Fault 0a7991 | Siemens
The Siemens alarm (commonly appearing on Sinamics drives like the G120 or S120) signifies that Motor Data Identification (Motor ID) is activated
. This is typically not a critical failure but a mandatory safety and performance state where the drive waits for a measurement routine to calibrate itself to the connected motor. Siemens SiePortal Primary Cause and Function
When a drive is first commissioned or its motor parameters are reset, it enters a "standby" mode for identification. Siemens SiePortal The Routine:
The inverter needs to perform a measurement—often at a standstill—which typically involves a "run" command lasting about 10 seconds. During this time, the drive may produce a whistling sound as it identifies stator resistance and other motor characteristics. Automatic Deactivation:
Once the identification run is successfully completed, the alarm should disappear automatically, and the drive transitions into its normal operating state. Siemens SiePortal Troubleshooting and Resolution Strategies
If the alarm persists or prevents operation, technical specialists on the Siemens SiePortal suggest several remedies: Perform the Motor ID Run:
Carry out the standstill measurement by issuing a "run" command. Ensure the configuration is complete and save the settings from RAM to ROM once finished. Manual Inhibition:
If an identification run is not possible (e.g., during a Factory Acceptance Test without the final motor), you can set parameter to inhibit the motor identification feature. Address Communication Blocks:
In some cases, the A07991 alarm appears alongside communication errors like A08526. If the drive is controlled by a PLC, ensure the network connection (Profinet/Profibus) is active and sending the correct control bits. Factory Reset:
If the alarm cannot be cleared through standard parameter changes, performing a factory reset and reconfiguring basic settings may be necessary to clear the drive's internal state. Siemens SiePortal Operational Impact The most significant impact of A07991 is that it typically prevents the drive from starting siemens fault 0a7991
until the identification requirement is satisfied. In industrial transport systems, this can cause "timeout" errors or crashes if the system expects immediate movement while the drive is still in its 10-second calibration phase. Siemens SiePortal Alarms A 7991 and A8526 - SiePortal - Siemens
in Siemens SINAMICS drives (such as the G120 or S120) indicates that Motor Data Identification is activated
. This is an alarm rather than a critical fault, signaling that the drive is prepared to measure motor parameters during the next "Power On" or "Run" command. Meaning & Causes Identification Pending
: The drive is waiting for a run signal to perform a standstill or rotating measurement of the connected motor. Commissioning Mode
: It typically appears during initial setup or after changing motor parameters when the drive needs to "learn" the motor's electrical characteristics. Power Cycle Artifact
: It may reappear after a power loss if the identification process was never completed or if the parameters were not saved to permanent memory (RAM to ROM). Solutions to Clear the Alarm
You can resolve this alarm using one of two primary methods through the Siemens SiePortal Complete the Identification Process
Ensure the motor is safe to run (especially if "Rotating Measurement" is selected). Run command
(via PLC or local control). The drive will energize the motor (often making a whistling sound) for several seconds. The Siemens alarm (commonly appearing on Sinamics drives
Once the measurement finishes, the drive will automatically set parameter p1900 to 0 , and the alarm will vanish.
: Perform a "RAM to ROM" save to ensure the data is kept after the next power cycle. Manually Deactivate the Function
If you do not wish to perform the identification (e.g., during testing with a dummy load), manually set (Inhibited). In some control modes, you may also need to set (V/f control) to bypass advanced motor modeling. step-by-step instructions
for performing a RAM to ROM save on a BOP-2 or via STARTER software? How can resolve the alarm Code 7991 and 8526 - SiePortal
The Siemens A07991 code is not a permanent hardware fault, but rather a warning alarm indicating that the Motor Data Identification (motor tuning) is active. While this is a standard part of the commissioning process for SINAMICS drives like the G120 or G120C, it can be frustrating if it prevents the drive from starting in normal operation. Review of Fault A07991
Usability: This alarm is technically a safety and performance feature. It ensures the drive accurately measures the motor's electrical characteristics (like resistance and inductance) to optimize performance. However, users often find it intrusive when it appears unexpectedly after a power cycle or during site testing where the intended motor isn't yet connected.
Resolution Ease: For experienced technicians, resolving this is straightforward by either completing the identification run or disabling the parameter. For beginners, it can be confusing because the drive will not run normally until this "active" state is cleared.
Performance Impact: Once the identification is successfully completed, the drive's control over the motor is significantly more precise, leading to better energy efficiency and smoother operation. How to Resolve the Alarm There are two primary ways to clear A07991: Complete the Identification:
Ensure the motor is at a standstill and the configuration is complete. Logical address (e.g.
Give the drive a "Run" command. The motor may whistle or hum for about 10 seconds while it measures data.
Once the "tuning" is finished, the drive will automatically set parameter p1900 to 0 and the alarm will disappear.
Crucial Step: Perform a "RAM to ROM" save to ensure the settings are not lost when power is cycled.
Manual Override (Disable):If you cannot run the identification (e.g., during a Factory Acceptance Test without a motor), you can force the alarm to clear by manually changing settings: Set p1900 = 0 (Inhibits Motor ID). Set p1300 = 0 (Switches to V/f standard control mode).
For more technical details or troubleshooting of related codes like A08526, you can consult the official SiePortal Support Forum.
Are you currently commissioning a new drive or did this alarm appear on a system that was already running? How can resolve the alarm Code 7991 and 8526 - SiePortal
1. Meaning (assumption: drive/AC inverter)
- 0A7991 typically indicates a communication or parameter fault (protocol mismatch or corrupted parameter set). Exact meaning varies by product line; consult device-specific fault list when possible.
Step 2: Identify the Affected Module
The diagnostic buffer usually provides:
- Logical address (e.g., 512…527)
- Slot number in the rack
- Station number (for PROFIBUS/PROFINET devices)
Cross-reference this with your hardware configuration to pinpoint exactly which module is reporting the error.
Part 3: Root Causes of Siemens Fault 0A7991
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: