Siemens Fault 0a7991 -

Unlike critical system faults that permanently trip the drive to prevent damage, the "0A7991" status acts as a safeguard. It signals that the drive is primed and waiting to measure the physical and electrical characteristics of the attached motor. The drive needs this information to build an accurate mathematical profile to optimize torque, efficiency, and safety over the life of the machine. Why is Alarm A07991 Triggered?

: The drive is waiting for a run signal to perform a standstill or rotating measurement of the connected motor. Commissioning Mode

The Siemens fault code (often searched as 0a7991 ) specifically indicates that Motor Data Identification is activated . This is not a critical equipment failure but rather a status alarm triggered during the commissioning or configuration phase of Siemens SINAMICS drives , such as the G120, G120C, and G150 series. Understanding Alarm A07991

. This is typically not a critical failure but a mandatory safety and performance state where the drive waits for a measurement routine to calibrate itself to the connected motor. Siemens SiePortal Primary Cause and Function siemens fault 0a7991

If vector control is selected as the operating mode, deactivating the identification without performing it may cause alarm A07994 to appear instead. This is the drive’s way of warning that accurate motor modeling is absent, which can lead to reduced performance and stability.

For any permanent or recurring issue, official Siemens Technical Support remains the most reliable resource. Many discussions about this alarm can also be found in the portal, where a thriving community of engineers and Siemens experts share field-tested solutions.

Depending on your current stage of setup, you can either complete the identification or bypass it: Ensure the motor is safe to run and properly connected . Unlike critical system faults that permanently trip the

: This turns off the motor data identification and rotation test.

By following these recommendations, users can reduce the likelihood of encountering this fault code and ensure optimal performance of their Siemens equipment or systems.

Navigate directly to the drive parameters using your control panel or TIA Portal. Why is Alarm A07991 Triggered

If the PLC is not connected, set p2030 to 0 (Disable fieldbus).

After the alarm vanishes, execute a RAM to ROM copy operation (e.g., set P0971=1 ) to ensure the newly identified motor data is stored permanently, surviving a power cycle.

Solving the A7991 alarm typically follows two logical branches: completing the identification (recommended) or temporarily deactivating it.

You have inputted standard motor nameplate data (voltage, current, power) and the drive automatically schedules a standstill or rotating optimization for the next power-on/run command.

This method allows the drive to perform the calibration, improving motor control and efficiency.