Before attempting a reset, understanding the logic behind the fault is crucial.
Conclusion
Troubleshooting Siemens fault code 0A7991 requires a systematic approach, from understanding the fault and its possible causes to performing detailed checks and applying fixes. By following these steps, technicians and engineers can efficiently resolve the issue, minimizing downtime and ensuring the reliable operation of Siemens equipment.
While there is no official Siemens documentation for a fault code exactly matching "0a7991," the code likely refers to Alarm A7991, which typically indicates that a motor identification (motor ID) has not yet been performed or completed during commissioning. Understanding Alarm A7991
In Siemens SINAMICS drive systems, this alarm serves as a warning that the drive requires data identification to optimize its mathematical model of the connected motor. Until this is performed, the drive may not operate or may operate with reduced performance. Recommended Troubleshooting Steps
To resolve this alarm, users on Siemens SiePortal suggest the following:
Complete the Configuration: Ensure all motor parameters (rated voltage, current, power, speed, etc.) have been correctly entered in the commissioning software. Perform Motor Identification:
Navigate to the commissioning folder in your software (e.g., TIA Portal or STARTER). Select and trigger Motor Identification at standstill.
Give the drive a "Run" command to start the identification process. The motor will not rotate but will be energized with a high-frequency signal to measure its electrical characteristics. siemens fault 0a7991
Save Parameters: Once the identification is complete, perform a RAM to ROM copy to ensure the new parameters are saved permanently to the drive's non-volatile memory. Related Faults to Check
If the code persists or is accompanied by other errors, consider these related Siemens drive faults: F7900: Motor blocked or speed controller at its limits.
F7902: Motor stalled, often due to a lack of static optimization.
A8526: No connection to the PLC/controller, often a communication or configuration issue.
If you are using a specific software like TIA Portal, you can check the full Alarm History by connecting your PC to the drive to view the exact timestamp and detailed description of the event.
Are you currently in the commissioning phase of a new drive, or did this fault appear on a system that was already running?
How can resolve the alarm Code 7991 and 8526 - SiePortal - Siemens
In Siemens SINAMICS drives (such as the G120 series), Alarm A07991 is not a hardware failure but a status message indicating that Motor Data Identification is activated . This occurs when the drive is waiting to perform its "auto-tune" routine to measure the electrical characteristics of the connected motor . Summary of Fault A07991 Before attempting a reset, understanding the logic behind
Meaning: The drive is prepared to perform a motor ID run (static or rotating measurement) upon the next "Start" command .
Behavior: You typically cannot save parameter changes (RAM to ROM) while this alarm is active .
Common Trigger: It often appears during initial commissioning or after changing motor-related parameters . How to Resolve the Alarm
Depending on your current stage of setup, you can either complete the identification or bypass it: Complete the Identification (Recommended) Ensure the motor is safe to run and properly connected .
Give the drive a "Start" or "ON" command via your control source (PLC, BOP, or IOP) .
The motor may emit a whistling sound for several seconds as it carries out measurements at a standstill .
Once finished, the alarm will automatically clear, and parameter p1900 will reset to 0 . Manually Disable the Identification
If you cannot perform the ID run (e.g., during a Factory Acceptance Test without the final motor), you can inhibit the function . While there is no official Siemens documentation for
Set parameter p1900 = 0 to de-activate the identification routine .
In some cases, setting p1300 = 0 (V/f control mode) is also used to bypass complex motor modeling . Finalize the Setup
After the alarm clears, remember to perform a "Copy RAM to ROM" to ensure settings are saved after a power cycle . Community Perspectives
Experts on the Siemens SiePortal Forum often suggest specific sequences for persistent alarms:
“Configure the drive with the basic settings, the drive will do the 'auto tune' at the first 'run' command, wait for that to finish, the motor whistling for a bit and then go quiet. Re make the run command, the fault should go away.” Siemens SiePortal
“If this is a Factory Acceptance Test (FAT), the correct motor may not be available; make P1900 = 0 to inhibit the 'Motor identification'.” Siemens SiePortal
Are you currently performing an initial commissioning, or did this alarm appear suddenly on a drive that was already running? How can resolve the alarm Code 7991 and 8526 - SiePortal
If the fault is intermittent: