Motor Phase Failure

What does OPF mean?

This fault indicates a loss of one or more phases in the connection between the drive controller's output and the motor. This condition can lead to single-phasing of the motor, causing excessive current in the remaining windings and potential motor damage or overheating.

• Loose or corroded connection on one or more motor output terminals (U, V, W) at the drive or motor.
• Broken motor cable conductor or severed connection within the motor terminal box.
• Internal motor winding open circuit (e.g., burned out winding coil).
• Blown output fuse (if present, used for motor short-circuit protection in some systems).
• Faulty internal current sensor on the drive's output side for a specific phase.

Click steps to track your progress.

1. 1

   1. Disconnect motor cables from drive output terminals (U, V, W).

2. 2

   2. Measure resistance between motor windings (U-V, V-W, W-U) at the motor terminal box; values should be balanced and continuous.

3. 3

   3. Check continuity of motor cables from drive end to motor end for each phase (U to U, V to V, W to W) using a multimeter.

4. 4

   4. Inspect all motor output connections (U, V, W) at the drive and the motor terminal box for tightness, arcing, or corrosion.

5. 5

   5. Perform insulation resistance test on motor windings to ground at 500VDC to rule out ground faults.