2nd Edition

Mechanical Design and Manufacturing of Electric Motors

By Wei Tong Copyright 2022
    986 Pages 706 B/W Illustrations
    by CRC Press

    This Second Edition of Mechanical Design and Manufacturing of Electric Motors provides in-depth knowledge of design methods and developments of electric motors in the context of rapid increases in energy consumption, and emphasis on environmental protection, alongside new technology in 3D printing, robots, nanotechnology, and digital techniques, and the challenges these pose to the motor industry.

    From motor classification and design of motor components to model setup and material and bearing selections, this comprehensive text covers the fundamentals of practical design and design-related issues, modeling and simulation, engineering analysis, manufacturing processes, testing procedures, and performance characteristics of electric motors today. This Second Edition adds three brand new chapters on motor breaks, motor sensors, and power transmission and gearing systems. Using a practical approach, with a focus on innovative design and applications, the book contains a thorough discussion of major components and subsystems, such as rotors, shafts, stators, and frames, alongside various cooling techniques, including natural and forced air, direct- and indirect-liquid, phase change, and other newly-emerged innovative cooling methods. It also analyzes the calculation of motor power losses, motor vibration, and acoustic noise issues, and presents engineering analysis methods and case-study results.

    While suitable for motor engineers, designers, manufacturers, and end users, the book will also be of interest to maintenance personnel, undergraduate and graduate students, and academic researchers.

    Preface (2nd edition) xxi Preface (1st edition) Author List of Symbols 1. Introduction to Electric Motors 1.1 History of Electric Machines 1.2 Motor Design Characteristics 1.2.1 Motor Torque 1.2.1 Static and Dynamic Torque 1.2.2 Motor Speed 1.2.3 Torque Density 1.2.4 Motor Power and Power Factor 1.2.5 Torque–Speed Characteristics 1.2.6 Mechanical Resonance and Resonant Frequency 1.2.7 Load-to-Motor Inertia Ratio 1.2.8 Duty Cycle 1.2.9 Motor Efficiency 1.2.10 Motor Insulation 1.2.11 Motor Operation Reliability 1.3 Classifications of Electric Motors 1.3.1 DC and AC Motors 1.3.2 Single-Phase and Three-Phase Motors 1.3.3 Induction and Permanent Magnet Motors 1.3.4 Synchronous and Asynchronous Motors 1.3.5 Servo and Stepper Motors 1.3.6 Gear Drive and Direct Drive Motors 1.3.7 Brush and Brushless Motors 1.3.8 Reluctance Motors 1.3.9 Radial flux and Axial flux Motors 1.3.10 Rotary and Linear Motors 1.3.11 Open and Enclosed Motors 1.3.12 Housed and Frameless Motors 1.3.13 Internal Rotor Motor and External Rotor Motor 1.3.14 Specialty Electric Motors 1.3.15 Motor Classification according to Power Rating 1.4 Motor Design and Operation Parameters 1.4.1 Back EMF Constant, Ke 1.4.2 Torque Constant, Kt 1.4.3 Velocity Constant, Kv 1.4.4 Motor Constant, Km 1.4.5 Mechanical Time Constant, τm 1.4.6 Electrical