Mechanical Design and Manufacturing of Electric Motors

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, tm 1.4.6 Electrical Time Constant, te 1.4.7 Thermal Time Constant, tth 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.

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.