Output Ph Loss

What does F021 mean?

One or more of the output phases (U, V, W) to the motor has been lost or is significantly unbalanced, if this function is enabled (A557 [Out Phas Loss En]). This condition can lead to severe motor overheating, vibration, and damage if the motor continues to operate on reduced phases.

• Open circuit in one of the motor phases (U, V, or W) due to a broken conductor within the motor cable.
• Loose or corroded connection at the drive output terminals (U, V, W) or within the motor terminal box.
• Internal drive power module (IGBT) failure affecting one specific output phase.
• Damaged motor winding or internal connection creating an open circuit in one phase of the motor.
• Output Phase Loss Enable (A557 [Out Phas Loss En]) activated, and a significant unbalance in output currents is detected.

Click steps to track your progress.

1. 1

   Disconnect the motor from the drive. Measure resistance between each pair of motor phases (U-V, V-W, W-U) at the motor terminal box, ensuring readings are balanced within 5% and match motor data.

2. 2

   With motor cables disconnected from the drive, measure continuity of each output cable conductor (U, V, W) from the drive to the motor end, ensuring no open circuits.

3. 3

   Inspect and tighten all motor cable connections at the drive output terminals (U, V, W) and within the motor terminal box.

4. 4

   If parameter A557 (Out Phas Loss En) is enabled, consider temporarily disabling it to isolate whether the fault is due to detection sensitivity or an actual phase loss.

5. 5

   Visually inspect the drive's output terminals and power modules (if safely accessible) for signs of arcing or component damage.