permeance......Page 151
6.4 Magnetic potential and flux distribution......Page 154
6.5 Inductance matrix......Page 157
6.6 Radial force and current......Page 160
6.7 The dc excitation of the primitive bearingless motor......Page 164
6.8 AC excitation and revolving magnetic field......Page 166
6.9 Inductance measurements......Page 168
7. Analysis in rotational coordinates and magnetic suspension strategy for bearingless drives with 2-pole and 4-pole windings......Page 178
7.1 Vector control theory of electrical motors......Page 179
7.2 Coordinate transformation and torque regulation......Page 185
7.3 Vector control theory in bearingless motors......Page 188
7.4 Coordinate transformation from dc to ac bearingless machines......Page 192
7.5 System block diagrams of bearingless machines......Page 196
References......Page 202
8. Field orientation, VA requirement and magnetic saturation......Page 203
8.1 Misalignment of field orientation......Page 204
8.2 VA requirement......Page 209
8.3 Magnetic saturation......Page 216
References......Page 219
9.1 Structure of surface permanent magnet (SPM) rotor......Page 220
9.2 Radial suspension force and suspension winding current......Page 221
9.3 Equations of voltage and current......Page 223
9.4 Guideline for permanent magnet thickness and airgap length......Page 224
9.5 Irreversible permanent magnet demagnetization and MMF limitations of stator windings......Page 231
9.6 Control system configuration......Page 235
References......Page 238
10.1 Structure and features of an inset type of permanent magnet rotor......Page 239
10.2 Mutual interference between radial suspension forces......Page 240
10.4 Identification of suspension force parameters......Page 242
References......Page 247
11.1 BPM rotor structures......Page 248
11.2 Suspension force for unity current and permanent magnet demagnetization......Page 250
11.3 Rotor position control strategy......Page 251
References......Page 256
12.1 Torque characteristics......Page 257
12.2 Radial force characteristics......Page 260
12.3 Drive systems......Page 263
References......Page 269
13.1 Rotor structure and suspension force......Page 270
13.2 Indirect type drives......Page 276
13.3 Direct type drives......Page 283
13.4 Two-pole motor drive......Page 290
References......Page 291
14.1 Structures and principles......Page 293
14.2 Number of poles......Page 300
14.3 Drive systems......Page 303
References......Page 305
15. Switched reluctance bearingless motors......Page 306
15.1 Configuration of stator windings and principles of suspension force generation......Page 307
15.2 Derivation of inductances......Page 309
15.3 Assumption and calculation of permeances......Page 310
15.4 Theoretical formulae of suspension force and torque......Page 314
15.5 A drive system......Page 316
15.6 A feed-forward compensator for vibration reduction considering magnetic attraction force......Page 321
References......Page 326
16.1 Modified radial magnetic bearings [1,2]......Page 328
16.2 Modified motors [3–5]......Page 330
16.3 p-Pole and (p ± 2)-pole windings [9–11]......Page 332
References......Page 335
17.1 Mechanical structure......Page 337
17.2 Axial gap bearingless motors......Page 340
References......Page 347
18. Displacement sensors and sensorless operation......Page 348
18.1 Principles of displacement sensor......Page 349
18.2 Improvements in sensitivity......Page 352
18.3 Inductive and eddy current sensors......Page 355
18.4 Sensorless bearingless motor......Page 357
References......Page 361
19.1 Structure of digital controllers......Page 363
19.2 Discrete-time systems of PID controllers with the z-transform......Page 366
20.1 An induction type bearingless motor [1–4]......Page 370
20.2 A permanent magnet type bearingless motor [5,6]......Page 375
References......Page 379
21.1 Canned pumps and drives [1–4]......Page 380
21.2 Compact pumps, bubble bed reactor......Page 384
21.3 Spindle motor and semiconductor processing......Page 389
References......Page 393
Index......Page 394