Brushless_Permanent_Magnet_Motor_Design(1).pdf
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1、Brushless Permanent Magnet Motor Design Second Edition Dr.Duane Hanselman Electrical and Computer Engineering University of Maine Orono,ME 04469 USA MAGNA PHYSICS PUBLISHING Preface to the Second Edition Preface to the First Edition Chapter 1 Basic Concepts 1.1 Scope 1.2 Shape 1.3 Torque 1.4 Motor A
2、ction 1.5 Magnet Poles and Motor Phases 1.6 Poles,Slots,Teeth,and Yokes 1.7 Mechanical and Electrical Measures 1.8 Motor Size 1.9 Units 1.10 Summary Chapter 2 Magnetic Modeling 2.1 Magnetic Circuit Concepts Basic Relationships Magnetic Field Sources Air Gap Modeling Slot Modeling Example 2.2 Magneti
3、c Materials Permeability Ferromagnetic Materials Core Loss Permanent Magnets Permanent Magnet Magnetic Circuit Model 2.3 Example 2.4 Summary Chapter 3 Electrical and Mechanical Relationships 3.1 Flux Linkage and Inductance Self inductance 45 Mutual Inductance 46 Mutual Flux Due to a Permanent Magnet
4、 49 3.2 Induced voltage 50 Faradays Law 50 Example 51 3.3 Energy and Coenergy 53 Energy and Coenergy in Singly-Excited Systems 53 Energy and Coenergy in Doubly-Excited Systems 55 Coenergy in the Presence of a Permanent Magnet 56 3.4 Force,Torque and Power 56 Basic Relationships 56 Fundamental Implic
5、ations 57 Torque From a Macroscopic Viewpoint 58 Force From a Microscopic Viewpoint 61 Reluctance and Mutual Torque 62 Example 63 3.5 Summary 64 Chapter 4 Brushless Motor Fundamentals 67 4.1 Assumptions 67 Rotational Motion 67 Surface-Mounted Magnets 67 4.2 Fundamental Concepts 68 Magnetic Circuit M
6、odel 68 Magnetic Circuit Solution 71 Flux Linkage 74 Back EMF and Torque 76 Multiple Coils 78 4.3 Multiple Phases 80 4.4 Design Variations 82 Fractional Pitch Coils 82 Fractional Pitch Magnets 84 Fractional Slot Motor 86 4.5 Coil Resistance 90 4.6 Coil Inductance 94 Air Gap Inductance 95 Slot Leakag
7、e Inductance 96 End Turn Inductance 98 4.7 Series and Parallel Connections 100 4.8 Armature Reaction 103 4.9 Slot Constraints 104 Slot Fill Factors 104 Slot Resistance 105 Wire Gage Relationships 106 Constancy of Ni 107 4.10 Torque Constant,Back EMF Constant,and Motor Constant 108 4.11 Torque per Un
8、it Rotor Volume 110 4.12 Cogging Torque 111 4.13 Summary 115 Chapter 5 Motor Design Possibilities 117 5.1 Radial Flux Motors 117 Inner Rotor 117 Outer Rotor 120 5.2 Axial Flux Motors 121 5.3 Li near Mo tor s 123 5.4 Summary 124 Chapter 6 Windings 125 6.1 Assumptions 125 6.2 Coil Span 126 6.3 Valid P
9、ole and Slot Combinations 127 6.4 Winding Layout 129 Example 131 Example 134 Winding Layout Procedure 137 6.5 Coil Connections 139 6.6 Winding Factor 140 6.7 Inductance Revisited 143 Single Tooth Coil Equivalence 144 Air Gap Inductance 144 Slot Leakage Inductance 148 6.8 Summary 150 Chapter 7 Magnet
10、ic Design 7.1 Air Gap Magnetic Field Distribution 151 152 Air Gap Region Solution 153 Magnet Region Solution 153 Symmetry 154 7.2 Influence of Stator Slots 154 7.3 Tooth Flux 158 7.4 Stator Yoke Flux 162 7.5 Influence of Skew 165 7.6 Influence of Ferromagnetic Material 169 7.7 Back EMF 173 7.8 Slotl
11、ess Motor Construction 176 Concentrated Winding 176 Sinusoidally-Distributed Winding 180 7.9 Summary 181 Chapter 8 Electrical Control 183 8.1 Fundamentals of Torque Production 183 8.2 Brushless DC Motor Drive 185 Ideal Torque Production 185 Motor Constant 187 Torque Ripple 187 8.3 AC Synchronous Mot
12、or Drive 188 Ideal Torque Production 188 Motor Constant 189 Torque Ripple 189 8.4 General Drive 193 Ideal Torque Production 193 Torque Ripple 195 Motor Constant 195 8.5 Motor Drive Topologies 196 Half Bridge 196 Full H-Bridge 196 Y-Connection 198 zl-Connection 200 8.6 Summary 201 Chapter 9 Performan
