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Full Description
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.
Contents
Preface xix
Chapter 1 Rotating Machine Insulation Systems 1
1.1 Types of Rotating Machines 1
1.1.1 AC Motors 2
1.1.2 Synchronous Generators 4
1.1.3 Induction Generators 6
1.1.4 Permanent Magnet (PM) Synchronous Motors and Generators 7
1.1.5 Classification by Cooling 7
1.2 Winding Components 9
1.2.1 Stator Winding 9
1.2.2 Insulated Rotor Windings 10
1.2.3 Squirrel Cage Induction Motor Rotor Windings 11
1.3 Types of Stator Winding Construction 11
1.3.1 Random-Wound Stators 12
1.3.2 Form-Wound Stators—Coil Type 12
1.3.3 Form-Wound Stators—Roebel Bar Type 13
1.4 Form-Wound Stator Winding Insulation System Features 14
1.4.1 Strand Insulation 14
1.4.2 Turn Insulation 17
1.4.3 Groundwall Insulation 19
1.4.4 Groundwall Partial Discharge Suppression 21
1.4.5 Groundwall Stress Relief Coatings for Conventional Stators 24
1.4.6 Surface Stress Relief Coatings for Inverter-Fed Stators 27
1.4.7 Conductor Shields 29
1.4.8 Mechanical Support in the Slot 30
1.4.9 Mechanical Support in the End winding 32
1.4.10 Transposition Insulation 34
1.5 Random-Wound Stator Winding Insulation System Features 36
1.5.1 Partial Discharge Suppression in Inverter-Fed Random Windings 37
1.6 Rotor Winding Insulation System Components 38
1.6.1 Salient Pole Rotor 40
1.6.2 Round Rotors 41
1.6.3 Induction Machine Wound Rotors 43
References 45
Chapter 2 Evaluating Insulation Materials and Systems 47
2.1 Aging Stresses 49
2.1.1 Thermal Stress 49
2.1.2 Electrical Stress 50
2.1.3 Ambient Stress (Factors) 52
2.1.4 Mechanical Stress 53
2.1.5 Radiation Stress 54
2.1.6 Multiple Stresses 54
2.2 Principles of Accelerated Aging Tests 54
2.2.1 Candidate and Reference Materials/Systems 55
2.2.2 Statistical Variation 55
2.2.3 Failure Indicators 61
2.3 Thermal Endurance Tests 62
2.3.1 Basic Principles 62
2.3.2 Thermal Identification and Classification 63
2.3.3 Insulating Material Thermal Aging Test Standards 64
2.3.4 Insulation System Thermal Aging Test Standards 64
2.3.5 Future Trends 67
2.4 Electrical Endurance Tests 67
2.4.1 Proprietary Tests for Form-Wound Coils 68
2.4.2 Standardized AC Voltage Endurance Test Methods for Form-Wound Coils/Bars 69
2.4.3 Voltage Endurance Tests for Inverter-Fed Windings 70
2.5 Thermal Cycling Tests 71
2.5.1 IEEE Thermal Cycling Test 72
2.5.2 IEC Thermal Cycling Test 73
2.6 Nuclear Environmental Qualification Tests 74
2.6.1 Environmental Qualification (EQ) by Testing 75
2.6.2 Environmental Qualification by Analysis 76
2.6.3 Environmental Qualification by a Combination of Testing and Analysis 77
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
3.4.1 Polyesters 90
3.4.2 Epoxides (Epoxy Resins) 92
3.5 Mica 95
3.5.1 Mica Splittings 95
3.5.2 Mica Paper 96
3.5.3 Mica Backing Materials 98
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
3.10.1 Early Systems 103
3.10.2 Asphaltic Mica Systems 103
3.10.3 Individual Coil and Bar Thermoset Systems 104
3.10.4 Global VPI Systems 105
3.11 Wire Transposition Insulation 106
3.12 Methods of Taping Stator Groundwall Insulation 107
3.13 Insulating Liners, Separators, and Sleeving 109
3.13.1 Random-Wound Stators 109
3.13.2 Rotors 110
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
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
6.1.1 Magnetic Fields 143
6.1.2 Ferromagnetism 143
6.1.3 Magnetization Saturation Curve 144
6.1.4 Ferromagnetic Materials 144
6.1.5 Permeability 145
6.1.6 Hysteresis Loss 145
6.1.7 Eddy Current Loss 146
6.1.8 Other Factors Affecting Core Loss 146
6.1.9 Effect of Direction of the Grain 148
6.1.10 Effect of Temperature 148
6.1.11 Effect of Heat Treatment 148
6.1.12 Effect of Impurities and Alloying Elements 148
6.1.13 Silicon/Aluminum Steels 149
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
6.6.1 Stator Core Construction: General 152
