Methodology of motor predictive monitoring
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Transcript of Methodology of motor predictive monitoring
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Methodology of Motor Predictive Monitoring.
This presentation covers the methodology of Motor Predictive Monitoring, the
background to motor failure and the Instruments available to achieve correct analysis for
both on line (live) and off line motors.Whitelegg are UK and Ireland agents for Baker Inc (anSKF Company)
On-Line or Dynamic Testing
(Explorer Monitoring)
Explorer
Off-Line or Static Testing
(Advanced Winding Analyzer)
AWA
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Cost savings
Reduced unscheduled downtime through MPM
(Motor Predictive Monitoring)
Indicates root cause analysis
Save s of energy costs
VFD: Analysis
Motor Quality Assurance
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Electrical Motor Management
Programme
The Question is not if a Motor will fail electrically,
it is
(1) Dielectric Strength of a new motor is very high
(2) All Motor will see normal ageing
Thermal
Chemical Mechanical
(3)T-T Dielectric Strength falls below
level of switching surges
Arcing occurs when motor starts up
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(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)
80% of electrical motor failures start as turn-to-turn fault
Most will fail to ground but the root cause will be turn toturn failure
General Electric Paper
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Turn insulation is the weakest insulation in the motor
Chemical deposits breakdown the insulationMovement from start up rubs the turns together causing
wear source: D.E. Crawford\General Electric
The Surge Test is the only method available to find weak
insulation between the turns. Thus allowing the operatorto be predictive.
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Field Testing Can Find-
Weak insulation (PPM, QA, TS)
Turn-To-Turn
Phase-To-Phase
Coil-To-Coil
In-Shop Testing (Rotor Removed)
Can find-
Weak insulation turn to turn, phase to phase, coil to coil (QA, TS, PPM)
Reversed coils (QA)
Turn-To-Turn shorts (QA,)
Unbalanced turn count (QA)
Different size copper wire (QA)
Shorted laminations (QA)
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Scope
This insulation maintenance guide is applicable to industrial air-cooled rotating electric machines ratedfrom 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 onmotor coils is porous in nature. Fibrous insulation effectively provides a physical separation of the turns ofthe order of 0.010 to 0.025 in (0.250.635 mm) for motors, and the electric strength between the turns isessentially provided by the insulating value of the gas (air, hydrogen, etc.) contained between thesebers. 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 levelselected must be greater than the minimum sparking potential of the air at the minimum permissiblespacing. The test potential will often, therefore, be several times normal operating volts per turn. A test ofabout 500 V rms per turn is considered average for a new machine, while for maintenance tests potentialsof one-half to two-thirds of the new coil turn test, eight to ten t imes normal operating volts per turn, areusually considered adequate to provide insurance from the possibilities of marginal insulation andcontains 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-wheelgenerators are substantially above that value. The test methods used include forms of surge comparisontests. A steep-front surge is applied to all or part of a winding, or by induction to individual coils within awinding. The resultant waveforms are viewed on an oscilloscope screen and interpretation of the patternsor amplitudes permits detection of short-circuited turns. The surge comparison test applied directly to thewinding terminals is limited, in the case of windings consisting of many coils in series, by the magnitude ofthe voltage that can be applied to the ground insulation without exceeding its specified test voltage. Thislimitation can be overcome by placing a surge coil in the bore over the coil to be tested and by applyingdirectly into it a voltage appropriate to the induced volts per turn required in the stator coil. For additional
information on procedures and requirements for interturn insulation tests, see IEEE Std 522-1992 [10].See [B14] for detailed information on surge comparison testing.
d) The 2300 V and 4000 V designs shall use vacuum-pressure-
impregnated form windings, capable of withstanding a voltage surge
of 3.5 per unit at a rise time of 0.1 s to 0.2 s and of 5 per unit at a
rise time of 1.2 s 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).
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Winding Resistance (PPM, QA, TS)
Meg-ohm test (PPM, TS)PI (polarization test) (PPM, QA)
Step Voltage Test (PPM, QA, TS)
Surge Test (PPM, QA, TS)
Balance between phases (PPM, 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
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Meg-Ohm-Meter
It Can:
Determine if the motor has failed to ground. (TS)
Dirty motor (Surface leakage) (PPM)
Trending (PPM)
Meg-Ohm-Meter
It Can Not
Determine if a motor is good
Determine a Turn-to-Turn Fault
Determine a Open Phase
Determine a Phase-to-Phase Fault
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Can find-
Deteriorated ground wall insulation (PPM, QA)
Dry-rotted, hard, brittle ground wall insulation (PPM, QA)
Moisture and Contamination
Can find-
Weak Ground wall insulation (PPM, QA, TS)
Cable insulation (PPM, QA, TS)
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Low Voltage Tests Show all good
Low Voltage Tests Show all good
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Surge test is the only test capable of finding weak
insulation turn to turn
Phase 1 & 2 are good
Phase 3 shows weak insulation TurnTurn at about 1,000 volts.