13、ce 203 9.1 Motor Constant 203 General Sizing 203 Motor Constant Maximization 206 9.2 Cogging Torque Relationships 209 9.3 Radial Force Relationships 214 9.4 Core Losses 217 Basic Concepts 217 Core Loss Modeling 219 Application to Motor Design 222 Conclusion 223 9.5 AC Winding Resistance 223 9.6 Summ
14、ary 226 Chapter 10 Examples 229 Common Characteristics 229 Presented Results 230 Notes 231 Two Pole Motors 232 Four Pole Motors 234 Six Pole Motors 250 Eight Pole Motors 258 Ten Pole Motors 278 Twelve Pole Motors 294 Fourteen Pole Motors 300 Sixteen Pole Motors 312 Twenty Pole Motors 320 Twenty-Four
15、 Pole Motors 326 Thirty-Two Pole Motors 330 Appendix A Fourier Series 335 A.l Definition 335 A.2 Coefficients 336 A.3 Symmetry Properties 337 A.4 Mathematical Operations 337 Addition 338 Scalar Multiplication 338 Function Product 338 Phase Shift 338 Differentiation 339 Mean Square Value and RMS 339
16、A.5 Computing Coefficients 339 Procedure 340 A.6 Summary 341 Appendix B Magnetic Field Distributions in Polar Coordinates 343 B.l Problem Formulation 343 B.2 Polar Coordinate Application 345 B.3 Air Gap Region Solution 348 B.4 Magnet Region Solution 350 B.5 Summary 352 B.6 Magnetization Profiles 353
17、 Radial Magnetization 354 Parallel Magnetization 355 Radial Sinusoidal Amplitude Magnetization 356 Sinusoidal Angle Magnetization 356 B.7 Examples 357 B.8 Summary 360 Appendix C Magnetic Field Distributions in Rectangular Coordinates 361 C.l Rectangular Coordinate Application 362 Single Magnet and S
18、ingle Air Gap Case 363 Two Magnet,Single Air Gap Case 364 One Magnet,Two Air Gap Case 365 C.2 Magnetization Profile 366 C.3 Summary 366 Appendix D Symbols,Units,and Abbreviations 367 Appendix E Glossary 373 Bibliography 381 Books 381 Articles 384 Index 387 This chapter develops a number of basic mot
19、or concepts in a way that appeals to your intuition.In doing so,the concepts are more likely to make sense,especially when these concepts are used for motor design in later chapters.Many of the con-cepts presented here apply to most motor types since all motors are constructed of similar materials a
20、nd all produce the same output,namely torque.1.1 Scope This text covers the analysis and design of rotational brushless permanent magnet(PM)motors.Brushless DC,PM synchronous,and PM step motors are all brushless permanent magnet motors.These specific motor types evolved over time to satisfy differen
21、t application niches,but their operating principles are essentially identical.Thus,the material presented in this text is applicable to all three of these motor types,with particular emphasis given to brushless DC and PM synchronous motors.To put these motor types into perspective,it is useful to sh
22、ow where they fit in the overall classification of electric motors as shown in Fig.1-1.The other motors shown in the figure are not considered in this text.Their operating principles can be found in a number of other texts.Brushless DC motors are typically characterized as having a trapezoidal back
23、elec-tromotive force(EMF)and are typically driven by rectangular pulse currents.This mimics the operation of brush DC motors.From this perspective,the name brush-less DC fits even though it is an AC motor.PM synchronous motors differ from brushless DC motors in that they typically have a sinusoidal
24、back EMF and are driven by sinusoidal currents.Step motors in general have high pole counts and therefore require many periods of excitation for each shaft revolution.Even though they can be driven like other synchronous motors,they are typically driven with cur-rent pulses.Step motors are typically
25、 used in low cost,high volume,position,-cqntrol applications where the cost of position feedback cannot be justified.Figure 1.1 A classification of motors.The most common motor shape is cylindrical as shown in Fig.1-2a.This motor shape and all others contain two primary parts.The nonmoving or statio
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