Siemens Fault 0a7991 [cracked] May 2026

in Siemens drive systems (such as SINAMICS G120, G130, or S120) is an (not a fatal fault) indicating that Motor Data Identification is active

If torque stays low (<20%) and speed doesn't move, suspect vapor lock (pump) or missing encoder signal. siemens fault 0a7991

High-inertia loads take time to accelerate. The default p2178 (typically 1–2 seconds) is too short. in Siemens drive systems (such as SINAMICS G120,

Prime the pump fully.
Install a pressure switch on suction line to prevent dry starts.
In the drive, activate p0640 (current limit) and use a slower ramp-up (p1120 > 5 seconds) to allow fluid to fill the volute.

To minimize the occurrence of the Siemens fault code 0A7991: Prime the pump fully

Set p2175 warning threshold to 90%. When active, send a PLC message: "Motor near blocked condition – inspect."

Recommendations

Fix: Calculate p2178 = (Load inertia / Motor inertia) × Ramp time × 1.5.
Example: If ramp time is 10 seconds and inertia ratio is 5:1, set p2178 = 25 seconds.

Understanding the Fault Code 0A7991