This is not a TurnTurn Short
If it was the winding resistance would be unbalanced and it is not
No other technology can find this fault
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480 Volt
60 Hp1760 RPM
Low voltage Tests show good
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White wave form shows the frequency shift when the
weak insulation occurred
1490 volts is where the weak insulation occurred on this
phase
Motor
7200 volt
1000 Hp
3600 RPM Motor
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Results after the J-Box was cleaned
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Only by elevating the voltage above operating voltage did
we see a problem
Voltage spikes could track and cause a failure
4160 Volt Motor
300 HP
1770 speedTested 4 identical motors at a power plant
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Last step at 8,960 Volts shows unstable ground wall
insulation
The step test allows the operator to see and trend the
current leakage
Dynamic Motor Monitoring
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Standard Connection
Install PPE
Open cabinet Connect CTs and Voltage Clips
Less Than 600 V connect to bottom of starter
Greater Then 600 Volts Connect into Secondary PTs and CTs
Time for connection 4 Min
Testing Time
1 Sample 1560 Seconds
Depends on rates and acquisition time
See next slide
Standard Connection
Install PPE
Open cabinet
Connect CTs and Voltage Clips
Less Than 600 V connect to bottom of starter
Greater Then 600 Volts Connect into Secondary PTs and CTs
Time for connection 4 Min
Testing Time
1 Sample 1560 Seconds
Depends on rates and acquisition time
See next slide
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Motor
MCC
LoadBreaker
Step one: Running motor
Step two: STOP motor
Step three: Connect MPM
Step four: Run and test
Step five: STOP motor
Step six: Disconnect MPM
Exp
Motor
CTs
Breaker
PTs
EP
Explorer
First EnergyRC Pump
1 of 700+ EPs at one customer
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PQ Capabilities
Voltage and Current level, unbalance distortions
Kvars, KVA, KWs, Power factor, Crest factor, Harmonic bar chart ect.
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Eff. s.f.
% NEMA derating
% Load
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Temperature (C)
Full Load 1.15 SF 1.25 SF49 64 77
56 75 91
75 102 128
64 80 94
69 89 106
Horsepower10
20
50
100
200
* Courtesy U S Motors
Operating RMS values
Voltage Level 658.2 V 99.7%
Current Level 378.4 A 91.4%
Load Level 312.6 kW 78.1%
Voltage Unbalance 3.66%
Voltage Distortion 9.80%
NEMA derating % 0.6
Eff. s.f. 1.28
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Importance
Poor power quality causes increase heat
For every ten degrees rise in temperature the life of the motor is reducedin half.
Fan 1 hp 1740 rpm
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Great tool for Separating electrical and mechanical
issues (solve disputes between mechanics and
electricians) Reason 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 in the load
4160V submersible pump
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Diagnose mechanical issues from
the MCC
Bearing Outer Race
Inner Race
Cage fr.
Fan Unbalance
Ect.
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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
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IEEE 522
IEC 34-15NEMA MG1
NFPA 70B
EASA
Power Quality
Poorly performing Transformers
Short, medium, long, range trip settings
Connection issues (Junction Box, In motor)
Lead Line Insulation deterioration
Turn-Turn, Phase-Phase, Coil-Coil insulationweakness
Ground Wall Insulation
Weakness
Dirt
Moisture
Dry Rotted, Brittle
Cracks
Motor Circuit
TurnTurn Shorts, Opens
Reversed Coils
Phase Unbalanced (turn count)
Phase Unbalanced (wire size)
Rotor
Cracked Bars
Poor Welds
Broken Bars Eccentricity (Dynamic, Static)
Loading Issues
Over load
Process
Mechanical
Bearing faults
Miss Alignment Fan Unbalances
Belt frequencies
Worn Impellers
Gear Mesh Frequencies
VFD
Power Quality
Shorted IGBTs
Feed Back loop
Process Information
Tuning / Set up
Soft Start
Tuning / Set up
Trouble shooting
Ect.
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Power Quality
Poorly performing Transformers
Short, medium, long, range trip settings
Connection issues (Junction Box, In motor)Lead Line Insulation deterioration
Turn-Turn, Phase-Phase, Coil-Coil insulationweakness
Ground Wall Insulation
Weakness
Dirt
Moisture
Dry Rotted, Brittle
Cracks
Motor Circuit
TurnTurn Shorts, Opens
Reversed Coils
Phase Unbalanced (turn count)
Phase Unbalanced (wire size)
Rotor
Cracked Bars
Poor Welds
Broken Bars
Eccentricity (Dynamic, Static)
Loading Issues
Over load
Process
Mechanical Bearing faults
Miss Alignment
Fan Unbalances
Belt frequencies
Worn Impellers
Gear Mesh Frequencies
VFD
Power Quality
Shorted IGBTs
Feed Back loop
Process Information
Tuning / Set up
Soft Start
Tuning / Set up
Trouble shooting
Ect.
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Explorer (On-Line) testing provides information about the
power condition, the load and the motor.
AWA (Off-Line) testing measures the integrity of the
motors insulation system and motor circuit
Together they present a picture of the motors health and
provide information required to accurately diagnose and
predict imminent failures. Increasing motor quality
assurance and trouble shooting capabilities will be
realised with the utilisation of the AWA and Explorer
Questions?
For further information, please visit www.whitelegg.com
Or contact
Whitelegg Machines Ltd, 19 Crompton Way, Manor Royal, Crawley, West Sussex RH10 9QR,
UK Tel: +44 (0) 1293 526 230 | Fax: +44 (0) 1293 538 910 | Email: [email protected]
http://www.whitelegg.com/http://www.whitelegg.com/http://www.whitelegg.com/http://www.whitelegg.com/