A fully expanded new edition documenting the significant improvements that have been made to the tests and monitors of electrical insulation systems
Electrical Insulation for Rotating Machines: Design, Evaluation, Aging, Testing, and Repair, Second Edition covers all aspects in the design, deterioration, testing, and repair of the electrical insulation used in motors and generators of all ratings greater than fractional horsepower size. It discusses both rotor and stator windings; gives a historical overview of machine insulation design; and describes the materials and manufacturing methods of the rotor and stator winding insulation systems in current use (while covering systems made over fifty years ago). It covers how to select the insulation systems for use in new machines, and explains over thirty different rotor and stator winding failure processes, including the methods to repair, or least slow down, each process. Finally, it reviews the theoretical basis, practical application, and interpretation of forty different tests and monitors that are used to assess winding insulation condition, thereby helping machine users avoid unnecessary machine failures and reduce maintenance costs.
Electrical Insulation for Rotating Machines:
- Documents the large array of machine electrical failure mechanisms, repair methods, and test techniques that are currently available
- Educates owners of machines as well as repair shops on the different failure processes and shows them how to fix or otherwise ameliorate them
- Offers chapters on testing, monitoring, and maintenance strategies that assist in educating machine users and repair shops on the tests needed for specific situations and how to minimize motor and generator maintenance costs
- Captures the state of both the present and past “art” in rotating machine insulation system design and manufacture, which helps designers learn from the knowledge acquired by previous generations
An ideal read for researchers, developers, and manufacturers of electrical insulating materials for machines, Electrical Insulation for Rotating Machines will also benefit designers of motors and generators who must select and apply electrical insulation in machines.
Table of Contents
PREFACE xix
CHAPTER 1 ROTATING MACHINE INSULATION SYSTEMS 1
1.1 Types of Rotating Machines 1
1.2 Winding Components 9
1.3 Types of Stator Winding Construction 11
1.4 Form-Wound Stator Winding Insulation System Features 14
1.5 Random-Wound Stator Winding Insulation System Features 36
1.6 Rotor Winding Insulation System Components 38
References 45
CHAPTER 2 EVALUATING INSULATION MATERIALS AND SYSTEMS 47
2.1 Aging Stresses 49
2.2 Principles of Accelerated Aging Tests 54
2.3 Thermal Endurance Tests 62
2.4 Electrical Endurance Tests 67
2.5 Thermal Cycling Tests 71
2.6 Nuclear Environmental Qualification Tests 74
2.7 Multifactor Stress Testing 77
2.8 Material Property Tests 78
References 80
CHAPTER 3 HISTORICAL DEVELOPMENT OF INSULATION MATERIALS AND SYSTEMS 83
3.1 Natural Materials for Form-Wound Stator Coils 84
3.2 Early Synthetics for Form-Wound Stator Coils 86
3.3 Plastic Films and Non-Wovens 89
3.4 Liquid Synthetic Resins 90
3.5 Mica 95
3.6 Glass Fibers 99
3.7 Laminates 100
3.8 Evolution of Wire and Strand Insulations 101
3.9 Manufacture of Random-Wound Stator Coils 102
