Electrical Insulation for Rotating Machines

390 Pages·2006·5.3 MB·English

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ELECTRICAL INSULATION
FOR ROTATING MACHINES
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IEEE Press
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Piscataway, NJ 08854
IEEE Press Editorial Board
Stamatios V. Kartalopoulos, Editor in Chief
M. Akay R. J. Herrick M. Padgett
R. J. Baker D. Kirk W. D. Reeve
J. E. Brewer R. Leonardi S. Tewksbury
M. E. El-Hawary M. S. Newman G. Zobrist
Kenneth Moore, Director of Business and Information Services
Catherine Faduska, Senior Acquisitions Editor
Anthony VenGraitis, Project Editor
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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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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
TM
4.2.1 Westinghouse Electric Co.:Thermalastic 99
TM
4.2.2 General Electric Co.: Micapals I and II 100
TM TM TM
Epoxy Mica Mat , Micapal HT , and Hydromat
TM
4.2.3 Alsthom, GEC Alsthom, Alstom Power: Isotenax, 101
TM TM TM, TM
Resitherm, Resiflex, Resivac and Duritenax
TM
4.2.4 Siemens AG, KWU: Micalastic 102
TM TM
4.2.5 ABB Industrie AG: Micadur , Micadur Compact, 102
TM TM
Micapact, Micarex
TM TM
4.2.6 Toshiba Corporation: Tosrich, Tostight I 103
4.2.7 Mitsubishi Electric Corporation 104
TM TM TM
4.2.8 Hitachi Ltd.: HiResin, Hi-Mold, Super Hi-Resin 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