Electric motors tip: Verify the cleanliness of your test leads

When using test equipment to determine the health and reliability of your electric motors, it is important to also verify the cleanliness of your test leads. Don't allow poor maintenance of your test leads, clips and connectors to reduce the accuracy of the resistance measurement readings. During calibration of the MCE test equipment, PdMA technicians often find test leads with damaged clips or contaminated connectors from everyday usage in industrial environments. Test leads, clips and connectors can be cleaned with an alcohol-based product.

For the phase-to-phase resistance measurement, the advanced 4-wire bridge testing performed by equipment like the MCE offers a reduced concern for test lead connections because the effect of a variable test lead resistance is minimized using the 4-wire design. However, contaminated connectors on test leads used for resistance-to-ground measurements on motors under the test voltage stress of 1,000 to 5,000 volts can be an issue, especially when performing acceptance testing on new or refurbished motors. New and refurbished motors have resistance-to-ground readings in the thousands of Meg or Gigohm range. Some even reach the million Meg or Teraohm range. The MCE provides ranges high enough to measure these values, but to ensure accurate readings of resistance-to-ground at such high levels, perform visual inspections of your test leads and connectors to identify any deficiencies.

For more information on electric motor maintenance, visit the PdMA Corporation Web site at www.pdma.com.