The Siemens Alarm A07991 (often seen in SINAMICS G120/G120C drives) indicates that Motor Data Identification is activated. This is not a "fault" that stops the drive, but rather a warning/status alarm that remains until the identification process is completed or manually deactivated.  Quick Fixes 

During commissioning, the inverter needs to measure the motor's electrical characteristics to ensure it runs efficiently and safely. Until it finishes this "handshake," it won't let the motor start. How to Resolve It

isn't just a code; it’s a warning that the motor identification hasn't been completed. To the plant manager screaming over the radio, it was a million-dollar hour of lost productivity. To , it was a puzzle.

By following these best practices and guidelines, users can minimize the risk of encountering the Siemens fault 0A7991 and ensure optimal device performance.

If you are commissioning a new motor, you should allow the drive to complete its measurement. Action: Issue a "Power On" or "Run" command to the drive.

Factory Reset: If the drive is stuck and the alarm won't clear, try a factory reset and re-enter basic motor settings before attempting the "Run" command again.