6.6.2 Hydrogenerator and Large Motor Stator Core Assembly and Support 153
6.6.3 Turbogenerator Stator Core Assembly and Support 154
6.6.4 Smaller Motor and Generator Stator Cores 155
6.6.5 Rotor Core Construction 155
References 157
Chapter 7 General Principles of Winding Failure, Repair and Rewinding 159
7.1 Failure Processes 159
7.1.1 Relative Failure Rates of Components 161
7.1.2 Factors Affecting Failure Mechanism Predominance 162
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
8.1.1 General Process 171
8.1.2 Root Causes 174
8.1.3 Symptoms 175
8.1.4 Remedies 176
8.2 Thermal Cycling 176
8.2.1 General Process 177
8.2.2 Root Causes 180
8.2.3 Symptoms 180
8.2.4 Remedies 181
8.3 Inadequate Resin Impregnation or Dipping 181
8.3.1 General Process 182
8.3.2 Root Causes 183
8.3.3 Symptoms 184
8.3.4 Remedies 184
8.4 Loose Coils in the Slot 185
8.4.1 General Process 185
8.4.2 Root Causes 186
8.4.3 Symptoms 189
8.4.4 Remedies 190
8.5 Semiconductive Coating Failure 190
8.5.1 General Process 190
8.5.2 Root Causes 191
8.5.3 Symptoms 192
8.5.4 Remedies 193
8.6 Semiconductive/Grading Coating Overlap Failure 194
8.6.1 General Process 194
8.6.2 Root Causes 195
8.6.3 Symptoms 196
8.6.4 Remedies 196
8.7 High Intensity Slot Discharge 197
8.7.1 General Process 198
8.7.2 Root Causes 198
8.7.3 Symptoms 199
8.7.4 Repairs 199
8.8 Vibration Sparking (Spark Erosion) 199
8.8.1 General Process 199
8.8.2 Root Cause 201
8.8.3 Symptoms 201
8.8.4 Repair 202
8.9 Transient Voltage Surges 202
8.9.1 General Process 203
8.9.2 Root Causes 204
8.9.3 Symptoms 204
8.9.4 Remedies 206
8.10 Repetitive Voltage Surges Due to Drives 207
8.10.1 General Process 207
8.10.2 Root Cause 209
8.10.3 Symptoms 209
8.10.4 Remedies 210
8.11 Contamination (Electrical Tracking) 211
8.11.1 General Process 211
8.11.2 Root Causes 214
8.11.3 Symptoms 214
8.11.4 Remedies 214
8.12 Abrasive Particles 216
8.12.1 General Process 216
8.12.2 Root Causes 216
8.12.3 Symptoms and Remedies 216
8.13 Chemical Attack 217
8.13.1 General Process 217
8.13.2 Root Causes 218
8.13.3 Symptoms 218
8.13.4 Remedies 219
8.14 Inadequate End Winding Spacing 219
8.14.1 General Process 220
8.14.2 Root Causes 222
8.14.3 Symptoms 222
8.14.4 Remedies 222
8.15 End Winding Vibration 224
8.15.1 General Process 224
8.15.2 Root Causes 225
8.15.3 Symptoms 226
8.15.4 Remedies 227
8.16 Stator Coolant Water Leaks 228
8.16.1 General Process 228
8.16.2 Root Causes 229
8.16.3 Symptoms 230
8.16.4 Remedies 230
8.17 Poor Electrical Connections 231
8.17.1 General Process 231
8.17.2 Root Causes 232
8.17.3 Symptoms 232
8.17.4 Remedies 233
References 233
Chapter 9 Round Rotor Winding Failure Mechanisms and Repair 235
9.1 Thermal Deterioration 235
9.1.1 General Process 236
9.1.2 Root Cause 236
9.1.3 Symptoms 237
9.2 Thermal Cycling 237
9.2.1 General Process 238
9.2.2 Root Cause 238
9.2.3 Symptoms 240
9.3 Abrasion Due to Imbalance or Turning Gear Operation (Copper Dusting) 241
9.3.1 General Process 242
9.3.2 Root Causes 243
9.3.3 Symptoms 244
9.4 Pollution (Tracking) 244
9.4.1 General Process 244
9.4.2 Root Causes 245
9.4.3 Common Symptoms 245
9.5 Repetitive Voltage Surges 245
9.5.1 General Process 246
9.5.2 Root Causes 246
9.5.3 Common Symptoms 247
9.6 Centrifugal Force 247
9.6.1 General Process 247
9.6.2 Root Causes 247
9.6.3 Common Symptoms 248
9.7 Operating Without Field Current 249
9.7.1 Loss of Field During Operation 249
9.7.2 Inadvertent Closure of Generator Breaker 249
9.7.3 Root Causes 250
9.7.4 Common Symptoms 250
9.8 Remedies 250
References 252
Chapter 10 Salient Pole Rotor Winding Failure Mechanisms And Repair 253
10.1 Thermal Deterioration 253
10.1.1 General Process 253
10.1.2 Root Causes 254
10.1.3 Common Symptoms 254
10.2 Thermal Cycling 255
10.2.1 General Process 255
10.2.2 Root Causes 255
10.2.3 Common Symptoms 256
10.3 Pollution (Tracking and Moisture Absorption) 256
10.3.1 General Process 257
10.3.2 Root Causes 257
10.3.3 Common Symptoms 258
10.4 Abrasive Particles 258
10.4.1 General Process 258
10.4.2 Root Causes 258
10.4.3 Common Symptom 259
10.5 Centrifugal Force 259
10.5.1 General Process 259
10.5.2 Root Causes 259
10.5.3 Common Symptoms 259
10.6 Repetitive Voltage Surges 260
10.6.1 General Process 260
10.6.2 Root Causes 260
10.6.3 Common Symptoms 261
10.7 Salient Pole Repair 261
References 263
Chapter 11 Wound Rotor Winding Failure Mechanisms and Repair 265
11.1 Voltage Surges 266
11.1.1 General Process 266
11.1.2 Root Causes 267
11.1.3 Common Symptoms 267
11.2 Unbalanced Stator Voltages 267
11.2.1 General Process 267
11.2.2 Root Causes 268
11.2.3 Common Symptoms 268
11.3 High Resistance Connections-Bar Lap and Wave Windings 268
11.3.1 General Process 268
11.3.2 Root Causes 268
11.3.3 Common Symptoms 268
11.4 End Winding Banding Failures 269
11.4.1 General Process 269
11.4.2 Root Causes 269
11.4.3 Common Symptoms 269
11.5 Slip Ring Insulation Shorting and Grounding 270
11.5.1 General Process 270
11.5.2 Root Causes 270
11.6 Wound Rotor Winding Repair 271
11.6.1 Failed Windings 271
11.6.2 Contaminated Windings and Slip Ring Insulation 271
11.6.3 Failed Connections in Bar-Type Windings 271
11.6.4 Damaged End Winding Banding 271
11.6.5 Failed or Contaminated Slip Ring Insulation 272
References 272
Chapter 12 Squirrel Cage Induction Rotor Winding Failure Mechanisms and Repair 273
12.1 Thermal 273
12.1.1 General Process 274
12.1.2 Root Causes 274
12.1.3 Common Symptoms 275
12.2 Cyclic Mechanical Stressing 275
12.2.1 General Process 276
12.2.2 Root Causes 277
12.2.3 Common Symptoms 278
12.3 Poor Design/Manufacture 278
12.3.1 General Process and Root Causes 279
12.3.2 Common Symptoms 281
12.4 Repairs 283
References 284
Chapter 13 Core Lamination Insulation Failure and Repair 285
13.1 Thermal Deterioration 285
13.1.1 General Process 286
13.1.2 Root Causes 286
13.1.3 Common Symptoms 289
13.2 Electrical Degradation 290
13.2.1 General Process 290
13.2.2 Root Causes 291
13.2.3 Common Symptoms 294
13.3 Mechanical Degradation 295
13.3.1 General Process 295
13.3.2 Root Causes 296
13.3.3 Symptoms 301
13.4 Failures Due to Manufacturing Defects 303
13.4.1 General Process 303
13.4.2 Root Causes 304
13.4.3 Symptoms 304
13.5 Core Repairs 305
13.5.1 Loose Cores 305
13.5.2 Core Insulation Shorting 306
13.5.3 Core Damage Due to Winding Electrical Faults 307
13.5.4 False Tooth 308
13.5.5 Cracked Through-Bolt Insulation 308
13.5.6 Split Core Repairs 308
References 309
Chapter 14 General Principles of Testing and Monitoring 311
14.1 Purpose of Testing and Monitoring 311
14.1.1 Assessing Winding Condition and Remaining Winding Life 311
14.1.2 Prioritizing Maintenance 312
14.1.3 Commissioning and Warranty Testing 312
14.1.4 Determining Root Cause of Failure 313
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
15.1.1 Purpose and Theory 320
15.1.2 Test Method 322
15.1.3 Interpretation 324
References 385
Chapter 16 In-service Monitoring of Stator and Rotor Windings 389
16.1 Thermal Monitoring 390
16.1.1 Stator Winding Point Sensors 390
16.1.2 Rotor Winding Sensors 392
16.1.3 Data Acquisition and Interpretation 393
16.1.4 Thermography 394
References 435
Chapter 17 Core Testing 439
17.1 Knife 439
17.1.1 Purpose and Theory 439
17.1.2 Test Method 440
17.1.3 Interpretation 440
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
References 486
Chapter 19 Acceptance and Site Testing of New Windings 487
19.1 Stator Winding Insulation System Prequalification Tests 487
19.1.1 Dissipation Factor Tip-Up 488
19.1.2 Partial Discharge Test for Conventional Windings 488
19.1.3 Partial Discharge Test for Inverter Fed Windings 489
19.1.4 Impulse (Surge) 490
References 506
Chapter 20 Maintenance Strategies 509
20.1 Maintenance and Inspection Options 509
20.1.1 Breakdown or Corrective Maintenance 510
20.1.2 Time-Based or Preventative Maintenance 510
Reference 525
Appendix A Insulation Material Tables 527
Appendix B Insulation System Tables 553
Index 629
