Output phase loss

What does 3381 mean?

The drive trips when a motor phase loss is detected. This indicates an interruption in one or more phases supplying power to the motor, which can cause motor overheating, damage, or inefficient operation if not addressed.

• Loose or corroded connection at the drive's output terminals (U, V, W) or the motor's terminal box.
• Break or high resistance in one of the motor power cables (U, V, or W) due to mechanical stress or insulation failure.
• Open winding in the motor itself, resulting in an interruption of current flow through one phase.
• Failure of an output contactor or motor protection switch, specifically one phase remaining open.
• Incorrect installation or wiring of motor filters (e.g., output choke, sine filter) leading to a phase imbalance.

Click steps to track your progress.

1. 1

   1. Power off the drive, disconnect the motor cables (U, V, W) from the drive, and measure the resistance between U-V, V-W, and W-U at the motor side. Readings should be balanced.

2. 2

   2. Perform a continuity test on each individual motor cable (U, V, W) from the drive output terminals to the motor terminal box.

3. 3

   3. Inspect all drive output power terminals and motor input terminals for signs of loosening, burning, or corrosion and re-tighten to specified torque.

4. 4

   4. If an output contactor or motor switch is present, manually operate it and check the continuity across its contacts for each phase.

5. 5

   5. Monitor the drive's output currents (e.g., P1-02, P1-03, P1-04) during a test run (with motor connected) to identify the missing or unbalanced phase.