Motor Phase Failure

What does -OPF mean?

This fault indicates a loss of one or more phases at the output of the drive controller, meaning the motor is not receiving power on all its windings. This can be caused by loose motor connections, a damaged motor cable, or if the drive is significantly oversized for a small motor (making phase loss harder to detect). Operating with a missing motor phase will cause excessive heating and damage to the motor windings and potentially the drive.

• Loose or disconnected motor power cable (U, V, or W) at the drive output terminals (T1, T2, T3) or the motor terminal box.
• Open circuit in one of the motor windings, preventing current flow through that phase.
• Blown output fuse (if installed between the drive and motor for protection, though less common).
• Drive output IGBT failure in one leg, preventing a phase output to the motor.
• Incorrect parameter setting for motor type (e.g., attempting to run a single-phase motor with 3-phase output settings or vice-versa).

Click steps to track your progress.

1. 1

   Disconnect motor cables (U, V, W) from the drive output terminals (T1, T2, T3) before proceeding.

2. 2

   Measure continuity of each motor power cable (U, V, W) from the drive end to the motor terminal using a multimeter.

3. 3

   Measure resistance between motor phases (U-V, V-W, W-U) at the motor terminal box. Expect balanced readings within motor specifications.

4. 4

   Inspect and tighten all motor power connections at both the drive output (T1, T2, T3) and the motor terminal box.

5. 5

   With motor disconnected, attempt to run the drive in V/F mode at low frequency and measure output phase voltages (T1-T2, T2-T3, T3-T1) to check drive output.