Siemens - Fault 0a7991
: Different Siemens families (G120, S120, Simodrive) use slightly different numbering. Error
: Set this to 0 to remove the requirement for motor details entirely during initial testing. Finalize Configuration (RAM to ROM)
To resolve the Siemens fault code 0A7991, users can try the following:
No. It can be a configuration mismatch, network interruption, or even a software issue (missing OB). However, hardware failure is the most common cause after prolonged machine operation. siemens fault 0a7991
If the TIA Portal or STEP 7 project has a module configured (e.g., 16-channel DI) but a physically different module (e.g., 8-channel DI) is plugged in, the CPU will generate Fault 0A7991 during startup or I/O update.
Diagnosing 0A7991 requires a systematic elimination of possibilities. Here are the five most common physical and parametric causes.
: The motor will whistle or hum for roughly 10 to 30 seconds. Do not cancel or disrupt incoming line power. : Different Siemens families (G120, S120, Simodrive) use
If the Basic Commissioning wizard in software like STARTER or TIA Portal had Motor ID selected as a step, the drive will output this alarm once the basic setup is complete.
After analyzing hundreds of field service reports and Siemens support entries (including FAQ entries referencing similar codes), the following are the most frequent triggers for Fault 0A7991:
The notification commonly surfaces under the following scenarios: It can be a configuration mismatch, network interruption,
The drive uses this notification to communicate that a configuration process or a commissioning wizard has primed the VFD to calibrate itself to the physical characteristics of the attached motor. The alarm prevents normal operation because the drive's next action must be tuning, not production. Why the A07991 Alarm Appears
The Siemens alarm code (often searched as 0a7991 or A7991 ) indicates that Motor Data Identification (ID) is activated on a Siemens SINAMICS variable frequency drive (VFD) . Classified as an industrial warning or alarm rather than a terminal drive fault, this alert signals that the control unit is queued up to run a diagnostics routine to analyze and map the electrical properties of the attached motor.
Alarm A07991 is triggered when the VFD's internal firmware expects a motor data identification (Motor ID / Auto-tune) routine to run. This standard automated procedure calculates internal variables like stator resistance, leakage inductance, and magnetic saturation to optimize motor control and efficiency.