3.10 Manufacture of Form-Wound Coils and Bars 103
3.11 Wire Transposition Insulation 106
3.12 Methods of Taping Stator Groundwall Insulation 107
3.13 Insulating Liners, Separators, and Sleeving 109
References 110
CHAPTER 4 STATOR WINDING INSULATION SYSTEMS IN CURRENT USE 111
4.1 Consolidation of Major Manufacturers 114
4.2 Description of Major Trademarked Form-Wound Stator Insulation Systems 115
4.3 Recent Developments for Form-Wound Insulation Systems 123
4.4 Random-Wound Stator Insulation Systems 127
References 129
CHAPTER 5 ROTOR WINDING INSULATION SYSTEMS 133
5.1 Rotor Slot and Turn Insulation 134
5.2 Collector Insulation 136
5.3 End Winding Insulation and Blocking 136
5.4 Retaining Ring Insulation 137
5.5 Direct-Cooled Rotor Insulation 138
5.6 Wound Rotors 139
5.7 Superconducting Sychronous Rotors 140
References 141
CHAPTER 6 ROTOR AND STATOR LAMINATED CORES 143
6.1 Magnetic Materials 143
6.2 Mill-Applied Insulation 149
6.3 Lamination Punching and Laser Cutting 150
6.4 Annealing and Burr Removal 151
6.5 Enameling or Film Coatings 151
6.6 Stator and Rotor Core Construction 152
References 157
CHAPTER 7 GENERAL PRINCIPLES OF WINDING FAILURE, REPAIR AND REWINDING 159
7.1 Failure Processes 159
7.2 Factors Affecting Repair Decisions 164
7.3 Rapid Repair of Localized Stator Winding Damage 165
7.4 Cutting out Stator Coils After Failure 166
7.5 Bar/Coil Replacement and Half Coil Splice 167
7.6 Rewinding 168
References 169
CHAPTER 8 STATOR FAILURE MECHANISMS AND REPAIR 171
8.1 Thermal Deterioration 171
8.2 Thermal Cycling 176
8.3 Inadequate Resin Impregnation or Dipping 181
8.4 Loose Coils in the Slot 185
8.5 Semiconductive Coating Failure 190
8.6 Semiconductive/Grading Coating Overlap Failure 194
8.7 High Intensity Slot Discharge 197
8.8 Vibration Sparking (Spark Erosion) 199
8.9 Transient Voltage Surges 202
8.10 Repetitive Voltage Surges Due to Drives 207
8.11 Contamination (Electrical Tracking) 211
8.12 Abrasive Particles 216
8.13 Chemical Attack 217
8.14 Inadequate End Winding Spacing 219
8.15 End Winding Vibration 224
8.16 Stator Coolant Water Leaks 228
8.17 Poor Electrical Connections 231
References 233
CHAPTER 9 ROUND ROTOR WINDING FAILURE MECHANISMS AND REPAIR 235
9.1 Thermal Deterioration 235
9.2 Thermal Cycling 237
9.3 Abrasion Due to Imbalance or Turning Gear Operation (Copper Dusting) 241
9.4 Pollution (Tracking) 244
9.5 Repetitive Voltage Surges 245
9.6 Centrifugal Force 247
9.7 Operating Without Field Current 249
9.8 Remedies 250
References 252
CHAPTER 10 SALIENT POLE ROTOR WINDING FAILURE MECHANISMS AND REPAIR 253
10.1 Thermal Deterioration 253
10.2 Thermal Cycling 255
10.3 Pollution (Tracking and Moisture Absorption) 256
10.4 Abrasive Particles 258
10.5 Centrifugal Force 259
10.6 Repetitive Voltage Surges 260
10.7 Salient Pole Repair 261
References 263
CHAPTER 11 WOUND ROTOR WINDING FAILURE MECHANISMS AND REPAIR 265
11.1 Voltage Surges 266
11.2 Unbalanced Stator Voltages 267
11.3 High Resistance Connections-Bar Lap and Wave Windings 268
11.4 End Winding Banding Failures 269
11.5 Slip Ring Insulation Shorting and Grounding 270
11.6 Wound Rotor Winding Repair 271
References 272
CHAPTER 12 SQUIRREL CAGE INDUCTION ROTOR WINDING FAILURE MECHANISMS AND REPAIR 273
12.1 Thermal 273
12.2 Cyclic Mechanical Stressing 275
12.3 Poor Design/Manufacture 278
12.4 Repairs 283
References 284
CHAPTER 13 CORE LAMINATION INSULATION FAILURE AND REPAIR 285
13.1 Thermal Deterioration 285
13.2 Electrical Degradation 290
13.3 Mechanical Degradation 295
13.4 Failures Due to Manufacturing Defects 303
13.5 Core Repairs 305
References 309
CHAPTER 14 GENERAL PRINCIPLES OF TESTING AND MONITORING 311
14.1 Purpose of Testing and Monitoring 311
14.2 Off-Line Testing Versus On-Line Monitoring 313
14.3 Role of Visual Inspections 314
14.4 Expert Systems to Convert Data Into Information 315
References 316
CHAPTER 15 OFF-LINE ROTOR AND STATOR WINDING TESTS 317
15.1 Insulation Resistance and Polarization Index 317
15.2 DC Hipot Test 326
15.3 Polarization/Depolarization Current (PDC) 330
15.4 DC Conductivity 331
15.5 Poor Connection Hot Spot (High Current-Infrared Camera) 334
15.6 AC Hipot 335
15.7 Capacitance 339
15.8 Stator Capacitance Tip-Up 342
15.9 Capacitive Impedance Test for Motor Stators 344
15.10 Dissipation (or Power) Factor 344
15.11 Power (Dissipation) Factor Tip-Up 348
15.12 Off-Line Partial Discharge for Conventional Windings 350
15.13 Off-Line Partial Discharge for Inverter-Fed Windings 357
15.14 Stator Blackout and Ultraviolet Imaging 359
15.15 Stator Partial Discharge Probe 361
15.16 Stator Surge Voltage 363
15.17 Inductive Impedance 367
15.18 Semiconductive Coating Contact Resistance 368
15.19 Conductor Coolant Tube Resistance 369
15.20 Stator Wedge Tap 370
15.21 Slot Side Clearance 373
15.22 Stator Slot Radial Clearance 374
15.23 Stator End Winding Bump 375
15.24 Stator Pressure and Vacuum Decay 377
15.25 Rotor Pole Drop (Voltage Drop) 378
15.26 Rotor RSO and Surge 380
15.27 Rotor Growler 382
15.28 Rotor Fluorescent Dye Penetrant 383
15.29 Rotor Rated Flux 384
15.30 Rotor Single-Phase Rotation 385
References 385
CHAPTER 16 IN-SERVICE MONITORING OF STATOR AND ROTOR WINDINGS 389
16.1 Thermal Monitoring 390
16.2 Condition Monitors and Tagging Compounds 395
16.3 Ozone 398
16.4 Online Partial Discharge Monitor 400
16.5 Online Capacitance and Dissipation Factor 415
16.6 Endwinding Vibration Monitor 417
16.7 Synchronous Rotor Flux Monitor 420
16.8 Current Signature Analysis 427
16.9 Bearing Vibration Monitor 432
16.10 Stator Winding Water Leak Monitoring 435
References 435
CHAPTER 17 CORE TESTING 439
17.1 Knife 439
17.2 Rated Flux 441
17.3 Core Loss 450
17.4 Low Core Flux (El-CID) 451
References 461
CHAPTER 18 NEW MACHINE WINDING AND REWIND SPECIFICATIONS 463
18.1 Objective of Stator and Rotor Winding Specifications 464
18.2 Trade-Offs Between Detailed and General Specifications 464
18.3 General Items for Specifications 465
18.4 Technical Requirements for New Stator Windings 467
18.5 Technical Requirements for Insulated Rotor Windings 475
References 486
CHAPTER 19 ACCEPTANCE AND SITE TESTING OF NEW WINDINGS 487
19.1 Stator Winding Insulation System Prequalification Tests 487
19.2 Stator Winding Insulation System Factory and On-Site Tests 494
19.3 Factory and On-Site Tests for Rotor Windings 501
19.4 Core Insulation Factory and On-Site Tests 505
References 506
CHAPTER 20 MAINTENANCE STRATEGIES 509
20.1 Maintenance and Inspection Options 509
20.2 Maintenance Strategies for Various Machine Types and Applications 515
Reference 525
APPENDIX A INSULATION MATERIAL TABLES 527
APPENDIX B INSULATION SYSTEM TABLES 553
INDEX 629
