Cause : Output phase loss comes when motor circuit fault due to missing motor connection, any of the three phases not connected. In scalar control mode, the drive detects fault only when the output frequency is above 10% of the motor nominal frequency.

The 3381 fault code in your ABB ACS560 drive indicates an output phase loss. This means the drive isn't detecting the expected voltage or current on one or more of the motor's output phases. This prevents the drive from controlling the motor properly and can lead to various issues.

1. This is a programmable fault check parameter: 31.19 - Motor phase loss. This fault also comes when you run drive without motor or the rating of motor is small as compare to drive.
2. Connect motor cable.
3. If the drive is in scalar mode and nominal current of the motor is less than 1/6 of the nominal output current of the drive, set parameter 31.19 Motor phase loss to No action.