Electrical Motor Diagnostics / Edition 2

by Howard Penrose

Overview

Developed for electricians, mechanics, students, academia, and reliability/maintenance managers, Electrical Motor Diagnostics provides the information, case studies, and materials necessary to interpret motor circuit analysis, motor current signature analysis, electrical signature analysis, and other standard testing technologies for AC/DC electric motors, transformers, machine tool motors, synchronous motors, and generators including pass/fail values. Information on the development of a motor management program and the SUCCESS by DESIGN Time to Failure Estimation methodology for any technology are covered in detail.

Product Details

ISBN-13:	9780971245075
Publisher:	Success By Design
Publication date:	05/14/2008
Pages:	363
Product dimensions:	6.10(w) x 9.10(h) x 0.80(d)

About the Author

Dr. Penrose is the President of SUCCESS by DESIGN, a reliability and maintenance services consult and publisher whose clients include General Motors, UAW-GM, US Steel, Monsanto, and numerous other businesses, large and small, worldwide. He has 25 years in the reliability and maintenance industry with experience from the shop floor to academia and manufacturing to military. Dr Penrose was an adjunct professor of engineering at the University of Illinois at Chicago from 1997-1999 and a Senior Research Engineer at the UIC Energy Resources Center. He is well published in trade magazines, is frequently invited to speak at industrial reliability events.

Table of Contents

Table of Figures     xiii
Table of Tables     xix
Table of Equations     xxiii
Introduction     xxvii
The Motor Diagnostics and Motor Health Study     1
Electric Motor Repair Study, 1995     2
In Service Motor Testing, 1999     4
Success by Design Best Practice Survey     6
Dealing with the State of the Motor Testing Industry     7
Basic Electricity and Electro-Magnetism     9
Current, Voltage and Resistance     10
Electro-Magnetic Fields     11
Alternating Current Electricity (Hz)     12
Chapter 2 Questions     15
Electric Motor Theory     17
AC Induction Motor Theory     17
Wound Rotor Motors     24
Synchronous Motors     25
Direct Current Electric Motors     25
Machine Tool Motors     28
Traction Motors     29
Transformers     29
Chapter 3 Questions     35
Electrical Insulation Systems and Theory     37
The Motor Circuit     37
Insulation and Magnetic Field Effects     39
Winding Faults     45
Traditional Test Methods     45
Insulation to Ground Testing (Meg-Ohm Meters)     46
Polarization Index     46
Resistance Testing     46
Surge Comparison Testing     46
Modern Low-Voltage Testing: Motor Circuit Analysis     47
Detection of Winding Contamination     48
Overheated Windings     48
Winding Shorts     49
Additional Tests     49
Rotor Testing and Back Iron Effects on MCA     50
Armature and Commutator Contamination Detection     51
Summary of MCA Theory     52
Development of Experiments     52
Test Tolerances     54
MCA Tolerances     54
Surge Testing Tolerances     55
Experiment Test Results     55
Experiment 1     55
Experiment 2a     58
Experiment 2b     59
Experiment 2c     60
Experiment 3     62
Experiment Conclusions     64
Experiment 1 Conclusions     65
Experiment 2a Conclusions     65
Experiment 2b Conclusions     65
Experiment 2c Conclusions     65
Experiment 3 Conclusions     66
Summary      66
Chapter 4 Questions     67
Common Electric Motor Testing     69
Electrical Motor Diagnostics Defined     69
Condition-Based Technologies     70
Voltmeter Troubleshooting of an AC Motor     73
The Power of a Volt Meter     74
Checking Contacts with a Volt Meter     76
Checking Fuses with a Volt Meter     77
Ammeter Testing of an AC Motor     77
Analog Ammeters     77
Digital Ammeters     78
Load Measurements     78
Current Unbalance Conditions     79
Other Current Conditions     80
DC Resistance Testing of AC Machines     81
Selecting the Right Measurement Tool     81
Considerations When Using an Ohm Meter     85
Troubleshooting Motors with Ohm Meters     87
Classical Insulation Resistance Testing     87
The Basic Insulation Resistance Test     88
Utilizing Hi-Pot Testing for Insulation to Ground Stress Testing     94
Evaluating Motor Condition with Low Voltage Advanced Diagnostics     95
Motor Circuit Analysis     95
Surge Comparison Testing     102
Comparison of the 'Big Three'     104
Introduction to Electrical Signature Analysis     105
Multi-Technology Approach to CBM     111
Major Components and Failure Modes     113
Common Approaches to Multi-Technology     117
Application Opportunities     118
Chapter 5 Questions     121
Time to Failure Estimation     123
The Tools for TTFE     123
The Severity Modifier     125
Understanding Series and Parallel Availability     125
Time to Failure Estimation with MCA     129
Electric Motor Winding Failure     129
Insulation Breakdown     130
Stages of Winding Failure     131
Introduction to Motor Circuit Analysis (MCA)     134
Trending Fault Descriptions     134
AC Rotating Machine Testing     136
Time to Failure Estimation     136
Nuisance Tripping Situations     137
Winding Contamination     138
Winding Shorts     139
Test Cases     141
Chapter 6 Questions     143
Motor Circuit Analysis Testing AC Machines     145
Fault Detected Procedure     146
Data Collection and Test Result Issues     146
Rotor Test Procedure      149
Synchronous Machine Testing with MCA     150
Most Common Synchronous Motor Faults     152
Basic Steps for the Analysis of Synchronous Machines with MCA     152
Generator Analysis with MCA     153
Evaluating Generators with MCA     155
MCA Instrumentation: The ALL-TEST PRO 31     156
Analysis of Pin-Hole Shorts (VFD-Related Motor Failure)     157
AC Machine Case Studies     159
New Motor Phase Unbalance     159
Casting Void 200 HP Motor     163
ID Fan Motor Rebuild Defect     164
Cable Faults     165
Evaluation of an 8000 HP Synchronous Motor     167
AC Traction Motor - Good     168
Spindle Motor - Good     169
Brushless DC Servo - Coil-to-Coil Short     169
100 Horsepower, 1800 RPM with Dirty Windings     170
Servo Motor - Turn-to-Turn Fault     171
Rotor Position Related Unbalance     171
Motor Tested from MCC - Shorted Windings     172
Brand New 300 Horsepower Motor with Shorted Phase     173
3000 Horsepower with Fractured Rotor Bar     174
New 50 Horsepower, 2-pole Motor Combined Faults     175
300 HP, 2300 Volt, 3600 RPM Broken Rotor Bars      176
1000 HP, 3600 RPM - Special Signature on Good Motor     177
700 HP, 3600 RPM, Broken Rotor Bars and Cracked Shaft     178
Chapter 7 Questions     179
Motor Circuit Analysis Testing DC Motors     181
The Commutator     181
Brush and Commutator Operation     182
Seating, Tensioning and Cleaning     184
Basics of DC Machines for MCA Testing     186
Common DC Motor Electrical Faults     187
Armature Testing     188
Series Motor Testing     189
Shunt Motor Testing     190
Compound Motor Testing     190
General DC MCA Testing Notes     191
Chapter 8 Questions     193
Electrical Signature Analysis Theory     195
Alternating Current Induction Motors     197
Induction Motor Troubleshooting Procedure     197
Induction Motor Troubleshooting Analysis Overview     198
Power Quality and Electrical Analysis     199
Rotor Analysis     201
AC Motor and Stator Analysis     204
Driven Equipment Evaluation     206
Belts     206
Gear Mesh     207
Driven Equipment - Blade Pass Frequencies      207
Generator Analysis with ESA     208
DC Electric Motors     208
DC Motor Testing Procedure     209
Basic DC Motor Analysis     210
Chapter 9 Questions     212
Electrical Signature Analysis Pattern Recognition AC Machines     213
The Elusive Stator Slots and Rotor Bars     213
Stator Slots     214
Rotor Bars     217
Use of Databases     217
Alarm Levels     217
Evaluating Data: Basic Steps for Pattern Recognition     218
Common AC Induction Motor Signatures     219
Unbalance and Misalignment     219
Gearbox Fault     219
Classical Rotor Bar Fault     220
Punch Press: Driven Equipment Effects     221
Fan and Belt Faults     221
Coil Movement     222
Static Eccentricity     223
Variable Frequency Drives     223
Chapter 10 Questions     226
Electrical Signature Analysis Pattern Recognition DC Machines     227
DC Troubleshooting Patterns     227
Considerations in DC Analysis     230
Chapter 11 Questions     234
Developing an EMD Program      235
Concepts of the Program     236
Key Performance Indicators     238
RCMM Team     239
Considerations in Selecting Equipment     240
Defining Motor Management Programs     240
Company Mission     242
The RCM-Based Approach for Motor Management     242
Selecting CBM Equipment     245
Advanced Transformer Analysis with the ALL-TEST IV PRO 2000     247
Single Phase Transformer Testing     247
Procedure     247
Test Results     248
Three Phase Transformer Testing     249
Procedure     249
Testing Notes and Limits     250
Evaluation of Capacitance in Motor Circuit Analysis Findings     251
MCA Tables for TTFE Baselines     259
Determining Testing Frequency     261
Stator Slot and Rotor Bar Tables     263