Time Constant, τe 1.4.7 Thermal Time Constant, τth 1.4.8 Viscous Damping, Kvd 1.5 Sizing Equations 1.6 Motor Design Process and Considerations 1.6.1 Design Process 1.6.2 Design Integration 1.6.3 Mechatronics 1.6.4 Temperature Effect on Motor Performance 1.7 Motor Failure Modes 1.8 IP Code References 2. Rotor Design 2.1 Rotor in Induction Motor 2.1.1 Wound Rotor 2.1.2 Squirrel Cage Rotor 2.1.3 Induction Motor Types and Their Performing Characteristics 2.2 Permanent Magnet Rotor 2.2.1 Discovery of Phenomenon of Magnetism 2.2.2 Permanent Magnet Characteristics 2.2.3 Permanent Magnet Materials 2.2.4 Magnetization 2.2.5 Factors Causing Demagnetization 2.2.6 Maximum Operating Temperature 2.2.7 Permanent Magnet Mounting and Retention Methods 2.2.8 Ring Magnets 2.2.9 Corrosion Protection of Permanent Magnets 2.3 Rotor Manufacturing Process 2.3.1 Lamination Materials 2.3.2 Lamination Cutting 2.3.3 Lamination Surface Insulation 2.3.4 Lamination Annealing 2.3.5 Lamination Stacking 2.3.6 Rotor Casting for Squirrel Cage Motor 2.3.7 Heat Treatment of Casted Rotor 2.3.8 Rotor Assembly 2.3.9 Rotor Machining and Runout Measurement 2.3.10 Rotor Balancing 2.4 Interference Fit 2.4.1 Press Fit 2.4.2 Shrink Fit 2.4.3 Serration Fit 2.4.4 Fitting with Adjustable Ringfeder® Locking Devices 2.4.5 Fitting with Tolerance Rings 2.5 Stress Analysis of Rotor 2.6 Rotordynamic Analysis 2.6.1 Rotor Inertia 2.6.2 Motor Critical Speed and Resonance 2.7 Rotor Burst Containment Analysis 2.7.1 Rotor Burst Speed 2.7.2 Energy in Rotating Rotor 2.7.3 Rotor Burst Containment Design References 3. Shaft Design 3.1 Shaft Materials 3.2 Shaft Loads 3.3 Solid and Hollow Shafts 3.4 Shaft Design Methods 3.4.1 Macaulay’s Method 3.4.2 Area-Moment Method 3.4.3 Castigliano’s Method 3.4.4 Graphical Method 3.5 Engineering Calculations 3.5.1 Normal Stress for Shaft Subject to Axial Force 3.5.2 Bending Stress for Shaft Subjected to Bending Moment 3.5.3 Torsional Shear Stress and Torsional Deflection 3.5.4 Lateral Deflection of Shaft 3.6 Shaft Design Issues 3.6.1 Shaft Design Considerations 3.6.2 Shaft Rigidity 3.6.3 Critical Shaft Speed 3.6.4 Dimensional Tolerance 3.6.5 Shaft Runout 3.6.6 Shaft Eccentricity 3.6.7 Heat Treatment and Shaft Hardness 3.6.8 Shaft Surface Finishing 3.6.9 Shaft Lead 3.6.10 Shaft Seal 3.6.11 Diametrical Fit Types 3.7 Stress Concentration 3.8  Torque Transmission through Mechanical Joints 3.8.1 Keyed Shafts 3.8.2 Spline Shafts 3.8.3 Tapered Shafts 3.9 Fatigue Failure under Alternative Loading 3.10 Shaft Manufacturing Methods 3.10.1 Machined Shaft 3.10.2 Forged Shaft 3.10.3 Welded Hollow Shaft 3.10.4 Shaft Measurement 3.11 Shaft Misalignment between Motor and Driven Machine 3.11.1 Type of Misalignment 3.11.2 Correction of Shaft Misalignment 3.12 Shaft Coupling 3.12.1 Rigid and Semirigid Couplings 3.12.2 Flexible Couplings 3.12.3 Noncontact Couplings 3.12.4 Oil Shear Couplings References 4. Stator Design 4.1 Stator Lamination 4.1.1 State Lamination Material 4.1.2 Stator Lamination Patterns 4.2 Magnet Wire 4.2.1 Regular Magnet Wire 4.2.2 Self-Adhesive Magnet Wire 4.2.3 