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Case Study: Dynamic on line motor analysis

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Case study on HV Induction motor, 6000 V, 8MW

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Case Study: Dynamic on line motor analysis

  1. 1. DYNAMIC ON-LINE MOTOR ANALYSIS TEST Case study on HV Induction motor, 6000 V, 8MW www.koncar-institut.com
  2. 2. DynamicOn-lineMotorAnalysis TEST RESULTSTEST ITEM 02 The latest generation of dynamic on-line motor analysis test doesn’t require for a motor to be stopped. The testing provides comprehensive information on general condition, operation, load, power supply and drive of the motor. HV Induction motor Power [kW] 8000 Current [A] 880 Frequency [Hz] 50 Voltage [V] 6000 cos φ 0,91 Efficiency η [%] 96 Speed [r/min] 994 Synchronous speed [r/min] 1000 Slip [%] 0,6 Rotor bars 112 Stator slots 126 TEST VALUE STATUS CAUTION LEVEL WARN. LEVEL Voltage Level (Over) [%] 98,72 Good 110,00 120,00 Voltage Level (Under) [%] 98,72 Good 95,00 90,00 Voltage Unbalance [%] 0,19 Good 2,00 3,50 THD [% of fund.] 0,24 Good 7,00 9,00 Total Distortion [% of fund.] 0,28 Good 10,00 12,00 Current Level [%] 61,31 Good 110,00 120,00 Current Unbalance [%] 0,14 Good 10,00 20,00 Load [%] 59,79 Good 110,00 125,00 Ef. Service Factor [p.u.] 0,60 Good 1,10 1,25 Rotor Bar [db] -67,68 Good -45,00 -36,00 Op. Point [%] 0,00 Good 20,00 30,00 Loss Difference [%] 0,00 Good 25,00 50,00
  3. 3. DynamicOn-lineMotorAnalysis Voltage Level TestPOWER QUALITY DOMAIN 03 » Voltage Level Test All voltages are around 99% of the nominal value. There is no over/under voltage measured. Voltage Level The test detects presence of overvoltage or undervoltage with regard to rated voltage. The presence of overvoltage stresses the motor insulation, undervoltage can cause current increase above the nominal values.
  4. 4. DynamicOn-lineMotorAnalysis Voltage Level TestPOWER QUALITY DOMAIN 04 Voltage Unbalance Unbalanced voltage condition causes negative sequence currents within the stator, resulting in excessive heat. NEMA derating curve specifies maximum load for each unbalance. » Voltage Unbalance Test Voltage unbalance is under 0,5%. If value above 3.5% is reached, the asymmetry can cause negative sequence currents. This will increase machine losses and additionally heat the machine winding.
  5. 5. Voltage Level Test DynamicOn-lineMotorAnalysis POWER QUALITY DOMAIN 05 Total Harmonics Distortion and Total Distortion Total Harmonic Distortion (THD) and Total Distortion (TD) deal with quantifying the effect of nonfundamental components to the voltage and current waveform. TD values must result in higher values than THD. Both, THD and TD values are low and do not indicate possible machine performance problems.
  6. 6. Voltage Level Test DynamicOn-lineMotorAnalysis 06 » POWER POWER QUALITY DOMAIN » HARMONICS Power quality domain shows the quality level of motor power supply by each phase. Additional harmonic levels increase the losses and machine heating.
  7. 7. DynamicOn-lineMotorAnalysis Voltage Level TestMACHINE PERFORMANCE DOMAIN 07 Effective Service Factor Effective service factor graphically displays the estimated percentage of load derated within the NEMA derating factor. This test identifies how closely the motor is operating to its effective service factor. The test predicts heat- based deterioration. » Effective Service Factor Motor is operating “in green” area, with NEMA derating factor 1.
  8. 8. DynamicOn-lineMotorAnalysis Voltage Level TestMACHINE PERFORMANCE DOMAIN 08 Load and Losses Motor efficiency is calculated from operating load and measured losses (mostly heat). High losses can cause increase of the motor temperature. Motor is operating at high efficiency. Motor Load Measured Losses
