On-li n-line Mot otor or Mon onit itori oring ng Joe Geiman - - PowerPoint PPT Presentation

On-li n-line Mot

• tor
• r Mon
• nit

itori

• ring

ng

Joe Geiman Joe Geiman Baker Instrument Co. Baker Instrument Co.

What are we really after? Induction motor and VFD applications

 

Reduce unscheduled downtime Reduce unscheduled downtime

 

Indicates root cause analysis Indicates root cause analysis

 

Save $ $ $ Save $ $ $

Motor Failure Areas:

IEEE Study EPRI Study

Motor Failure Areas:

IEEE Study EPRI Study

Bearing 44% Rotor 8% Other 22% Stator 26% Bearing 41% Other 14% Rotor 9% Stator 36%

Motor Failure Causes:

IEEE Study

Motor Failure Causes:

IEEE Study

0% 20% 40% 60% 80% 100%

Bearing Winding

Electrical Fault Mechanical Breakage Insulation Breakdown Overheating

Safety and Connecting: Low Voltage (Less than 600V)

Motor MCC Load

Breaker

Step one: Running motor Step two: STOP motor Step three: Connect Explorer Step four: Run and test Step five: STOP motor Step six: Disconnect Explorer Explorer

Safety and Connecting: Medium and High Voltage (More than 600V)

Motor Load

CTs

Breaker

Step one: Motor is running Step two: Connect Explorer CTs Step three: Connect Explorer PTs

Explorer

PTs

Motor

CTs

Breaker

PTs

EP

Explorer

First Energy RC Pump

1 of 700+ EPs at one customer

Acquire Data: Safe, Fast & Easy W/ EP-1

Power Quality Analysis

  PQ Capabilities

PQ Capabilities

  Voltage and Current level, unbalance

Voltage and Current level, unbalance distortions distortions

  Kvars

Kvars, KVA, KW’s, Power factor, Crest , KVA, KW’s, Power factor, Crest factor, Harmonic bar chart factor, Harmonic bar chart ect ect. .

Motor Overheating

  I

I2

2R Losses

R Losses Motor Currents Motor Currents

  100% rated Current

100% rated Current 100% rated Temperature 100% rated Temperature

  110% rated Current

110% rated Current 121% rated Temperature 121% rated Temperature

Fan 1 hp 1740 rpm

Motor Condition: Broken Rotorbar

Rotorbar Frequency:

slip Synchronous rotor bar freq. % [RPM] [Hz]

0.1 1798.2 59.88 0.2 1796.4 59.76 0.3 1794.6 59.64 0.4 1792.8 59.52 0.5 1791 59.4 0.6 1789.2 59.28 0.7 1787.4 59.16 0.8 1785.6 59.04 0.9 1783.8 58.92 1.0 1782 58.8

 

. . . .

slip 2 1

synch

• perat

synch fund rotorbar

RPM RPM RPM s s f f      

Depends on SLIP!

• Harder to assess with lesser load
• Harder to assess with bigger motor
• Harder to assess with more efficient motor

Increasing Lines of Resolution: Increasing Lines of Resolution:

New Rotorbar y-axis Scale

                   A mA dB l fundamenta signal dB res 300 42 log 10 5 . 38 log 10 ] .[ down' dB '

Good Rotor Bar

Bad Rotor Bar

Case Study 1

  2A High Pressure Pump

2A High Pressure Pump

  Problem

Problem

  Serious vibration

Serious vibration

  Vibration Reading

Vibration Reading

• High 7200

High 7200

• Turn off motor 7200 peek disappears

Turn off motor 7200 peek disappears

  Electricians do not believe it could be a rotor bar

Electricians do not believe it could be a rotor bar

• They have never seen a rotor problem

They have never seen a rotor problem

• Electricians have no way to confirm or deny the

Electricians have no way to confirm or deny the allegations of the mechanics allegations of the mechanics

Show Data

  2A high Pressure Pump

2A high Pressure Pump

  Broken Rotor Bar

Broken Rotor Bar

  1C high Pressure Pump

1C high Pressure Pump

  Good Rotor Bar

Good Rotor Bar

2A High Pressure Pump Broken Rotor Bar

2A High Pressure Pump Broken Rotor Bar

1C High Pressure Pump Good Rotor Bar (comparison)

1C High Pressure Pump Good Rotor Bar (comparison)

Conclusion 2A High Pressure Pump

  Recommendation to customer

Recommendation to customer

  It appeared to be a broken

It appeared to be a broken

  All thought, only slightly into the caution

All thought, only slightly into the caution we questioned how saver the problem we questioned how saver the problem was was

Results 2A High Pressure Pump 3 Broken Rotor Bars

Results 2A High Pressure Pump 3 Broken Rotor Bars

Case Study 2 4a PA Fan

  Problem Slight vibration

Problem Slight vibration

Broken Rotor Bar

Broken Rotor Bar

Case Study 3

  Rotor Issue

Rotor Issue

  Show need for higher acquisition

Show need for higher acquisition

  Show other places in spectrum to

Show other places in spectrum to represent or confirm rotor issues represent or confirm rotor issues

Low Resolution Data No Assessment Can Be Made

Low Resolution Data No Assessment Can Be Made

High Resolution Data Assessment Can Be Made

High Resolution Data Assessment Can Be Made

Results

  Inspection found brazing issues at the

Inspection found brazing issues at the end ring causing high resistance joints. end ring causing high resistance joints.

Epoxy Melting Off Rotor Bars Representing Excessive Heat

Cracked End Ring (Case Study 4)

Motor Current Signature Analysis Values From Technical Associates.

  54 – 60 dB

Excellent 54 – 60 dB Excellent

  48 – 54 dB

Good condition 48 – 54 dB Good condition

  42 – 48 dB

Moderate condition 42 – 48 dB Moderate condition

  36 – 42 dB

Rotor bar crack 36 – 42 dB Rotor bar crack developing or developing or high high resistance joints. resistance joints.

  30 – 36 dB

multiple cracked / broken 30 – 36 dB multiple cracked / broken bars or end – rings bars or end – rings indicated indicated

  < 30

dB multiple cracked / < 30 dB multiple cracked / broken bars or broken bars or end-rings very likely end-rings very likely

Current signature: FFT vs. DFLL

Amplitude: 20dB Amplitude: 60dB

Resolution: 0.13Hz Resolution: 0.005Hz

FFT DFLL

Need: High Amplitude and Frequency Resolution

• Requires constant torque level
• Torque ripple
• Next one breaks sooner
• Current increases
• Temperature increases
• Insulation life shortens
• Typically non-immediate death

Motor Condition: Broken Rotorbar issues

Motor MCC Load

• 1. frequency
• 2. speed
• 3. Torque
• 4. Power
• 5. Voltage
• 6. Current

Chain of events: Cause and effect

N S

F F I I F :

Force

I

: Current : Flux

Calculating Torque:

Flux: Generated by stator Voltage Rotor Current: Monitored with Stator Current

T

T(t) = f( V(t), I(t) )

According to Park’s theory, 1920.

Rotor Stator

Calculating Torque:

 

Explorer showed that not all motors run at constant Explorer showed that not all motors run at constant

• perating condition. The 4 motors at the center display
• perating condition. The 4 motors at the center display

a larger variability to their operation. These are the a larger variability to their operation. These are the locations which’ motors break with unusually high locations which’ motors break with unusually high frequency. frequency.

• The maintenance supervisor noted that some stirring

pool motors (decontamination and recycling process) break with unusually high frequency.

Case study I: Hydro-mechanical resonance. Brewery. Case study I: Hydro-mechanical resonance. Brewery.

Case study I: Hydro-mechanical resonance. Brewery. Case study I: Hydro-mechanical resonance. Brewery.

• The maintenance supervisor noted that some stirring

pool motors (decontamination and recycling process) break with unusually high frequency.

• The Explorer showed that not all motors run at

constant operating condition. The 4 motors at the center display a larger variability to their operation. These are the locations which’ motors break with unusually high frequency.

• The Torque Ripple graphs clarified the source of the
• peration’s variability.

Case study I: Hydro-mechanical resonance. Brewery. Case study I: Hydro-mechanical resonance. Brewery.

Case study I: Hydro-mechanical resonance. Brewery. Case study I: Hydro-mechanical resonance. Brewery.

Corrective action:

4160V submersible pump

Torque Signature:

Torque Ripple vs. Time

Hz s s period time s

• ccurrence

frequency 2 . 3 11 . 73 . 2 _ #    

Torque Ripple vs. Time

Hz s s period time s

• ccurrence

frequency 2 . 3 11 . 73 . 2 _ #    

Torque vs. Frequency: Mechanical Imbalance

• Investigating vibration and torque for

inaccessible loads:

Comparison of Duct-Mounted Vibration and Instantaneous Airgap Torque Signals for Predictive Maintenance of Vane Axial Fans . Comparison of Duct-Mounted Vibration and Instantaneous Airgap Torque Signals for Predictive Maintenance of Vane Axial Fans .

Don Doan

Texas Utilities

Ernesto Wiedenbrug

Baker Instrument Company

Don Doan Don Doan

Texas Utilities Texas Utilities

Ernesto Wiedenbrug Ernesto Wiedenbrug

Baker Instrument Company Baker Instrument Company

Presented in IEEE CMD / 2005 Ulsan, Korea Presented in IEEE CMD / 2005 Ulsan, Korea

Problem Application: Problem Application:

 A Vane Axial Fan’s failure can result in

unplanned outages, health and safety costs, and extensive damage to surrounding equipment.

  A Vane Axial Fan’s failure can result in

A Vane Axial Fan’s failure can result in unplanned outages, health and safety costs, and unplanned outages, health and safety costs, and extensive damage to surrounding equipment. extensive damage to surrounding equipment.

• Vane Axial Fans are common

in nuclear environments

• It is almost impossible to

predict bearing faults for Vane Axial Fans.

• Vane Axial Fans are common

in nuclear environments

• It is almost impossible to

predict bearing faults for Vane Axial Fans. Nuclear Comanche Peak Station TXU Electric

Horizontal Application Vertical Application

Vane-axial Fan Maintenance Challenge: Vane-axial Fan Maintenance Challenge:

 Application frequently called: “Fan-in-a-can”  Impossible to monitor with preferred technology

(vibration on bearing housing)

 Cost prohibitive to issue a “change in design”

for all Vane axial Fans for this Nuclear Power

• Plant. (Nuclear Industry in U.S. average cost per

meter of retrofitted wire > U$ 5,000)

  Application frequently called: “Fan-in-a-can”

Application frequently called: “Fan-in-a-can”

  Impossible to monitor with preferred technology

Impossible to monitor with preferred technology (vibration on bearing housing) (vibration on bearing housing)

  Cost prohibitive to issue a “change in design”

Cost prohibitive to issue a “change in design” for all Vane axial Fans for this Nuclear Power for all Vane axial Fans for this Nuclear Power

• Plant. (Nuclear Industry in U.S. average cost per
• Plant. (Nuclear Industry in U.S. average cost per

meter of retrofitted wire > U$ 5,000) meter of retrofitted wire > U$ 5,000)

Laboratory Investigation: Laboratory Investigation:

 Set up a Vane Axial Fan in a Laboratory, and create:

• Healthy operation (baseline data)
• Advanced Bearing fault (Stage III)

 Gathering Data:

• Vibration data obtained from the bearing housing – preferred

diagnostic method – (used as benchmark of planted faults).

• Accelerometers connected to the outside of the duct.
• Calculated Instantaneous Airgap Torque using Park’s theory.

 Statistical Data Analysis:

• Statistical evaluation using “single sided experiment design”.
• 9 samples needed for certainties exceeding 95% and 90% for

errors type I, and type II, respectively.

  Set up a Vane Axial Fan in a Laboratory, and create:

Set up a Vane Axial Fan in a Laboratory, and create:

• Healthy operation (baseline data)

Healthy operation (baseline data)

• Advanced Bearing fault (Stage III)

Advanced Bearing fault (Stage III)

  Gathering Data:

Gathering Data:

• Vibration data obtained from the bearing housing – preferred

Vibration data obtained from the bearing housing – preferred diagnostic method – (used as benchmark of planted faults). diagnostic method – (used as benchmark of planted faults).

• Accelerometers connected to the outside of the duct.

Accelerometers connected to the outside of the duct.

• Calculated Instantaneous Airgap Torque using Park’s theory.

Calculated Instantaneous Airgap Torque using Park’s theory.

  Statistical Data Analysis:

Statistical Data Analysis:

• Statistical evaluation using “single sided experiment design”.

Statistical evaluation using “single sided experiment design”.

• 9 samples needed for certainties exceeding 95% and 90% for

9 samples needed for certainties exceeding 95% and 90% for errors type I, and type II, respectively. errors type I, and type II, respectively.

Chosen Fan / Motor: Chosen Fan / Motor:

 Motor: Baldor 3.7kW (5hp),

4-pole, 480V.

 Fan: Aerovent 304 mm (24 in).  System used in the Exhaust of

the Electrical Control Room.

  Motor:

Motor: Baldor Baldor 3.7kW (5hp), 3.7kW (5hp), 4-pole, 480V. 4-pole, 480V.

  Fan:

Fan: Aerovent Aerovent 304 mm (24 in). 304 mm (24 in).

  System used in the Exhaust of

System used in the Exhaust of the Electrical Control Room. the Electrical Control Room. Note: The support system of this motor/fan has a long transmission path – which may dampen mechanical signals on their way to the duct. Note: The support system of this motor/fan has a long transmission path – which may dampen mechanical signals on their way to the duct.

The “known good” Signals: The “known good” Signals:

Redundant verification:

 Accelerometers: 100mV/g ICP  Cognitive Systems CV395B Analyzer  Bentley Nevada ADRE 208P  SWANTECH stress wave analysis

Redundant verification: Redundant verification:

 

Accelerometers: 100mV/g ICP Accelerometers: 100mV/g ICP

 

Cognitive Systems CV395B Analyzer Cognitive Systems CV395B Analyzer

 

Bentley Nevada ADRE 208P Bentley Nevada ADRE 208P

 

SWANTECH stress wave analysis SWANTECH stress wave analysis

Additional Instrumentation ensuring constant operating condition:

Airfolow Meters Humidity Meter Thermocouples Current Meters Laser tachometers

Additional Instrumentation ensuring constant operating condition:

Airfolow Meters Humidity Meter Thermocouples Current Meters Laser tachometers

Field-friendly alternative #1:

Duct-mounted Accelerometers

Field-friendly alternative #1:

Duct-mounted Accelerometers

 Vibration Transducers 100mV/g ICP.  Cognitive Systems Spectrum Analyzer  Accelerometers mounted directly at Mounting Rod on the Duct.   Vibration Transducers 100mV/g ICP.

Vibration Transducers 100mV/g ICP.

  Cognitive Systems Spectrum Analyzer

Cognitive Systems Spectrum Analyzer

  Accelerometers mounted directly at Mounting Rod on the Duct.

Accelerometers mounted directly at Mounting Rod on the Duct.

Field-friendly alternative #2:

Torque Signature Analyzer

Field-friendly alternative #2:

Torque Signature Analyzer

 Explorer II (Baker Instrument Company)  Measures 3 currents and 3 voltages at MCC.  Calculates airgap torque (Park 1929).  Obtains operating speed from current and torque

signatures.

 Monitoring Imbalances: 1x mechanical frequencies in

airgap torque spectrum.

  Explorer II (Baker Instrument Company)

Explorer II (Baker Instrument Company)

  Measures 3 currents and 3 voltages at MCC.

Measures 3 currents and 3 voltages at MCC.

  Calculates airgap torque

Calculates airgap torque (Park 1929)

(Park 1929).

.

  Obtains operating speed from current and torque

Obtains operating speed from current and torque signatures. signatures.

  Monitoring Imbalances: 1x mechanical frequencies in

Monitoring Imbalances: 1x mechanical frequencies in airgap torque spectrum. airgap torque spectrum.

• 7.6 grams create 0.39 gm (0.54 oz in) imbalance.
• Comparing amplitudes of 1 x mechanical frequencies

for “unfaulted” vs. “faulted” data.

• 7.6 grams create 0.39 gm (0.54 oz in) imbalance.
• Comparing amplitudes of 1 x mechanical frequencies

for “unfaulted” vs. “faulted” data.

• Start: Precision balanced

fan (baseline).

• Planted Fault: 7.6 grams

imbalance.

• Start: Precision balanced

fan (baseline).

• Planted Fault: 7.6 grams

imbalance.

Fault 1:

Mechanical Imbalance

Fault 1:

Mechanical Imbalance

Comparison of the amplitudes of 29.9Hz (1x mechanical) frequencies for 1 set of balanced data, with one set of imbalanced operation: Comparison of the amplitudes of 29.9Hz (1x mechanical) Comparison of the amplitudes of 29.9Hz (1x mechanical) frequencies for 1 set of balanced data, with one set of frequencies for 1 set of balanced data, with one set of imbalanced operation: imbalanced operation:

Fault 1:

Mechanical Imbalance

Fault 1:

Mechanical Imbalance Results:

Duct Accelerometer: Duct Accelerometer:

• 99% certain that imbalanced data has higher

99% certain that imbalanced data has higher amplitude. amplitude.

• Amplitude is only 6.7% higher.

Amplitude is only 6.7% higher. Conclusion: Conclusion: This method This method “could” “could” be used, but the very low amplitude be used, but the very low amplitude gain renders it unfeasible for maintenance. gain renders it unfeasible for maintenance.

Airgap Torque Method: Airgap Torque Method:

  99% certain that imbalanced data has higher amplitude.

99% certain that imbalanced data has higher amplitude.

  Amplitude is 150 times higher ( >40dB ).

Amplitude is 150 times higher ( >40dB ).

Conclusion: Conclusion: According to this experiment, this method According to this experiment, this method CAN CAN be be used for maintenance. used for maintenance. The large amplitude gain makes it very robust and The large amplitude gain makes it very robust and easy to interpret. easy to interpret. Fault 1:

Mechanical Imbalance

Fault 1:

Mechanical Imbalance Results:

Bearing Signature Analysis

• Mechanical world:

Mechanical world:

  Stage II:

Stage II:

  n

nm

m = Mechanical (shaft) speed

= Mechanical (shaft) speed i,k i,k = 1,2,3,… = 1,2,3,…

• Electrical world:

Electrical world:

  Stage II:

Stage II:

  n

nfund

fund = fundamental electrical frequency

= fundamental electrical frequency i,k i,k = 1,2,3,… = 1,2,3,…

m

n 2 k BPFO i s Frequencie Fault     

fund.

n 2 k BPFO i s Frequencie Fault     

Motor Failure Areas:

Bear earings ings

Motor Failure Areas:

Bear earings ings

• harm. * BPFO 2 * RPM

Known Good Bearing Known Outer Race Defect

Torque Spectra

BPFO Controlled Lab Test … how it works

Electrical Frequencies Removed Electrical Frequencies Removed Marking 1 * BPFO Adding Electrical Harmonic Sidebands

Signal Quality: Signal Quality:

• harm. * BPFO 2 * RPM

Torque (Nm) Current (A) RMS 0.5 5 Signal 0.025 0.0022 Noise 0.0012 0.0005

Torque S/N = 4.8 * better Torque S/RMS = 125 * better “It can be found” “It is in your face”

4 pole 5hp

Eccentricity in Spectrum:

• Location:

Location:

• “1x” types:

“1x” types:

• Current signals:

Current signals: f ffund.

• fund. ±

± f fmech.

mech.

• Torque signals:

Torque signals: f fmech.

mech.

• - “Bar-pass” types:
• “Bar-pass” types:
• Current signals:

Current signals: n n · · f fmech.

• mech. ±

± 1 1 · · f ffund.

fund.

(hopefully there) (hopefully there)

• Torque signals:

Torque signals: n n · · f fmech.

mech.

(many times not (many times not there) there)

• 4-pole motor.
• 1x = just below 30Hz.

rpm Hz

s

8 . 1768 60 48 . 29

min 



Eccentricity, Torque Signature:

“1 x” location

Eccentricity, Current Signature: Eccentricity, Current Signature:

“1 x” location “1 x” location

 

rpm Hz

s

2 . 1765 60 58 . 30 60

min 

 

• 4-pole motor.
• 1x = just above 30Hz.

Eccentricity, Torque Signature: Eccentricity, Torque Signature:

“Rotorbar Pass Frequency” location “Rotorbar Pass Frequency” location

• 2-pole motor. 2nd peak @ freq. just below Harmonic.
• 1920Hz / 60Hz = 32bars (1920Hz is synchronous rotorbar pass frequency)

rpm Hz f Hz bars Hz

s mech

5 . 3593 60 89 . 59 89 . 59 32 56 . 1916

min .

   

Eccentricity, Current Signature:

“Rotorbar Pass Frequency” location

• 2-pole motor.
• 1860Hz / 60Hz + 1 = 32bars

rpm Hz f Hz bars Hz Hz

s mech

5 . 3593 60 89 . 59 89 . 59 32 60 51 . 1856

min .

    

“1x” locations

# of Poles Synchronous 1% slip "1x" Torque "1x" Current [RPM] [RPM] [Hz] [Hz]

2 3600 3564 59.4 0.6 4 1800 1782 29.7 30.3 6 1200 1188 19.8 40.2 8 900 891 14.85 45.15 10 720 712.8 11.88 48.12 12 600 594 9.9 50.1

. elec. 1 mech fund x

f f f  

. trq. 1 mech x

f f 

Comparing Ieccent. with Teccent.

• T

Teccent.

• eccent. at “expected” frequency

at “expected” frequency

• I

Ieccent.

• eccent. at “expected” frequency – 60Hz.

at “expected” frequency – 60Hz.

• T

Teccent.

• eccent. -28.43 dB relative amplitude.
• 28.43 dB relative amplitude.
• I

Ieccent.

• eccent. -34.9 dB relative amplitude.
• 34.9 dB relative amplitude.
• Teccent. is at the understandable location.
• Teccent. has a 4.5 times larger signal.

Demodulated Signals:

Tor

• rque

que vs. Cur urrent ent

Demodulated Signals:

Tor

• rque

que vs. Cur urrent ent

Demodulated Torque Demodulated Current 1* RPM 2* RPM 1* RPM 2* RPM Bad Motor #1 Bad Motor #2 Good Motor #1 Good Motor #2 3.47E-05 7.94E-05 0.00324 0.03150 4.26E-05 7.96E-05 0.00398 0.03091 2.96E-05 1.35E-05 0.00245 0.03109 3.46E-05 1.42E-05 0.00308 0.03057 Factor 1.20 5.90 1.31 1.01

Conclusions:

• Demodulated Current method does not agree with vibration’s methods.
• Demodulated Torque reacts like vibration’s methods.
• This method is independent of Motor design.
• This method does not disagree with IEEE motor scientist’s research.

Case study II: Cooling tower fan and gear signatures. Coal-fired power plant. Case study II: Cooling tower fan and gear signatures. Coal-fired power plant.

Input Shaft Freq. Intermediate Shaft Freq. Output Shaft Freq. Blade Pass Freq.

Case study II: Cooling tower fan and gear signatures. Coal-fired power plant. Case study II: Cooling tower fan and gear signatures. Coal-fired power plant.

1st Mesh Frequency 2nd Mesh Frequency

Case study II: Cooling tower fan and gear signatures. Coal-fired power plant. Case study II: Cooling tower fan and gear signatures. Coal-fired power plant.

BPFO BPFI + - 2 x Electrical

+ - 2 x Electrical

Case study II: Cooling tower fan and gear signatures. Coal-fired power plant. Case study II: Cooling tower fan and gear signatures. Coal-fired power plant.

SKF 22310c