Litz Wire 4.3 Stator Insulation 4.3.1 Injection Molded Plastic Insulation 4.3.2 Slot Liner 4.3.3 Glass Fiber-Reinforced Mica Tape 4.3.4 Powder Coating on Stator Core 4.4 Manufacturing Process of a Stator Core 4.4.1 Stator Lamination Cutting 4.4.2 Lamination Fabrication Process 4.4.3 Lamination Annealing 4.4.4 Lamination Stacking 4.4.5 Stator Winding 4.5 Stator Encapsulation and Impregnation 4.5.1 Encapsulation 4.5.2 Varnish Dipping 4.5.3 Trickle Impregnation 4.5.4 Vacuum Pressure Impregnation 4.6 Stator Design Considerations 4.6.1 Cogging Torque 4.6.2 Air Gap 4.6.3 Stator Cooling 4.6.4 Robust Design of Stator 4.6.5 Power Density Improvement 4.7 Mechanical Stress of Stator References 5. Motor Frame Design 5.1 Type of Motor Housing based on Manufacturing Method 5.1.1 Wrapped Housing 5.1.2 Casted Housing 5.1.3 Machined Housing 5.1.4 Stamped Housing 5.1.5 Extruded Aluminum Motor Housing 5.1.6 Motor Housing with Composite Materials 5.1.7 Motor Housing Fabricated by 3D Printing and Other Additive Manufacturing Processes 5.1.8 Frameless Motor 5.2 Testing Methods of Casted Motor Housing 5.3 Endbell Manufacturing 5.3.1 Casted Endbell 5.3.2 Stamped Endbell 5.3.3 Iron Casting versus Aluminum Casting 5.3.4 Machined Endbell 5.3.5 Forged Endbell 5.4 Motor Assembly Methods 5.4.1 Tie Bar 5.4.2 Tapping at Housing End Surface 5.4.3 Forged Z-Shaped Fastener 5.4.4 Rotary Fastener 5.4.5 Other Types of Fasteners 5.5 Fastening System Design 5.5.1 Types of Thread Fasteners 5.5.2 Thread Formation 5.5.3 Fastener Preload 5.5.4 Fastener-Tightening Process 5.5.5 Tightening Torque 5.5.6 Thread Engagement and Load Distribution 5.6 Common Types of Electric Motor Enclosures 5.6.1 Open Drip Proof Enclosure 5.6.2 Totally Enclosed Non-Ventilated Enclosure 5.6.3 Totally Enclosed Fan Cooled Enclosure 5.6.4 Totally Enclosed Air over Enclosure 5.6.5 Totally Enclosed Forced Ventilated Enclosure 5.6.6 Washdown Enclosure 5.6.7 Explosion Proof Enclosure 5.7 Anticorrosion of Electric Motor and Components 5.7.1 Surface Treatment Methods 5.7.2 Anticorrosion Treatment of Electric Motor 5.7.3 Hydrogen Embrittlement Issues References 6. Motor Bearing 6.1 Bearing Classification 6.1.1 Journal Bearing 6.1.2 Rolling Bearing 6.1.3 Noncontact Bearing 6.1.4 Sensor Bearing 6.1.5 Slewing Bearing 6.1.6 Cross-Roller Bearing 6.1.7 Ball Screw 6.2 Bearing Design 6.2.1 Bearing Materials 6.2.2 Bearing Internal Clearances 6.2.3 Allowable Bearing Speed 6.2.4 Bearing Fitness 6.2.5 Prevention of Bearing Axial Movement 6.2.6 Bearing Load 6.3 Bearing Fatigue Life 6.3.1 Calculation of Bearing Fatigue Life 6.3.2 Bearing Failure Probability Distribution 6.3.3 Influence of Unbalance on Bearing Fatigue Life 6.3.4 Influence of Wear on Bearing Fatigue Life 6.3.5 Influence of Internal Radial Clearance on Bearing Fatigue Life 6.4 Bearing Failure Mode 6.4.1 Major Causes of Premature Bearing Failure 6.4.2 Lubricant Selection 6.4.3 Improper Bearing Lubrication 6.4.4 Lubricant Contamination 6.4.5 Grease Leakage 6.4.6 Bearing Sealing and Bearing Shielding 6.4.7 Excessive Load 6.4.8 Internal Radial Interference Condition 6.4.9 