Agenda
• Overview of SKF CMC-Fort Collins solutions and
capabilities
• Why perform static and dynamic motor analysis
• Discuss insulation system and dielectric strengths
• Show where and how motors typically fail
• How SKF static motor test products determine condition
of insulation and motor circuit
• How SKF dynamic motor monitoring products
determine issues with incoming power, motor, and load
(mechanical or electrical problems)
CMC-Fort Collins solution portfolio
Electric motor management drives predictive maintenance
and quality assurance programs
SKF Online Motor Analysis
System NetEP
SKF Dynamic Motor Analyzer
EXP4000
SKF Static Motor Analyzer
Baker AWA-IV
Why perform static and dynamic
motor analysis
Cost savings
• Reduce unscheduled downtime
• Perform root-cause analysis
• Reduce energy costs
• VFD: analysis
• Motor quality assurance
• Reduce troubleshooting time
Complete system analysis
MCC
Load
Motor
Motor failure causes
IEEE Study
EPRI Study
Bearing
44%
Other
22%
Bearing
41%
Rotor
8%
Stator
26%
Other
14%
Rotor
9%
Stator
36%
Motor failure causes: IEEE study
100%
80%
Electrical Fault
Mechanical Breakage
Insulation Breakdown
Overheating
60%
40%
20%
0%
Bearing
Winding
Motor insulation systems and dielectric
strengths
The nature of motor insulation
• Insulation system strengths
• Motor failures: how and where?
• It’s never a matter of if a motor will fail electrically… it’s
a matter of when
Progression to electrical motor failure
• Dielectric strength of a newly-manufactured
motor is very high
Progression to electrical motor failure
• Motor will see normal aging from:
– Thermal (excessive heat degrades
insulation)
– Chemical (contaminants, including water)
– Mechanical (vibration, friction, wearing)
Progression to electrical motor failure
• Turn-to-turn dielectric strength falls
below level of switching surges
• Arcing occurs when motor starts up
Progression to electrical motor failure
(4) Insulation begins to deteriorate much faster
(5) T-T Dielectric Strength drops below operating voltage
• The short fuses
(6) Transform action causes high induced current - high heat 16-20
time full load amps
(7) Rapid Failure (Typically Minutes)
Turn-to-turn failures
• 80 percent of electrical motor failures start as turn-to-
turn fault
• Most will ultimately fail to ground, but the root cause is
most often a turn-to-turn failure
– General Electric
Why most failures begin as turn-to-turn shorts
• Turn insulation is the weakest/thinnest insulation in the
motor
• Chemical deposits break down the insulation
• Movement from startups rubs turns together, causing
friction wear
– D.E. Crawford, General Electric
Static motor analyzers assess insulation
and motor circuit condition
Value of surge tests
• The surge test is the only consistently reliable method
of detecting weak insulation between motor winding turns
• The ability to find such weaknesses before the motor
fails allows the operator to be predictive
Surge testing
• Field tests on fully assembled, powered-down motors can
find weak insulation (PPM, QA, TS), e.g.:
– Turn-to-turn
– Phase-to-phase
– Coil-to-coil
Surge testing
• In-shop testing (with rotor removed) can find:
– Weak insulation, e.g. turn-to-turn, phase-to-phase, coil-to-coil
(QA, TS, PPM)
– Reversed coils (QA)
– Turn-to-turn shorts (QA,)
– Unbalanced turn counts (QA)
– Different or uneven-sized copper wire (QA)
– Shorted laminations (QA)
Surge ring
Weak turn-to-turn insulation
432-1992 IEEE guide for insulation maintenance for rotating electric machinery (5 hp to less than
10 000 hp) and IEEE Guide for Insulation Maintenance for Rotating Electric Machinery (5 hp to
less than 10,000 hp)
Scope
This insulation maintenance guide is applicable to industrial air-cooled rotating electric machines rated from 5 hp to 10 000 hp. The
procedures detailed herein may also be useful for other types of machines.
7.4 Interturn Insulation Tests
Film insulation usually provides high dielectric strength but, in many cases, the interturn insulation on motor coils is porous in nature.
