For a motor that has sat in storage or on site without running for a long time, the main risks are a winding that has absorbed moisture and bearing grease that has lost its properties. The catalogue makes an insulation test mandatory before commissioning in this case.

  1. Insulation resistance: measure between winding and frame. If it is low, dry the motor and measure again; do not energise until the value recovers.
  2. Shaft and bearings: turn the shaft by hand a few revolutions. If there is binding, catching or growling, have the bearing inspected before running. On motors with grease nipples, check the condition of the grease.
  3. Terminal box: look for moisture, oxidation or insect nests inside, and check that links and nuts are tight.
  4. Frame and fan: check that the fan cover is not dented, the fan is not broken and the fins are clean.
  5. First run: if possible at no load; watch the three phase currents, the noise and how the temperature develops.

The next steps are the same as for normal commissioning. The longer the idle period, the more important these checks become; for details, see the article on moisture and bearings in long-idle motors.