Bearing Current 6.4.10 Impact of High Temperature on Bearing Failure 6.4.11 Bearing Failure Associated with Motor Vibration and Overloading 6.4.12 Improper Bearing Installation and Bearing Misalignment 6.4.13 Vertically Mounted Motor 6.5 Bearing Noise 6.6 Bearing Selection 6.6.1 Bearing Type Selection Based on Load 6.6.2 Bearing Type Selection Based on Speed 6.6.3 Selection of Bearing Size 6.7 Bearing Performance Improvement References 7. Motor Brake 7.1 Fundamental Knowledge of Motor Brake 7.1.1 Static and Dynamic Friction 7.1.2 Kinetic Energy of Rotating Object 7.1.3 Wear 7.1.4 Brake Frictional Materials 7.1.5 Brake Operation Mode 7.2 Key Design Parameters and Considerations in Brake Design 7.2.1 Brake Torque 7.2.2 Brake Operation Time 7.2.3 Braking Energy for Single Operation and Operation Frequency per Minute 7.2.4 Mean Dissipation Power 7.2.5 Temperature Rise and Thermal Capacity Rating 7.2.6 Factor of Safety 7.2.7 Brake Backlash 7.2.8 Brake Noise 7.2.9 Maximum Sliding Speed 7.2.10 Reliability and Durability 7.2.11 Brake Operation Cycle 7.2.12 Brake Mounting Arrangement 7.2.13 Brake Size 7.2.14 Brake Integration with Electric Motor 7.2.15 Brake Ingress Protection Rating 7.2.16 Accumulation of Brake Wear Particles 7.3 Classification of Braking System 7.3.1 Electromagnetic Brak 7.3.2 Mechanical Brake 7.3.3 Oil Shear Brake 7.3.4 Hydraulic Brake 7.4 Brake Failure 7.4.1 Overheating of Mating Friction Surfaces 7.4.2 Excessive Wear on Friction Surfaces 7.4.3 Failure due to Corrosion 7.4.4 Runout of Friction Disc 7.4.5 Thermomechanical Fatigue 7.5 Brake Design and Selection Considerations 7.5.1 Dynamic Stopping Brake or Holding Brake? 7.5.2 AC or DC Brake? 7.5.3 Braking Torque 7.5.4 Overall Inertia of System 7.5.5 Thermal Consideration in Brake Selection 7.5.6 Other Factors Affecting Brake Selection References 8. Servo Feedback Devices and Motor Sensors 8.1 Encoder 8.1.1 Resolution of Encoder 8.1.2 Type of Encoder 8.1.3 Absolute and Incremental Encoders 8.1.4 Rotary and Linear Encoder 8.1.5 Encoder Mounting 8.2 Resolver 8.2.1 Type of Resolver 8.2.2 Resolver Operating Parameters 8.2.3 Resolver Testing 8.3 Hall Effect Sensor 8.3.1 Linear Sensor 8.3.2 Threshold Sensor 8.4 Proximity Sensor 8.4.1 Inductive Proximity Sensor 8.4.2 Capacitive Proximity Sensor 8.4.3 Ultrasonic Proximity Sensor 8.4.4 Photoelectric Proximity Sensor 8.5 Other Motor Sensor 8.5.1 Force/Torque Sensor 8.5.2 Temperature Sensor 8.5.3 Vibration Sensor 8.5.4 Current Sensor 8.5.5 Pressure Sensor 8.5.6 Magnetic Field Sensor 8.6 Improving Motor Sensor Performance 8.6.1 Mitigation of Electrical Noise 8.6.2 Suppression of Temperature Rise 8.6.3 Utilization of Dual-Feedback Solution for Improving Motion Control Accuracy and Reliability 8.7 Development of Innovative Sensor 8.7.1 Sensor Miniaturization – Microsensor and Nanosensor 8.7.2 Advanced Wireless Sensor Technology 8.7.3 Smart Sensors 8.7.4 Color-Changing Dye Sensor for Detecting Motor Condition 8.7.5 Sensor with Newly Developed Material 8.8 Selection of Motor Feedback Devices and Sensors 8.9 Cable Technology References 9. Power