Fibrous insulation effectively provides a physical separation of the turns of the order of 0.010 to 0.025 in (0.25Ð0.635 mm) for motors,
and the electric strength between the turns is essentially provided by the insulating value of the gas (air, hydrogen, etc.) contained
between these Þbers. Micaceous insulations are commonly used in high-voltage machines.
To provide a useful service in checking the adequacy of the insulation between turns, the test level selected must be greater than the
minimum sparking potential of the air at the minimum permissible spacing. The test potential will often, therefore, be several times normal
operating volts per turn. A test of about 500 V rms per turn is considered average for a new machine, while for maintenance tests
potentials of one-half to two-thirds of the new coil turn test, eight to ten times normal operating volts per turn, are usually considered
adequate to provide insurance from the possibilities of marginal insulation and contains allowance for switching transients and for surges
likely to be encountered in service.
The normal operating volts per turn are often up to about 30 V for motors, while turbine and water-wheel generators are substantially
above that value. The test methods used include forms of surge comparison tests. A steep-front surge is applied to all or part of a
winding, or by induction to individual coils within a winding. The resultant waveforms are viewed on an oscilloscope screen and
interpretation of the patterns or amplitudes permits detection of short-circuited turns. The surge comparison test applied directly to the
winding terminals is limited, in the case of windings consisting of many coils in series, by the magnitude of the voltage that can be applied
to the ground insulation without exceeding its specified test voltage. This limitation can be overcome by placing a surge coil in the bore
over the coil to be tested and by applying directly into it a voltage appropriate to the induced volts per turn required in the stator coil. For
additionalinformation on procedures and requirements for interturn insulation tests, see IEEE Std 522-1992 [10]. See [B14] for detailed
information on surge comparison testing.
IEEE Standard for Petroleum and Chemical Industry — Severe Duty, Totally-Enclosed FanCooled (TEFC) Squirrel Cage Induction Motors — up to and including 370 kW (500 hp)
d) The 2300 V and 4000 V designs shall use vacuumpressure-impregnated form windings, capable of
withstanding a voltage surge of 3.5 per unit at a rise time
of 0.1 µs to 0.2 µs and of 5 per unit at a rise time of 1.2
µs or longer. (One per unit equals 0.8165 V L-L .) The
test method and instrumentation used shall be per IEEE
Std 522-1992. When specified by the purchaser, this
requirement shall also apply to form windings supplied for
voltages 575 V and below on motors rated above 150 kW
(200 hp).
Motor tests
• Low-voltage motor circuit measurements
–
–
–
–
–
Winding resistance (Pdm, QA, TS)
Inductance (QA)
Impedance (QA)
Capacitance (Pdm)
Phase angle (QA)
• Low-voltage DC tests
– Megohm test (Pdm, TS)
– PI (polarization index) test (Pdm)
• High-voltage tests
– Step-voltage test (Pdm, QA, TS)
– Surge test (Pdm, QA, TS)
Resistance tests
• Balance between phases (Pdm, QA, TS)
–
–
–
–
–
# of turns per phase (QA)
Diameter copper (QA)
High resistance connections (PPM, TS, QA)
Turn-to-turn shorts (TS, QA, PPM)
Turn-to-turn opens (TS, QA,)
• Trending
Inductance, impedance and phase-angle tests
• Balance between phases (QA)
–
–
–
–
–
# of turns per phase (QA
Diameter copper (QA)
Turn-to-turn shorts (QA)
Turn-to-turn opens (QA)
Reversed coils
Capacitance measurement
• Value:
− Confirms wet and/or dirty motor (Pdm)
− Provides valuable trend data (Pdm)
− Compares measurements with megohm and PI readings before a
motor is pulled
Megohm test
• Megohm meters are useful to:
– Determine if the motor has failed to ground (TS)
– Confirm a dirty motor (surface leakage) (PPM)
– Acquire useful trending data (PPM)
Insulation testing
• Megohm meters can not:
–
–
–
–
Determine if a motor is good
Determine a Turn-to-Turn Fault
Determine a Open Phase
Determine a Phase-to-Phase Fault
Polarization index (PI), dielectric absorption (DA) tests
• These tests are effective at detection of:
– Deteriorated ground wall insulation (PPM, QA)
– Dry-rotted, hard, brittle ground wall insulation (PPM, QA)
– Moisture and contamination
Step-voltage tests
• Highly reliable for detection of:
– Weak ground wall insulation (PPM, QA, TS)
– Cable insulation (PPM, QA, TS)
Case study: detection of weak turn-to-turn insulation
Low-voltage tests reveal that all is “good”
Case study: detection of weak turn-to-turn insulation
Low-voltage tests reveal that all is “good”
Case study: detection of weak turn-to-turn insulation
• Surge test is the only test capable of finding weak
insulation, turn-to-turn
– Phase 1 and 2 tests reveal they are good:
Case study: detection of weak turn-to-turn insulation
• Phase 3 test reveals weak
insulation, turn-to-turn at about
1,000 volts
• This is not a turn-to-turn short!
