Disclaimer: This guide applies to SINAMICS firmware versions 4.6 and above. Always refer to the official Siemens List Manual (LH1) for your specific drive unit.
Following Siemens best practices, here are the most effective ways to clear the 0A7991 alarm. 1. Perform a Motor Identification (Active Routine)
. It typically appears during the initial setup or commissioning of Sinamics drives (such as the G120 or S120) and means the drive is waiting to perform a measurement of the motor's electrical characteristics. Siemens SiePortal How to Resolve Fault A07991 siemens fault 0a7991 best
, and the drive is waiting to perform its measurement routine.
When motor parameters have been changed but not yet measured. Best Methods to Clear A07991 1. Perform the Motor Identification Run (Recommended) Disclaimer: This guide applies to SINAMICS firmware versions
Before you start troubleshooting, it's critical to understand that . Rather, it’s an alarm —a notification that the drive is in a specific operational state.
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By understanding and addressing Siemens fault 0A7991, you can ensure the optimal performance and reliability of your Siemens equipment.
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
| Aspect | Detail | |--------|--------| | | 0A7991 | | Display text | "CU: Internal communication error" | | Main cause | EMI, firmware mismatch, CU overload | | Best first fix | Check grounding & shielding | | Best software fix | Increase p2040 or p2079 tolerance | | Criticality | High – drive stops immediately | | Typical affected series | SINAMICS G120, S120, G130, SIMOTION |
If the alarm persists after these steps, check the power cables for insulation issues, as unexpected ground leakage can sometimes interrupt the ID process.