Transmission and Gearing System 9.1 Characteristics of Gearing Systems 9.1.1 Gearing System Efficiency 9.1.2 Gear Ratio and Torque Ratio 9.1.3 Inertia Matching 9.1.4 Gear Tooth Profile 9.1.5 Backlash 9.1.6 Gear Stage 9.1.7 Gear Lubrication 9.1.8 Gear Contact Ratio 9.1.9 Temperature Rise and Thermal Effect on Gearing System Performance 9.1.10 Compact Structure 9.1.11 Acoustic Noise 9.1.12 Operation Reliability 9.2 Types of Modern Gearing Systems 9.2.1 Strain Wave Gearing System 9.2.2 Planetary Gearing System 9.2.3 Cycloidal Gearing System 9.2.4 Rotate Vector Gearing System 9.2.5 Magnetic Gearing System 9.2.6 Continuously Variable Strain Wave Transmission 9.2.7 Pulse Drive 9.2.8 Abacus Drive 9.2.9 Circular Wave Drive 9.2.10 Archimedes Drive 9.2.11 Spiral Cam Driven Block 9.2.12 Clutch-Type Stepless Speed Changer 9.3 Conventional Gearing Systems 9.3.1 Spur Gear 9.3.2 Helical Gear 9.3.3 Bevel Gear 9.3.4 Spiroid Gear 9.3.5 Helicon Gear 9.3.6 Worm Gear 9.3.7 Comparison of Conventional Gearing Systems 9.4 Gearhead and Gearmotor 9.4.1 Gearhead 9.4.2 Gearmotor 9.5 Failure of Gearing System 9.6 Selection of Gearing System References 10. Motor Power Losses 10.1 Power Losses in Windings due to Electric Resistance in Copper Wires 10.2 Eddy Current and Magnetic Hysteresis Losses 10.2.1 Eddy Current Loss 10.2.2 Magnetic Hysteresis Loss 10.2.3 Calculations of Eddy-Current and Magnetic Hysteresis Losses  10.2.4 Losses in Stator and Rotor Iron Cores 10.2.5 Losses in PMs 10.2.6 Power Losses in Other Core Components 10.3 Mechanical Friction Losses 10.3.1 Bearing Losses 10.3.2 Sealing Losses 10.3.3 Brush Losses 10.4 Windage Losses 10.4.1 Windage Loss due to Rotating Rotor 10.4.2 Windage Loss due to Entrance Effect of Axial Air-Gap Flow 10.4.3 Windage Loss due to Stator Surface Roughness 10.4.4 Energy Loss due to Fluid Viscosity 10.4.5 Fan Losses 10.4.6 Ventilating Path Losses 10.4.7 Methods for Reducing Windage Losses 10.5 Stray Load Losses 10.6 Influence of Power Rating on Motor Power Losses References 11. Motor Cooling 11.1 Introduction 11.1.1 Passive and Active Cooling Techniques 11.1.2 Heat Transfer Enhancement Techniques 11.2 Conductive Heat Transfer Techniques 11.2.1 Conductive Heat Flux and Energy Equations 11.2.2 Encapsulation and Impregnation of Electric Motor 11.2.3 Enhanced Heat Transfer Using High-Thermal-Conductivity Material 11.2.4 Using Self-Adhesive Magnet Wire for Fabricating Stator Winding 11.3 Natural Convection Cooling with Fins 11.3.1 Cooling Fin 11.3.2 Fin Optimization 11.3.3 Heatsinks Manufactured with Additive Manufacturing Process 11.3.4 Applications of Various Fins in Motor Cooling 11.3.5 Pin-Fin Heat Sink 11.3.6 Thermal Interface Materials 11.4 Forced Air Cooling Techniques 11.4.1 Thermophysical Properties of Air 11.4.2 Direct Forced Air Cooling Techniques 11.4.3 Indirect Forced Air Cooling Techniques 11.4.4 Fan and Blower 11.5 Liquid Cooling Techniques 11.5.1 Thermophysical Properties of Coolants 11.5.2 Direct Liquid Cooling Techniques 11.5.3 Liquid Immersion Cooling 11.5.4 Indirect Liquid Cooling Techniques 11.6 Phase-Change