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

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

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

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) (C) 2006, SUCCESS by DESIGN

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

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 (C) 2006, SUCCESS by DESIGN

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 (C) 2006, SUCCESS by DESIGN

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 (C) 2006, SUCCESS by DESIGN

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

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 Partial Discharge Measurement of capacitive discharges Generally trended on machines over 6kV (C) 2006, SUCCESS by DESIGN

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 (C) 2006, SUCCESS by DESIGN

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

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 (C) 2006, SUCCESS by DESIGN

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

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 (C) 2006, SUCCESS by DESIGN

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 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 (C) 2006, SUCCESS by DESIGN

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% Voltage Distortion Harmonic content of voltage If value too high, rotor and stator heating occurs (C) 2006, SUCCESS by DESIGN

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 Voltage Spikes Monitoring spikes allows the ability to evaluate supply and control conditions (C) 2006, SUCCESS by DESIGN

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