On-Line Motor Testing
While there are several other tests that may be performed on your motors, the following are offered as a sampling of what is available from Reliability Testing Services, Inc.

Power Quality Snap-Shot

This testing provides a snap-shot of both the circuit integrity and the power quality that is servicing a motor. High resistance connections in breakers, fuses, contactors, motor lug connections, and other locations can cause voltage and current imbalances that are detrimental to motor performance, and if left uncorrected, may result in premature motor failure. Power supply quality may also be a problem, especially in those cases where non-linear loads, variable frequency drives, excessive harmonics, or voltage imbalances exist.

Eccentricity

This test provides a snap-shot of positional relationship between the rotor and the stator as the motor operates under load. If the rotor is not positioned with respect to the stator windings so as to provide a relatively even air gap, asymmetrical magnetic fields can be produced. These imbalanced magnetic fields can cause undesired movement of the stator windings and electrically induced vibration resulting in pre-mature stator winding and bearing failure. Typical causes of this condition include loose or poor bearing / end bell register fits and "soft foot" mounting of the motor. This test offers excellent correlation to vibration analysis.

Cracked rotor bars and bad rotor laminations

Rotor Testing
This test looks for anomalies in the rotor bars, rotor laminations, and the end rings of a squirrel cage induction rotor, and the field coils and windings of synchronous and wound rotor motors. High resistance, porosity, and breaks in rotor bars or end rings of squirrel cage induction rotors can cause excessive start-up currents and higher operating temperatures in a motor. Over a period of time, this can result in more broken bars, and eventually lead to stator damage or heat related failure. Analysis is performed at both the first and fifth harmonic levels.

Off Line Motor Testing

Dirty Stator

Polarization Indexing
This is an off line (de-energized) test for the insulation integrity of a motor stator. Resistances to ground readings are acquired every 5 seconds, and are plotted for diagnostic and trending purposes. This test yields a ratio that is a measure of the motors insulation systems ability to saturate and hold a charge without "leaking" to ground, and is quite often used as an indicator of when a motor needs to be removed from service for a basic cleaning / overhaul cycle. Test voltages are available up to 5000 volts DC.

Test Date 03/06/2004 Test Time 10:47:30 AM Baseline Frequency 1200 Mohm Ph 1 to Gnd Charge Time 30 Voltage 1000 Motor Temp 40 Measured Mohm 280.0 Corrected Mohm 280.0 pF Ph 1 to Gnd 77250

Ohm Ph 1 to 2 0.17050 Ohm Ph 1 to 3 0.16900 Ohm Ph 2 to 3 0.16900 mH Ph 1 to 2 34.690 mH Ph 1 to 3 32.480 mH Ph 2 to 3 35.340 Avg. Inductance 34.170 % Res. Imbalance 0.59 % Ind. Imbalance 4.95 $ Power Loss 39.27 Test Location Motor Leads MCE # 030244

Standard Motor Test
This is an off-line test that yields resistance to ground, capacitance to ground, resistive balancing, and inductive balancing of the motor windings. These are the key indicators of motor health, cleanliness, wetness, and are trendable.