or a machine that was already working? I can give you more specific steps to resolve this. Understanding Siemens Drive Fault Codes | XY Automation
: Once the code clears, change parameter p0971 to 1 to copy the data from RAM to ROM . If omitted, the alarm will reappear the next time the system power cycles. How to Deactivate and Bypass Alarm A07991
Test for an undersized motor, which may need to be upgraded to handle the load. If you can share: What type of machine this drive is controlling?
Master Guide: Troubleshooting Siemens Alarm A07991 Best Practices The Siemens Sinamics drive alarm A07991 Go to product viewer dialog for this item. siemens fault 0a7991 best
[p1900 = 2] ➔ [Issue ON Command] ➔ [Wait 15s for Current Injection] ➔ [p1900 Auto-Resets to 0] ➔ [Execute RAM-to-ROM Save] Method B: Disabling the Motor Identification Routine
: Apply an standard ON command (Bit 0 of control word 1 via PLC or local control).
Confirm that the master controller is actively transmitting control word bits. or a machine that was already working
First and foremost, it is crucial to distinguish between a "fault" and an "alarm" in Siemens terminology.
: The drive loses volatile memory settings during a power outage or shutdown because parameters were not saved from RAM to ROM.
If the drive is used in a testing facility (Factory Acceptance Tests) without a physical motor attached, or if operational constraints prevent current injection, you can turn off the routine entirely. Dealing with Motor ID ( code 7991 ) - SiePortal - Siemens If omitted, the alarm will reappear the next
If you are seeing a persistent fault, you can find specific manuals and remedy steps using these resources: SiePortal (formerly Industry Online Support): Siemens Product Support Search to enter the exact code for a PDF manual download. Drive ES/Starter Software: If you have a PC connection, use the Startdrive
This is the #1 cause. For safety, Siemens drives require a (ON/OFF1 command via terminal or fieldbus) before they perform motor identification. If the drive is inhibited, fault 0A7991 appears.
: This often indicates a communication issue between the PLC and the drive. Check your network cables and ensures the PLC is sending the correct control word (bit 10 must be "1" for PLC control).
