Electrical Insulation for Rotating Machines: Design, Evaluation, Aging, Testing, and Repair

381 Pages·2004·2.73 MB·English

by  Greg C. Stone

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ELECTRICAL INSULATION
FOR ROTATING MACHINES
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IEEE Press
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Stamatios V. Kartalopoulos, Editor in Chief
M. Akay R. J. Herrick M. Padgett
R. J. Baker D. Kirk W. D. Reeve
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Kenneth Moore, Director of Business and Information Services
Catherine Faduska, Senior Acquisitions Editor
Anthony VenGraitis, Project Editor
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Principles of Electric Machines with Power Electronic Applications,
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ELECTRICAL INSULATION
FOR ROTATING MACHINES
Design, Evaluation, Aging,
Testing, and Repair
GREG C. STONE
EDWARD A. BOULTER
IAN CULBERT
HUSSEIN DHIRANI
IEEE Press Series on Power Engineering
Mohamed E. El-Hawary, Series Editor
IEEE PRESS
A JOHN WILEY & SONS, INC., PUBLICATION
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Copyright © 2004 by the Institute of Electrical and Electronics Engineers, Inc. All rights reserved.
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Printed in the United States of America.
10 9 8 7 6 5 4 3 2 1
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CONTENTS
Preface xvii
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 Classification by Cooling 6
1.2 Purpose of Windings 7
1.2.1 Stator Winding 7
1.2.2 Insulated Rotor Windings 9
1.2.3 Squirrel Cage Induction Motor Rotor Windings 9
1.3 Types of Stator Winding Construction 9
1.3.1 Random-Wound Stators 10
1.3.2 Form-Wound Stators—Coil Type 10
1.3.3 Form-Wound Stators—Roebel Bar Type 12
1.4 Stator Winding Insulation System Features 12
1.4.1 Strand Insulation 12
1.4.2 Turn Insulation 17
1.4.3 Groundwall Insulation 18
1.4.4 Groundwall Partial Discharge Suppression 20
1.4.5 Groundwall Stress Relief Coatings 24
1.4.6 Mechanical Support in the Slot 27
1.4.7 Mechanical Support in the End-Winding 29
1.4.8 Transposition Insulation 31
1.5 Rotor Winding Insulation System Components 34
1.5.1 Salient Pole Rotor 35
1.5.2 Round Rotors 36
1.5.3 Induction Motor Wound Rotors 38
References 40
2 Evaluating Insulation Materials and Systems 43
2.1 Aging Stresses 44
2.1.1 Thermal Stress 45
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2.1.2 Electric Stress 46
2.1.3 Ambient Stress (Factors) 47
2.1.4 Mechanical Stress 48
2.1.5 Multiple Stresses 49
2.2 Principles of Accelerated Aging Tests 49
2.2.1 Candidate and Reference Materials/Systems 50
2.2.2 Statistical Variation 50
2.2.3 Failure Indicators 55
2.3 Thermal Endurance Tests 56
2.3.1 Basic Principles 56
2.3.2 Thermal Identification and Classification 57
2.3.3 Insulating Material Thermal Aging Tests 58
2.3.4 Insulation Systems Thermal Aging Tests 58
2.3.5 Future Trends 60
2.4 Electrical Endurance Tests 60
2.4.1 Proprietary Tests for Form-Wound Coils 61
2.4.2 Standardized Test Methods for Form-Wound Coils 62
2.5 Thermal Cycling Tests 63
2.5.1 IEEE Thermal Cycling Test 63
2.5.2 IEC Thermal Cycling Test 64
2.6 Multifactor Stress Testing 65
2.7 Nuclear Environmental Qualification Tests 65
2.7.1 Environmental Qualification (EQ) by Testing 66
2.7.2 Environmental Qualification by Analysis 66
2.7.3 Environmental Qualification by a Combination 67
of Testing and Analysis
2.8 Material Property Tests 67
References 69
3 Historical Development of Insulation Materials and Systems 73
3.1 Natural Materials 74
3.2 Early Synthetics 76
3.3 Plastic Films and Nonwovens 78
3.4 Liquid Synthetic Resins 79
3.4.1 Polyesters 79
3.4.2 Epoxides (Epoxy Resins) 81
3.5 Mica 83
3.5.1 Mica Splittings 83
3.5.2 Mica Paper 84
3.6 Glass Fibers 86
3.7 Laminates 87
3.8 Evolution of Wire and Strand Insulation 88
3.9 Manufacture of Random-Wound Stator Coils 89
3.10 Manufacture of Form-Wound Coils and Bars 89
3.10.1 Early Systems 89
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3.10.2 Asphaltic Mica Systems 90
3.10.3 Individual Coil and Bar Thermoset Systems 90
3.10.4 Global VPI Systems 91
3.11 Wire Transposition Insulation 92
3.12 Insulating Liners, Separators and Sleeving 93
3.12.1 Random-Wound Stators 93
3.12.2 Rotors 93
References 94
4 Stator Winding Insulation Systems in Current Use 95
4.1 Methods of Applying Form-Wound Stator Coil Insulation 97
4.2 Description of Major Trademarked Form-Wound Stator 99
Insulation Systems
4.2.1 Westinghouse Electric Co.:ThermalasticTM 99
4.2.2 General Electric Co.: Micapals I and IITM 100
Epoxy Mica MatTM, Micapal HTTM, and HydromatTM
4.2.3 Alsthom, GEC Alsthom, Alstom Power: Isotenax,TM 101
Resitherm,TMResiflex,TMResivacTM,and DuritenaxTM
4.2.4 Siemens AG, KWU: MicalasticTM 102
4.2.5 ABB Industrie AG: MicadurTM, Micadur Compact,TM 102
Micapact,TMMicarexTM
4.2.6 Toshiba Corporation: Tosrich,TMTostight ITM 103
4.2.7 Mitsubishi Electric Corporation 104
4.2.8 Hitachi Ltd.: HiResin,TMHi-Mold,TMSuper Hi-ResinTM 104
4.2.9 Summary of Present-Day Insulation Systems 104
4.3 Recent Developments for Form-Wound Insulation Systems 105
4.4 Random-Wound Stator Insulation Systems 107
4.4.1 Magnet Wire Insulation 107
4.4.2 Phase and Ground Insulation 108
4.4.3 Varnish Treatment and Impregnation 108
4.5 Revolutionary Stator Winding Insulation Systems 108
4.5.1 Superconducting Windings 108
4.5.2 PowerFormer™ 109
References 110
5 Rotor Winding Insulation Systems 113
5.1 Rotor Slot and Turn Insulation 114
5.2 Collector Insulation 115
5.3 End-Winding Insulation and Blocking 116
5.4 Retaining Ring Insulation 116
5.5 Direct-Cooled Rotor Insulation 117
6 Core Laminations and Their Insulation 119
6.1 Electromagnetic Materials 119
6.1.1 Magnetic Fields 119
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6.1.2 Ferromagnetism 119
6.1.3 Magnetization Saturation Curve 120
6.1.4 Ferromagnetic Materials 120
6.1.5 Permeability 121
6.1.6 Hysteresis Loop 121
6.1.7 Eddy Current Loss 122
6.1.8 Other Factors Affecting Core Loss 122
6.1.9 Effect of Direction of the Grain 124
6.1.10 Effect of Temperature 124
6.1.11 Effect of Heat Treatment 124
6.1.12 Effect of Impurities and Alloying Elements 124
6.1.13 Silicon/Aluminum Steels 125
6.2 Mill-Applied Insulation 125
6.3 Lamination Punching and Laser Cutting 125
6.4 Annealing and Burr Removal 126
6.5 Enameling or Film Coatings 127
References 127
7 General Principles of Winding Failure, Repair and Rewinding 129
7.1 Failure Processes 129
7.1.1 Relative Failure Rates of Components 131
7.1.2 Factors Affecting Failure Mechanism Predominance 132
7.2 Factors Affecting Repair Decisions 133
7.3 Cutting Out Stator Coils After Failure 134
7.4 Rewinding 134
References 135
8 Stator Failure Mechanisms and Repair 137
8.1 Thermal Deterioration 137
8.1.1 General Process 137
8.1.2 Root Causes 139
8.1.3 Symptoms 140
8.1.4 Remedies 141
8.2 Thermal Cycling 141
8.2.1 General Process 142
8.2.2 Root Causes 144
8.2.3 Symptoms 145
8.2.4 Remedies 145
8.3 Inadequate Impregnation or Dipping 146
8.3.1 General Process 146
8.3.2 Root Causes 146
8.3.3 Symptoms 148
8.3.4 Remedies 148
8.4 Loose Coils in the Slot 148
8.4.1 General Process 148
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8.4.2 Root Causes 149
8.4.3 Symptoms 151
8.4.4 Remedies 152
8.5 Semiconductive Coating Failure 152
8.5.1 General Process 152
8.5.2 Root Causes 153
8.5.3 Symptoms 153
8.5.4 Remedies 154
8.6 Semiconductive/Grading Coating Overlap Failure 155
8.6.1 General Process 155
8.6.2 Root Causes 156
8.6.3 Symptoms 156
8.6.4 Remedies 156
8.7 Repetitive Voltage Surges 157
8.7.1 General Process 158
8.7.2 Root Cause 159
8.7.3 Symptoms 160
8.7.4 Remedies 160
8.8 Contamination (Electrical Tracking) 161
8.8.1 General Process 161
8.8.2 Root Causes 164
8.8.3 Symptoms 164
8.8.4 Remedies 164
8.9 Abrasive Particles 165
8.9.1 General Process 165
8.9.2 Root Causes 165
8.9.3 Symptoms and Remedies 166
8.10 Chemical Attack 166
8.10.1 General Process 166
8.10.2 Root Causes 167
8.10.3 Symptoms 167
8.10.4 Remedies 167
8.11 Inadequate End-Winding Spacing 168
8.11.1 General Process 168
8.11.2 Root Causes 170
8.11.3 Symptoms 170
8.11.4 Remedies 171
8.12 End-Winding Vibration 172
8.12.1 General Process 172
8.12.2 Root Causes 173
8.12.3 Symptoms 174
8.12.4 Remedies 174
8.13 Stator Coolant Water Leaks 175
8.13.1 General Process 175
8.13.2 Root Causes 176
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8.13.3 Symptoms 177
8.13.4 Remedies 177
8.14 Poor Electrical Connections 177
8.14.1 General Process 178
8.14.2 Root Causes 178
8.14.3 Symptoms 178
8.14.4 Remedies 179
References 179
9 Rotor Winding Failure Mechanisms and Repair 181
9.1 Round Rotor Windings 181
9.1.1 Thermal Deterioration 181
9.1.2 Thermal Cycling 183
9.1.3 Abrasion Due To Imbalance or Turning Gear Operation 186
9.1.4 Pollution (Tracking) 187
9.1.5 Repetitive Voltage Surges 188
9.1.6 Centrifugal Force 189
9.1.7 Remedies 191
9.2 Salient Pole Rotor Windings 192
9.2.1 Thermal Aging 192
9.2.2 Thermal Cycling 193
9.2.3 Pollution (Tracking and Moisture Absorption) 194
9.2.4 Abrasive Particles 195
9.2.5 Centrifugal Force 195
9.2.6 Repetitive Voltage Surges 196
9.2.7 Remedies 196
9.3 Wound Induction Rotor Windings 198
9.3.1 Transient Overvoltages 198
9.3.2 Unbalanced Stator Voltages 199
9.3.3 High-Resistance Connections—Bar Lap 199
and Wave Windings
9.3.4 End-Winding Banding Failures 200
9.3.5 Slip Ring Insulation Shorting and Grounding 200
9.3.6 Remedies 201
9.4 Squirrel Cage Induction Rotor Windings 202
9.4.1 Thermal 202
9.4.2 Cyclic Mechanical Stressing 203
9.4.3 Poor Design/Manufacture 206
9.4.4 Repairs 208
References 209
10 Core Lamination Insulation Failure and Repair 211
10.1 Thermal Deterioration 211
10.1.1 General Process 212
10.1.2 Root Causes 212