Siemens Fault 0a7991 Best -

The drive has the "ID" command but is missing the "ON" command or hardware enables (like STO) to actually pulse the motor.

This is often an Alarm (A) rather than a Fault (F), meaning it’s a warning that the drive is waiting for specific motor identification data, or that a measurement routine is underway.

A: Nothing. The BOP-2 and IOP-2 panels often drop the leading zero, so both codes refer to the exact same condition.

This article provides the , most structured approach to diagnosing and resolving Fault 0A7991. We will move beyond the manual to explore why it happens, how to fix it permanently, and how to optimize your drive parameters to ensure it never returns.

Siemens SINAMICS drives are renowned for their robust performance in industrial automation, but they can occasionally throw complex alarm codes. The (often displayed as Alarm A07991 or A7991 ) is a common issue related to Motor Data Identification activation, particularly in SINAMICS G and S120 series drives. siemens fault 0a7991 best

Parameter P1900 (Motor Data Identification) is set to a value that demands identification on the next run, but the run hasn't occurred. Best Methods to Resolve Siemens 0A7991

If a drive is powered down or undergoes a warm restart while an ID routine is selected but unexecuted, it can throw persistent or repeating alarms.

If your motor was already commissioned and the alarm appears after a power cycle, the drive might be expecting a repeat measurement.

The Siemens drive alarm is a standard status notification indicating that the variable frequency drive (VFD) is prepared to run its auto-tuning sequence to measure electrical characteristics of the connected motor. This code predominantly appears during the commissioning phase of Siemens SINAMICS G120, G120C, G150, and S120 drive families . Because it is categorized as an alarm (A) rather than a hard fault (F), it does not inherently mean the hardware is broken; rather, the drive is intentionally halting normal operations until it can build an accurate mathematical model of the motor. The drive has the "ID" command but is

In the Siemens ecosystem—specifically within the Sinamics S120, G120, and DCM series—Fault A7991 is officially defined as "Motor data identification selected/active."

For the best accuracy, run the motor ID when the motor is at ambient temperature.

If you recently replaced the drive or motor, the parameters might be incorrect.

The motor nameplate data entered into the drive does not align with the physical motor connected. The BOP-2 and IOP-2 panels often drop the

without the actual motor connected, or if you cannot run the identification due to mechanical constraints, you can inhibit the function. Parameter Change (Inhibited).

In many field applications, operators encounter code simultaneously with code A08526 (Profinet No Cyclic Connection) .

At its core, Fault 0A7991 is not a single-point hardware failure code but rather a generic system fault often indicating an "Invalid Parameter Value" or a configuration mismatch within the drive’s memory structure. In many Siemens documentation sets, this fault manifests when the drive attempts to execute a function that relies on data the Control Unit (CU) cannot find or interpret. Unlike an overcurrent fault (which points immediately to the motor or cabling) or an overvoltage fault (pointing to the DC link), Fault 0A7991 is a "sanity check" failure. It signifies that the internal logic of the drive has detected a contradiction between its programmed instructions and the data it is currently processing.

Following Siemens best practices, here are the most effective ways to clear the 0A7991 alarm. 1. Perform a Motor Identification (Active Routine)

Choose (if the load cannot spin) or Rotating (for better accuracy).