Noise of Polyphase Electric Motors

dk3193_fm......Page 1
Table of Contents......Page 14
Preface......Page 10
Authors......Page 12
Symbols and Abbreviations......Page 20
Table of Contents......Page 0
1.2 Sound waves......Page 25
1.3.1 Electromagnetic sources of noise......Page 29
1.4 Energy conversion process......Page 31
1.5 Noise limits and measurement procedures for electrical machines......Page 33
1.6 Deterministic and statistical methods of noise prediction......Page 37
1.7 Economical aspects......Page 41
1.8 Accuracy of noise prediction......Page 42
2.1 Construction of induction motors......Page 44
2.2 Construction of permanent magnet synchronous brushless motors......Page 46
2.3 A.C. stator windings......Page 48
2.4.1 Single-phase stator winding......Page 51
2.4.2 Three-phase stator winding......Page 55
2.4.3 Polyphase stator winding......Page 56
2.5 Rotor magnetic field......Page 59
2.6.1 Effect of slots......Page 60
2.6.2 Effect of eccentricity......Page 63
2.6.3 Effect of magnetic saturation......Page 66
2.6.4 Effect of rotor saliency......Page 67
2.7.1 Production of radial magnetic forces......Page 68
2.7.2 Amplitude of magnetic pressure......Page 71
2.7.3 Deformation of the stator core......Page 72
2.7.4 Frequencies and orders of magnetic pressure......Page 73
2.7.5 Radial forces in synchronous machines with slotted stator......Page 74
2.7.6 Frequencies of vibration and noise......Page 77
2.8.2 Magnetostriction......Page 81
2.8.4 FEM model......Page 85
3.1 Generation of higher time harmonics......Page 88
3.2 Analysis of radial forces for nonsinusoidal currents......Page 89
3.2.1 Stator and rotor magnetic flux density......Page 90
3.2.2 Stator harmonics of the same number......Page 91
3.2.3 Interaction of stator and rotor harmonics......Page 92
3.2.6 Interaction of stator harmonics of different numbers......Page 93
3.3.1 Asynchronous torques......Page 94
3.3.2 Pulsating torques......Page 95
3.5 Influence of the switching frequency of an inverter......Page 96
3.6 Noise reduction of inverter-fed motors......Page 98
4.1 Analytical methods of instantaneous torque calculation......Page 100
4.2 Numerical methods of instantaneous torque calculation......Page 101
4.3 Electromagnetic torque components......Page 102
4.5 Higher harmonic torques of induction motors......Page 103
4.6 Cogging torque in permanent magnet (PM) brushless motors......Page 104
4.6.1 Air gap magnetic flux density......Page 105
4.6.2 Calculation of cogging torque......Page 107
4.6.3 Simplified cogging torque equation......Page 110
4.6.4 Influence of eccentricity......Page 111
4.6.5 Calculation and comparison with measurements......Page 115
4.7 Torque Ripple due to distortion of EMF and current waveforms in PM brushless motors......Page 117
4.8 Tangential forces vs. radial forces......Page 122
4.9.1 Slotless windings......Page 125
4.9.3 Shaping stator slots......Page 126
4.9.8 Selection of PM width......Page 127
4.9.10 Creating magnetic circuit asymmetry......Page 128
5.1 Forced vibration......Page 129
5.2 Simplified calculation of natural frequencies of the stator system......Page 132
5.3.1 Natural frequency of the stator core......Page 134
5.3.2 Natural frequency of a frame with end bells......Page 136
5.3.3 Natural frequency of a stator core–frame system......Page 137
5.3.4 Effect of the stator winding and teeth......Page 138
5.3.5 Analytical calculation of natural frequencies for a stator core-winding-frame system......Page 139
5.4.1 FEM modeling......Page 142
5.4.2 Comparison of analytical calculations with the FEM......Page 144
6.1 Sound radiation efficiency......Page 148
6.2 Plane radiator......Page 150
6.2.2 Finite plates in bending motion......Page 154
6.3 Infinitely long cylindrical radiator......Page 162
6.4 Finite length cylindrical radiator......Page 166
6.4.1 Acoustically thin shells......Page 168
6.4.2 Acoustically thick shells......Page 170