  9. 9. DynamicOn-lineMotorAnalysis Voltage Level TestCURRENT DOMAIN 09 Current Level and Current Unbalance The overload of a motor heats the machine and significantly reduces the lifetime of the insulation. It is very important to monitor this regularly. The motor is operating underloaded. There is no current unbalance in this case.
  10. 10. Voltage Level Testd DynamicOn-lineMotorAnalysis 10 SPECTRUM DOMAIN Order n Lower sideband [Hz] Upper sideband [Hz] Hz dB Hz dB 1 49,68 -67,68 50,32 -68,5 2 49,35 -64,1 50,65 -64,1 3 49,03 -75,5 50,97 -71,01 » ROTOR BAR Broken rotor bar sidebands are low (>-60 dB). The values indicate excellent rotor condition. The graph shows stator current spectrum with broken rotor bar sidebands marked. In case when there is a rotor bar damage on a certain frequency, new harmonics will appear showing abnormal values.
  11. 11. Voltage Level Testd DynamicOn-lineMotorAnalysis 11 SPECTRUM DOMAIN Order n Lower sideband [Hz] Upper sideband [Hz] Hz dB Hz dB 1 33,4 -78,39 66,6 -79,17 2 16,9 -81,29 83,1 -79,86 3 0,3 -83,6 99,7 -78,4 » ECCENTRICITY SIDEBANDS Eccentricity sidebands are low. There is no indication of static or dynamic eccentricity. The graph shows stator current spectrum with eccentricity sidebands marked. Here it is important to watch for frequencies and corresponding harmonics that are present because of the static/dynamic eccentricity.
  12. 12. Voltage Level Testd DynamicOn-lineMotorAnalysis 12 SPECTRUM DOMAIN » V/I Spectrum Stator current spectrum with broken rotor bar sidebands marked Stator current spectrum with broken rotor bar sidebands marked. There are no significant sidebands in current spectrum up to 500 Hz. Measurement was taken with 1 kHz for 120 sec.
  13. 13. DynamicOn-lineMotorAnalysis Voltage Level TestTORQUE DOMAIN 13 Torque Ripple Results Motor torque is slightly rippled. There is no indication of serious motor/load problem. Torque ripple should be trended in future. Torque Ripple
  14. 14. DynamicOn-lineMotorAnalysis Voltage Level TestTORQUE DOMAIN 14 Torque Spectrum There are no significant sidebands at critical frequencies in torque spectrum. Typical frequencies are marked. Torque Spectrum
  15. 15. DynamicOn-lineMotorAnalysis Voltage Level TestCONNECTION DOMAIN 15 Supply voltage is sinusoidal and stator currents are slightly rippled. Situation is normal for induction motor operation. Voltage/current phasors are symmetrical and motor (as well as measurement sensors) is properly connected. » WAVEFORMS » PHASORS Voltage – Current waveforms
  16. 16. DynamicOn-lineMotorAnalysis Voltage Level TestCONCLUSION 16 There is no evidence of any faults. The motor is in good condition. The recommendation is to repeat this test in two years. » Induction Motor is in good condition. Supply voltage is symmetrical. There is no over/under voltage » THD and TD values are low. Effective service factor is 1.08 and motor is working with NEMA derating factor 1, with high efficiency » There are no significant sidebands in stator current spectrum. Sidebands for rotor bar faults are low as well as for eccentricity » Motor torque is slightly rippled and it is advised to trend it in time.
  17. 17. CONTACT US TO ARRANGE A VISIT TO YOUR FACILITY Fallerovo šetalište 22, PP 202 Zagreb 10002, Croatia info-iet@koncar-institut.hr KONČAR Electrical Engineering Institute @ +3851 3667-315; 3851 3666-351 www.koncar-institut.com +3851 3667-309 » Hydro plants » Thermal plants » Oil refineries » Cement plants » Sugar production » Off-shore platforms » Paper industry » Steel factories REFERENCES » Fertilizer production » Glass industry » Shipyards » Water management » Water distribution » Pharmaceuticals » Food and beverage » Nuclear plants

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