Cooling Techniques 11.6.1 Cooling with Heat Pipes 11.6.2 Cooling with Vapor Chambers 11.6.3 Evaporative Cooling 11.6.4 Mist Cooling 11.7 Radiative Heat Transfer 11.8 Other Advanced State-of-the-Art Cooling Methods 11.8.1 Micro Channel Cooling Systems 11.8.2 Metal Foams 11.8.3 Heat Transfer Enhancement with Nanotechnology References 12. Motor Vibration and Acoustic Noise 12.1 Vibration and Noise in Electric Motor 12.2 Fundamentals of Vibration 12.2.1 Simple Harmonic Oscillating System 12.2.2 Damped Harmonic Oscillating System 12.2.3 Forced Vibration with Damping 12.2.4 Forced Vibration due to Mass Unbalance 12.2.5 Vibration Induced by Support Excitation 12.2.6 Directional Vibration 12.3 Electromagnetic Vibrations 12.3.1 Unbalanced Forces/Torques Caused by Electric Supply 12.3.2 Broken Rotor Bar and Cracked End Ring 12.3.3 Unbalanced Magnetic Pull due to Asymmetric Air Gap 12.3.4 Nonuniform Air Gap due to Stator Slots 12.3.5 Mutual Action Forces between Currents of Stator and Rotor 12.3.6 Vibration due to Unbalanced Voltage Operation 12.4 Mechanical Vibrations 12.4.1 Misaligned Shaft and Distorted Coupling 12.4.2 Defective Bearing 12.4.3 Self-Excited Vibration 12.4.4 Torsional Vibration 12.5 Vibration Measurements 12.6 Vibration Control 12.6.1 Damping Materials 12.6.2 Vibration Isolation 12.6.3 Magnetorheological Damper 12.6.4 Tuned Mass Damper 12.6.5 Double Mounting Isolation System 12.6.6 Viscoelastic Bearing Support 12.6.7 Self-Locking Fasteners 12.6.8 Active Vibration Isolation and Damping 12.6.9 Measurements of Motor Vibration 12.7 Fundamentals of Acoustic Noise 12.7.1 Tonal Noise and Broadband Noise 12.7.2 Sound Pressure Level and Sound Power Level 12.7.3 Octave Frequency Bands 12.7.4 Three Sound Weighting Scales 12.7.5 Averaged Sound Pressure Level 12.7.6 Type of Noise 12.8 Noise Classification and Measurement for Rotating Electric Machines 12.8.1 Noise Types in Rotating Electric Machine 12.8.2 Acoustic Anechoic Chamber 12.8.3 Measurement of Motor Noise 12.8.4 Acoustic Noise Field Measurement 12.9 Motor Noise Abatement Techniques 12.9.1 Active Noise Reduction Techniques 12.9.2 Passive Noise Reduction Techniques 12.9.3 Innovative Noise Abatement Methods References 13. Motor Testing 13.1 Motor Testing Standards 13.2 Testing Equipment and Measuring Instruments 13.2.1 Dynamometer 13.2.2 Thermocouples and Other Temperature Measuring Devices 13.2.3 Control System 13.2.4 Data Acquisition System 13.2.5 Torque Transducer 13.2.6 Power Quality Analyzer 13.2.7 Power Supply 13.2.8 Motor Test Platform 13.3 Testing Load Level 13.4 Testing Methods 13.4.1 Mechanical Differential Testing Method 13.4.2 Back-to-Back Testing Method 13.4.3 Indirect Loading Testing Method 13.4.4 Forward Short-Circuit Testing Method 13.4.5 Variable Inertia Testing Method 13.5 Off-Line Motor Testing 13.5.1 Winding Electrical Resistance Testing 13.5.2 Megohm Testing 13.5.3 Polarization Index Testing 13.5.4 High-Potential Testing 13.5.5 Surge Testing 13.5.6 Step-Voltage Testing 13.5.7 Determination of Rotor’s Moment of Inertia 13.6 Online Motor Testing 13.6.1 Locked Rotor Testing 