6.4.3 Modal radiation efficiencies of acoustically thick shells......Page 175
6.4.4 Modal averaged radiation efficiency......Page 178
6.4.5 Validity of using an infinite length model......Page 182
6.4.6 Effects of boundary conditions on the radiation efficiency......Page 185
6.5 Calculations of sound power level......Page 187
6.5.1 Sound power radiated from a stator......Page 188
6.5.2 Total sound power of an induction motor......Page 189
6.5.3 Permanent magnet synchronous motors......Page 192
7.1 Mechanical noise due to shaft and rotor irregularities......Page 196
7.2.1 Rolling bearings......Page 197
7.3 Noise due to toothed gear trains......Page 201
7.4 Aerodynamic noise......Page 202
7.5 Mechanical noise generated by the load......Page 205
8.1 Measuring system and transducers......Page 207
8.2.2 The sound pressure sensor–condenser microphone......Page 209
8.2.3 Sound level meter......Page 213
8.2.4 Acoustic calibrator......Page 216
8.3.1 Effect of the operator on measurement results......Page 217
8.3.4 Measurements of ambient sound pressure levels......Page 218
8.3.5 Coreections for background sound during source measurements......Page 219
8.4 Vibration measurements......Page 220
8.4.1 Theory of operation of vibration-measuring transducer......Page 221
8.4.2 Characteristics of piezoelectric accelerometers......Page 227
8.4.3 Other vibration transducers......Page 231
8.5 Frequency analyzers......Page 233
8.6 Sound power and sound pressure......Page 234
8.7.1 Determination of sound power in an anechoic/ semianechoic room......Page 235
8.7.2 Reverberation room......Page 236
8.8.2 Theoretical background......Page 237
8.8.3 Sound intensity probe......Page 239
8.8.5 Error considerations......Page 241
8.8.6 Dynamic capability and pressure-intensity index......Page 243
8.9.1 Background......Page 244
8.9.2 Acoustic tests on an induction motor......Page 246
9.1 Introduction......Page 251
9.2 FEM model for radial magnetic pressure......Page 252
9.2.1 Induction motor......Page 253
9.2.2 Permanent magnet synchronous motor......Page 257
9.3 FEM for structural modeling......Page 259
9.4.1 Governing equation and boundary conditions......Page 263
9.4.2 FEM......Page 267
9.4.4 Radiating sphere......Page 268
9.4.5 Application to the prediction of radiated acoustic power from an inverter-fed induction motor......Page 270
9.5 Discussion......Page 275
10.1 Introduction......Page 277
10.2.1 Two Coupled oscillators......Page 279
10.2.2 Three series coupled oscillators......Page 281
10.2.3 Energy exchange between groups of oscillators......Page 284
10.3.1 General SEA equations......Page 287
10.3.2 SEA model establishment......Page 289
10.3.3 SEA parameters......Page 292
10.3.4 Limitations of SEA......Page 298
10.4 Experimental SEA......Page 301
10.4.1 General theory......Page 302
10.4.2 Recent developments......Page 305
10.5 Application to electrical motors......Page 310
10.5.1 Subsystems of a motor structure......Page 311
10.5.2 Internal and coupling loss factors......Page 312
10.5.3 Input power to the stator......Page 313
10.5.4 Sound power radiated from the motor structure......Page 315
11.1.1 Foundation......Page 320
11.1.2 Principles of vibration and shock isolation......Page 322
11.1.4 Shaft alignment......Page 325
11.2 Standard methods of noise reduction......Page 326
11.3.1 Principles of active noise control......Page 330
11.3.2 Induction motor acoustic noise reduction......Page 332
11.3.3 Active vibration isolation......Page 334
A.1 Sound field variables and wave equations......Page 337
A.2 Sound radiation from a point source......Page 339
A.3 Decibel levels and their calculations......Page 341
A.4 Spectrum analysis......Page 343
B.1 Permeance calculation......Page 344
B.2 Eccentricity effect......Page 345
Appendix C Magnetic Saturation......Page 350
D.1 A mass–spring–damper oscillator......Page 353
D.2 Lumped parameter systems......Page 355
D.3 Continuous systems......Page 358
Bibliography......Page 362