According to Siemens Technical Support documentation (List Manuals), fault code falls under the umbrella of "Motor blocked" or "Vapor lock" . Depending on the application:
The motor may rotate slightly or emit a humming sound for about 10–60 seconds while it measures stator resistance and inductance.
When dealing with the A07991 notification, keep these best practices in mind: siemens fault 0a7991
The motor may "whistle" or make noise for a few seconds during stationary measurement without rotating.
This method allows the drive to perform the calibration, improving motor control and efficiency. This method allows the drive to perform the
Method 1: Executing the Motor Identification Run (Recommended)
Siemens fault 0A7991 is not a mysterious error to dread—it is a precise diagnostic tool. By understanding that it signals either a mechanical obstruction, a fluid dynamics issue (vapor lock), or a parameter mismatch, you can move from reactive fault-resetting to proactive engineering. Users often see A07991 alongside (No cyclic connection)
Users often see A07991 alongside (No cyclic connection). If A07991 won't clear even after a successful ID run:
: Simply wait for the measurement to complete and the alarm will disappear automatically once the drive is switched to "Ready." F07900 (Drive: Motor locked/speed controller at its limit)
In pumping applications (vertical turbine pumps, centrifugal pumps), 0A7991 often points to or cavitation . The drive attempts to spin the impeller, but gas bubbles in the fluid compress rather than transfer torque. The motor sees no load (low torque, zero speed) – triggering the fault.
If you’ve encountered the alarm or its numerical prefix 0a7991 on a Siemens SINAMICS drive, you’re not alone. This is one of the most common—and frequently misunderstood—warnings faced by engineers during initial commissioning or after a factory reset.