The isn’t a "broken" fault, but rather a digital pause: it means Motor Data Identification is Active . Think of it as your drive asking for a quick introduction to the motor it's about to spin.
: The alarm most often appears when you have triggered a motor identification (p1910) but haven't yet started the motor to let the drive measure its characteristics. Incomplete Configuration
Siemens Fault 0A7991: The Best Guide to Troubleshooting Motor ID Activation
: If you're unable to find the information online, consider contacting Siemens support directly. They can provide detailed information specific to your product and help diagnose the issue. siemens fault 0a7991 best
💡 If your PLC cycle time is too high, consider moving non-critical logic to a different cyclic interrupt (OB) to prioritize the motion control communication. When to Contact Siemens Support
The alarm is triggered when the drive's internal motor model needs to be calculated or updated. The motor is an electromechanical device whose electrical characteristics (like resistance and inductance) can change slightly over time with temperature and use. The drive requires this data to build an accurate mathematical model, ensuring better efficiency, higher torque accuracy, and better protection.
: If the alarm keeps coming back every time you power-cycle, it usually means the parameters weren't permanently saved. Be sure to perform a RAM to ROM save ( P0971 = 1 ). The isn’t a "broken" fault, but rather a
: Completing a basic setup where "Motor ID" was selected. Parameter p1960 : Activating speed controller optimization. How to Resolve Alarm A07991
: No cyclic PROFINET/PROFIBUS communication established. This usually coincides with a bright red Bus Fault (BF) LED on the control unit, meaning the master PLC is not sending valid control words or data over the network. How can resolve the alarm Code 7991 and 8526 - SiePortal
This is typically not a "fault" that indicates a hardware failure, but rather a . It means the drive has been commanded to measure the electrical characteristics of the connected motor (like resistance and inductance) to optimize its control performance. How to Resolve It When to Contact Siemens Support The alarm is
: Usually implies a communication bit (Bit 10) from the PLC is at "0" level, preventing the drive from responding.
A: Yes! The absolute best practice after the identification is complete is to save your parameters . Set P0971 = 1 to copy the settings from the drive's working memory (RAM) to its permanent memory (ROM). This ensures your new settings are kept after a power cycle.
If you see both:
: The motor data identification parameter ( p1900 ) was inadvertently altered during programming. The Three Best Solutions to Clear Alarm A07991 1. Perform a Motor Identification Routine (Recommended)