Siemens Fault 0a7991 Best -
: Usually implies a communication bit (Bit 10) from the PLC is at "0" level, preventing the drive from responding.
The drive will inject current into the motor (often making a whistling sound) for about 10 seconds to identify its parameters.
A 500ms timer was added to the PLC logic. The "ON" command to the drive was delayed by 1 second after the contactor feedback. Fault 0A7991 never returned. siemens fault 0a7991 best
: Set P1300 = 0 (standard V/f control).
It is common to see alarm A07991 appear simultaneously with fieldbus alarm . This happens when a master PLC is not actively transmitting data to the SINAMICS control unit, leaving the drive locked in an uncommissioned loop. Observed Symptom Underlying Cause Target Remedy A07991 + Active Bus Fault (BF) LED : Usually implies a communication bit (Bit 10)
system moves from commissioning to full production with minimal downtime. Are you experiencing this alarm on a new installation or a system that was previously working Fault A07991 cannot be cleared on SINAMICS G120C drive
In many cases, after the identification is complete or disabled, you must perform a copy (save parameters to non-volatile memory) to ensure the alarm does not return after a power cycle. Common Troubleshooting Scenarios The "ON" command to the drive was delayed
: Motor data identification not performed. This explicitly warns that the VFD lacks crucial operational physics parameters.
For more detailed troubleshooting, you can check the community discussions on the Siemens SiePortal Forum or reference the SINAMICS G120C manual . To give you the most accurate steps, could you tell me: Which are you using (e.g., G120, S120, V20)? Is this a new setup or a drive that was already running ? Dealing with Motor ID ( code 7991 ) - SiePortal - Siemens
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To make your experience with A07991 as efficient and problem-free as possible, follow these expert tips: