On-li n-line Mot otor or Mon onit itori oring 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: Motor Failure Areas: IEEE Study EPRI Study IEEE Study EPRI Study Bearing Bearing 44% 41% Stator Other Other Stator Rotor Rotor 26% 22% 14% 36% 8% 9%
Motor Failure Causes: Motor Failure Causes: IEEE Study IEEE Study 100% 80% Electrical Fault 60% Mechanical Breakage Insulation Breakdown 40% Overheating 20% 0% Bearing Winding
Safety and Connecting: Low Voltage (Less than 600V) Load Breaker Motor MCC Step one: Running motor Step two: STOP motor Explorer Step three: Connect Explorer Step four: Run and test Step five: STOP motor Step six: Disconnect Explorer
Safety and Connecting: Medium and High Voltage (More than 600V) Load Breaker Motor CTs PTs Step one: Motor is running Step two: Connect Explorer CTs Step three: Connect Explorer PTs Explorer
Acquire Data: Safe, Fast & Easy W/ EP-1 Breaker Motor CTs PTs EP 1 of 700+ EPs at one customer Explorer First Energy RC Pump
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 ect ect. . factor, Harmonic bar chart
Motor Overheating I I 2 R Losses Motor Currents 2 R Losses 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
Motor Condition: Broken Rotorbar Fan 1 hp 1740 rpm
Rotorbar Frequency: slip Synchronous rotor bar freq. f f 1 2 s rotorbar fund . % [RPM] [Hz] RPM RPM 0.1 1798.2 59.88 synch . operat . slip s 0.2 1796.4 59.76 RPM 0.3 1794.6 59.64 synch . 0.4 1792.8 59.52 0.5 1791 59.4 Depends on SLIP! 0.6 1789.2 59.28 0.7 1787.4 59.16 0.8 1785.6 59.04 •Harder to assess with lesser load 0.9 1783.8 58.92 1.0 1782 58.8 •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 signal ' dB down' res .[ dB ] 10 log fundamenta l 42 mA 38 . 5 dB 10 log 300 A
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 54 – 60 dB Excellent Excellent 48 – 54 dB 48 – 54 dB Good condition Good condition 42 – 48 dB 42 – 48 dB Moderate condition Moderate condition 36 – 42 dB 36 – 42 dB Rotor bar crack Rotor bar crack developing or high developing or high resistance joints. resistance joints. 30 – 36 dB 30 – 36 dB multiple cracked / broken multiple cracked / broken bars or end – rings bars or end – rings indicated indicated < 30 < 30 dB multiple cracked / dB multiple cracked / broken bars or broken bars or end-rings very likely end-rings very likely
Current signature: FFT vs. DFLL Need: High Amplitude and Frequency Resolution FFT DFLL Amplitude: 60dB Amplitude: 20dB Resolution: 0.13Hz Resolution: 0.005Hz
Motor Condition: Broken Rotorbar issues • Requires constant torque level • Torque ripple • Next one breaks sooner • Current increases • Temperature increases • Insulation life shortens • Typically non-immediate death
Chain of events: Cause and effect 1. frequency 2. speed Load Motor 3. Torque MCC 4. Power 5. Voltage 6. Current
Calculating Torque: F I I N F : Force F : Current I S : Flux
Calculating Torque: Rotor Current: Monitored with Stator Current T Stator Rotor T(t) = f( V(t), I(t) ) According to Park’s theory, 1920. Flux: Generated by stator Voltage
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. Explorer showed that not all motors run at constant Explorer showed that not all motors run at constant operating condition. The 4 motors at the center display operating 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.
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 operation’s variability.
Case study I: Hydro-mechanical resonance. Brewery. Case study I: Hydro-mechanical resonance. Brewery. Corrective action:
Torque Signature: 4160V submersible pump
Torque Ripple vs. Time # occurrence s 2 frequency 3 . 2 Hz time _ period 0 . 73 s 0 . 11 s
Torque Ripple vs. Time # 2 occurrence s frequency 3 . 2 Hz time _ period 0 . 73 s 0 . 11 s
Torque vs. Frequency: Mechanical Imbalance • Investigating vibration and torque for inaccessible loads:
Comparison of Duct-Mounted Vibration and Instantaneous Comparison of Duct-Mounted Vibration and Instantaneous Airgap Torque Signals for Predictive Maintenance of Vane Axial Airgap Torque Signals for Predictive Maintenance of Vane Axial Fans . Fans . Don Doan Don Doan Don Doan Texas Utilities Texas Utilities Texas Utilities Ernesto Wiedenbrug Ernesto Wiedenbrug Ernesto Wiedenbrug Baker Instrument Company Baker Instrument Company Baker Instrument Company Presented in IEEE CMD / 2005 Presented in IEEE CMD / 2005 Ulsan, Korea Ulsan, Korea
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