• If it was the result of a winding
resistance test, it would be
unbalanced, and it is not
• No other test method can
accurately find this issue
Case study: contamination of J-box
• Motor stats:
– 7200 Volt
– 1000 hp
– 3600 RPM Motor
Case study: contamination of J-box
Case study: contamination of J-box
Case study: contamination of J-box
Case study: contamination of J-box
Results after the J-Box was cleaned
Summary of J-box contamination case study
• A problem could only be detected with a test voltage
elevated above operational voltage
• Voltage spikes could track and cause a failure
Case study: detection of unstable ground wall insulation
• Performed a step-voltage test at higher voltage
• Motor stats:
– 4160 Volt motor
– 300 hp
– 1770 rpm speed
• Tested four identical motors at a power plant
Case study: detection of unstable ground wall insulation
Case study: detection of unstable ground wall insulation
Case study: detection of unstable ground wall insulation
Case study: detection of unstable ground wall insulation
Case study: detection of unstable ground wall insulation
• Last step at 8,960 Volts revealed unstable ground wall
insulation
• The step-voltage test allowed the operator to view and
trend the current leakage
Dynamic products determine power,
motor, load and mechanical issues
Dynamic motor analysis
SKF Online Motor Analysis
System NetEP
SKF Dynamic Motor Analyzer
EXP4000
Safety and connections: low voltage (less than 600 V)
Load
Breaker
Motor
MCC
Exp
Step one:
Step two:
Step three:
Step four:
Step five:
Step six:
Running motor
STOP motor
Connect MPM
Run and test
STOP motor
Disconnect MPM
Safety and connections: medium- and high-voltage (more
than 600V) connect into secondary PTs and CTs
Load
Breaker
Motor
CTs
PTs
Step one:
Motor is running
Step two:
Connect EXP4000 CTs
Step three: Connect EXP4000 PTs
EXP4000
Data acquisition: safe, fast and easy with SKF EP1000
Breaker
Motor
CTs
PTs
EP
One of 700+ EPs at a site
EXP4000
First Energy
RC Pump
SKF Online Motor Monitoring System - NetEP
• NetEP is a fully-automated, network-connected,
electric motor monitoring system. It collects health
and performance data of electric motors at rapid
intervals, 24 hours a day, 365 days a year.
• The NetEP is a permanently-installed system.
Permanent voltage and current sense connections
are required for each motor.
• The NetEP monitors over 40 electrical
parameters of electric motors and compares the
results to limits, displaying alerts if limits have
been exceeded.
• The NetEP can be configured, monitored and
operated 24/7 from any Internet network
connection (anywhere in the world).
SKF Online Motor Monitoring NetEP - Overview
• NetEP – Networked Electrical Processor
• Monitors up to 32 motors (96 CTs)
–
–
–
–
5A to 2000A
Calibrated, from CMC-FC
Up to 150’ CT signal runs on CAT 5 cable
25 kHz signal acquisition
• Up to 7 different voltage busses
–
–
Up to 1000 V direct input, or PTs.