13.6.2 Motor Heat Run Testing 13.6.3 Motor Efficiency Testing 13.6.4 Impulse Testing 13.6.5 Cogging Torque Testing 13.6.6 Torque Ripple Measurement References 14. Modeling, Simulation, and Analysis of Electric Motors 14.1 Computational Fluid Dynamics and Numerical Heat Transfer 14.1.1 Strategies in Modeling and Performing CFD Analysis 14.1.2 Rotating Flow Modeling 14.1.3 Porous Media Modeling 14.1.4 Numerical Simulation of Motor Cooling 14.2 Thermal Simulation with Lumped-Circuit Modeling 14.3 Thermal Analysis Using Finite Element Method 14.4 Rotordynamic Analysis 14.4.1 Problem Description 14.4.2 Bearing Support’s Stiffness and Damping 14.4.3 Rotordynamic Modeling 14.4.4 Results of Rotordynamic Analysis 14.5 Static and Dynamic Stress/Strain Analysis 14.5.1 Static Analysis 14.5.2 Dynamic Analysis 14.5.3 Shock Load 14.6 Fatigue Analysis 14.7 Torsional Resonance Analysis 14.8 Motor Noise Prediction 14.9 Buckling Analysis 14.10 Thermally Induced Stress Analysis 14.11 Thermal Expansion and Contraction Analysis References 15. Innovative and Advanced Motor Design 15.1 High-Temperature Superconducting Motor 15.2 Radial flux Multirotor or Multistator Motor 15.2.1 Radial flux Multirotor Motor 15.2.2 Radial flux Multistator Motor 15.2.3 Radial flux Brushless Dual-Rotor Machine 15.2.4 Radial flux Double-Stator PM Machine 15.2.5 High-Torque PM Motor with 3D Circumferential Flux Design 15.2.6 Radial flux Dual-Rotor, Dual-Stator Motor 15.2.7 Radial flux Integrated Magnetic-Geared In-Wheel Motor 15.3 Axial flux Multirotor or Multistator Motor15.3.1 Single-Sided and Double-Sided Axial flux Motor15.3.2 Multistage Axial flux Motor 15.3.3 Yokeless and Segmented Armature Motor15.3.4 Energy Efficient Axial flux Yokeless Motor with Modular Stator15.3.5 Axial flux Motor with PCB Stator 15.4 Hybrid Motor15.4.1 Hybrid Excitation Synchronous Machine 15.4.2 Hybrid Hysteresis PM Synchronous Motor 15.4.3 Hybrid Motor Integrating RF Motor and AF Motor15.4.4 Hybrid-Field Flux-Controllable PM Motor15.4.5 Hybrid Linear Motor 15.5 Conical Rotor Motor 15.6 Transverse Flux Motor 15.7 Reconfigurable Permanent Magnet Motor 15.8 Variable Reluctance Motor 15.9 Permanent Magnet Memory Motor 15.9.1 Variable Flux PM Memory Motor 15.9.2 Pole-Changing PM Memory Motor 15.9.3 Doubly Salient Memory Motor 15.10 Adjustable and Controllable Axial Rotor/Stator Alignment Motor 15.11 Piezoelectric Motor 15.12 Advanced Electric Machines for Renewable Energy 15.13 Micromotor, Nanomotor, and Molecular Motor 15.13.1 Micromotor 15.13.2 Nanomotor 15.13.3 Molecular Motor References Index


    Wei Tong, Ph.D, PE is chief engineer at Kollmorgen Corporation, a subsidiary of Danaher Corporation, Radford, Virginia, USA. He is an internationally recognized expert on mechanical–electrical–thermal systems. A fellow of the American Society of Mechanical Engineers and a registered professional engineer in the state of Virginia, USA, Dr. Tong holds 28 US patents and 16 foreign patents. He presently serves as an associate editor of ASME Journal of Heat Transfer and International Journal of Rotating Machinery.