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Motor Testing (Motor Only)

Motor Testing (Motor Only). Overview. IEEE P1415: “Draft Guide for Induction Machinery Maintenance Testing and Failure Analysis” Key to Understanding Condition-Based Monitoring and Troubleshooting is to understand the capabilities and limitations of testing technology. Overview.

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Motor Testing (Motor Only)

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  1. Motor Testing (Motor Only) (C) 2006, SUCCESS by DESIGN

  2. Overview • IEEE P1415: “Draft Guide for Induction Machinery Maintenance Testing and Failure Analysis” • Key to Understanding Condition-Based Monitoring and Troubleshooting is to understand the capabilities and limitations of testing technology (C) 2006, SUCCESS by DESIGN

  3. Overview • Focus of This Presentation • Stator Winding and Core • Rotor Winding and Core • Vibration and Noise • Bearings and Shafts • Structure and Frame • Ventillation • Accessories (C) 2006, SUCCESS by DESIGN

  4. Condition-Based Technologies • AC High Potential • 2Ev + 1,000V for new • 125-135% of nameplate for existing • Pass/Fail • Acceleration Time • Changes may indicate power supply problems • Trending if conditions are identical • Bearing Insulation • Evaluate for reduced shaft currents • Follow IEEE Std 43-2000 (up for re-affirmation in October, 2005) • Pass/Fail (C) 2006, SUCCESS by DESIGN

  5. Condition-Based Technologies • Bearing Temperature by RTD • Thermocouple or Bulb-Type • Temperature limits vary but generally fall in the range of 90-100C for alarm and 105-120C for shutdown • Higher temp limits for synthetics • Trendable with temp correction • Capacitance • Trended value • Surface contamination, high humidity, high temperature or general insulation breakdown • Effective for trending (C) 2006, SUCCESS by DESIGN

  6. Condition-Based Technologies • Core Loss (Loop Test) • During motor repair to detect inter-laminar insulation damage • No hot spots greater than 10C from ambient core temperature • If value shown: <6 Watts/lb and no change from before and after winding removal • Pass/Fail • Coupling Insulation • Ensure no shaft currents into driven equipment • IEEE Std 43-2000 • Pass/Fail (C) 2006, SUCCESS by DESIGN

  7. Condition-Based Technologies • Current, Demodulation • Used in ESA and MCSA as a method of removing the fundamental frequency from current FFT spectra • Trendable • Current, Running • Indication of load • Pulsating current, measured with an analog probe will indicate rotor faults • Not trendable • Current, Signature Analysis • Provides analysis of electro-mechanical condition and driven equipment condition • Analysis of current FFT spectra • Trendable (C) 2006, SUCCESS by DESIGN

  8. Condition-Based Technologies • Current, Starting • Inrush and starting current is evaluated for anomalies • Trendable • DC High Potential • Trendable when leakage recorded • (2Ev + 1000V) x 1.7 new insulation • Value x 0.65-0.75 for used insulation • A sudden increase in leakage current indicates a fault • Trendable (C) 2006, SUCCESS by DESIGN

  9. Condition-Based Technologies • Dissipation Factor and Power Factor • Utilize AC at the rated voltage of motor • Trended value should not exceed a change of 2% • Grease Analysis • Used to trend and evaluate deterioration of lubrication properties • Trendable • Growler (explain where name from) • Used to evaluate the condition of rotor bars when the rotor is removed from the electric motor • Pass/Fail (C) 2006, SUCCESS by DESIGN

  10. Condition-Based Technologies • Insulation Resistance • Measures insulation value (leakage converted to MegOhms) • IEEE Std 43-2000 • Trendable • Oil Analysis • Used to evaluate the degradation of the lubricating properties of oil • Detect excessive mechanical wear • Trendable • Partial Discharge • Measurement of capacitive discharges • Generally trended on machines over 6kV • Trendable (C) 2006, SUCCESS by DESIGN

  11. Condition-Based Technologies • Phase Angle • The timed measurement between the peak voltage and current at about 7Vac applied to a coil • Compare two coils +/-1 digit from average • Trendable • Phase Balance (Z and L) • Used to detect severe winding unbalances • Detect inter-turn winding contamination • Compare phase to phase patterns between impedance and inductance • Trendable (C) 2006, SUCCESS by DESIGN

  12. Condition-Based Technologies • Polarization Index • Ratio of 10 minute and 1 minute insulation resistance tests • A ratio of 2 or more is required on pre-1970 insulation systems • Trending required on newer insulation • Single-Phase Rotor Test • 10% of motor nameplate voltage applied across one phase of motor • Rotor is turned and current values taken • Variations of 3% or more over 360 degrees of rotation indicate rotor bar fault • Not trendable (C) 2006, SUCCESS by DESIGN

  13. Condition-Based Technologies • Shaft Grounding Current • Measurement of shaft current • Trendable • Shaft Testing • Magnetic particle, liquid penetrant and ultrasonic examination used to evaluate condition of shaft material • Pass/fail • Shaft Voltage • Measurements taken from shaft of motor • Variations may indicate problems with the motor • Trendable (C) 2006, SUCCESS by DESIGN

  14. Condition-Based Technologies • Speed • Uses measurements of motor RPM in order to determine if potential motor or load problems exist • Trendable • Surge Test • High frequency, high voltage impedance-based test to check turn-to-turn dielectric strength • Comparison of waveforms • Not trendable (C) 2006, SUCCESS by DESIGN

  15. Condition-Based Technologies • Surge PD • Variation of the surge test, evaluates partial discharges that result from the high voltage, fast rise-time test • Trendable • Thermography • Utilizes an infrared camera to compare the ambient to test component • Defects can cause a high temperature rise at the point of fault • Trendable (C) 2006, SUCCESS by DESIGN

  16. Condition-Based Technologies • Torque Analysis • Uses three phases of voltage and current in order to calculate torque • Value is displayed and analyzed as torque FFT spectra • Trendable • Ultrasound/Ultrasonics • Used to detect bearing and other electro-mechanical defects in motors • Trendable • Variable Frequency (I/F) • Using about 7Vac, the motor current is measured then applied frequency doubled and the resulting current compared to the first current • Displayed as a percentage, which should be no more than one or two digits from average • Trendable (C) 2006, SUCCESS by DESIGN

  17. Condition-Based Technologies • Vibration • FFT spectra of vibration information is used to trend and detect mechanical and some electrical faults • Trendable • Voltage Unbalance • Voltage measurements detect voltage unbalance defects in supply • Less than 2% recommended, no more than 5% • Trendable • Voltage Distortion • Harmonic content of voltage • If value too high, rotor and stator heating occurs • Trendable (C) 2006, SUCCESS by DESIGN

  18. Condition-Based Technologies • Voltage Drop • Trended measurement of voltage drop when starting a large motor • Changes may indicate defects • Trendable • Voltage Level • Measurements used to ensure that the supply voltage remains +/-10% of nameplate • Trendable • Voltage Spikes • Monitoring spikes allows the ability to evaluate supply and control conditions • Trendable (C) 2006, SUCCESS by DESIGN

  19. Condition-Based Technologies • Winding Resistance • Used to detect broken wires and loose connections. • Trendable unbalance • Winding Temperature • Trended over time in order to determine if overload conditions or insulation failure may occur • Trendable (C) 2006, SUCCESS by DESIGN

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