Line-to-line, line-to-neutral, external disconnect required
• MCC mounted box
–
–
20” x 30” x 8”, ~ 65 lbs
CAT III, NEMA 12 Enclosure
• LAN and AC power (110V – 240V) required
• Computers for data storage and network based monitoring
–
Provided by customer (IT compatibility)
• Test all 32 motors every 10 sec (basic motor monitoring)
Power quality analysis
• PQ capabilities
– Voltage and current level, unbalance distortions
– Kvars, KVA, KW’s, power factor, crest factor, harmonic bar
chart, etc.
Motor overheating
I2R Losses
Motor Currents
100% rated Current
100% rated Temperature
110% rated Current
121% rated Temperature
Voltage unbalance and harmonic distortions
• Voltage quality
• NEMA derating
Effective s.f.
% Load
Eff. s.f. =
% NEMA derating
Test station 300 hp 3570 rpm
Motor performance: service factor and temperature
Temperature (C)
Horsepower Full Load 1.15 SF 1.25 SF
10
49
64
77
20
56
75
91
50
75
102
128
100
64
80
94
69
89
106
200
- Courtesy U.S. Motors
Effective service factor
All OK?
Pulp & paper industry:
Operating RMS values
Voltage Level
658.2 V
Current Level
378.4 A
Load Level
312.6 kW
99.7%
91.4%
78.1%
Voltage Unbalance
Voltage Distortion
3.66%
9.80%
NEMA derating %
Eff. s.f.
0.6
1.28
Power quality analysis
Importance
• Poor power quality causes increase heat
• For every ten degrees rise in temperature the life of the motor is reduced
in half.
Motor condition: broken rotor bar
Fan 1 hp 1740 rpm
Torque analysis
• Great tool to determine electrical vs. mechanical issues
(solves disputes between mechanics and electricians)
– The load is what causes more or less torque from the motor
– If a torque signature looks out of the ordinary, the problem is
most likely with the load (e.g., a fan, impeller, etc.)
Torque signature
4160V submersible pump
Mechanical FFT analysis
• Diagnose mechanical
issues from the MCC
–
–
–
–
Bearing
Outer race
Inner race
Cage fr.
• Fan unbalance
VFD: variable frequency drive analysis
• Benefits
–
–
–
–
Tune in drive
Load analysis
Faulty IGBT’S
Feedback loop issues
Transient analysis
• Set up short, medium, and
long range trip settings
• Set up soft starts
• Diagnose pump and fan
issues
–
–
–
–
Worn impellers
Binding pumps
Power issues
Rotor issues
Continuous monitoring software
Excellent troubleshooting tool
Organizations that back SKF CMC-FC testing methods
IEEE 522
IEC 34-15
NEMA MG1
NFPA 70B
EASA
Faults the EXP4000 and Baker AWA-IV will identify
Power quality
Poor-performing transformers
Short, medium, long, range trip settings
Connection issues (junction box in motor)
Lead-line insulation deterioration
Turn-to-turn, phase-to-phase, coil-coil insulation
weaknesses
Ground wall insulation
• Weakness
• Dirt
• Moisture
• Dry rot, brittle
• Cracks
Motor circuit
• Turn–to-turn shorts, opens
• Reversed coils
• Phase unbalanced (turn count)
• Phase unbalanced (wire size)
Rotor
• Cracked bars
• Poor welds
• Broken bars
• Eccentricity (dynamic, static)
Loading Issues
• Overload
• Process
Mechanical
• Bearing faults
• Misalignment
• Fan unbalances
• Belt frequencies
• Worn Impellers
• Gear mesh frequencies
VFD
• Power quality
• Shorted IGBT’s
• Feedback loop
• Process information
• Tuning /setup
Soft Start
• Tuning /setup
• Troubleshooting
Easy automatic analysis of results
Summary
• Dynamic motor monitoring and analysis provides
information about the power condition, the load and the
motor
• Static motor testing measures the integrity of the
motor’s insulation system and motor circuit
• Together they present a comprehensive picture of the
motors health, and provide information required to
accurately diagnose potential failures and avert
unplanned downtime. Motor quality assurance and
troubleshooting capabilities can be realized with the use
of the Baker AWA-IV and EXP4000
Thank you!