This fault is specific to , G120C , G120P , S120 , and V20 drive families when using Encoderless Vector Control or Servo control. Deep Report: Siemens Fault 0.A7991 1. Executive Summary | Attribute | Details | | :--- | :--- | | Fault Code | 0.A7991 (A07991 / F07991) | | Full Text | Motor blocked / Motor locked | | Drive Series | SINAMICS G120, S120, G120C, G120P, V20 | | Default Reaction | OFF2 (Coast to stop) | | Fault Class | 7 (Mechanical malfunction) | | Severity | High (requires reset) | 2. Technical Description Fault 0.A7991 is triggered when the drive detects that the motor shaft has stopped rotating despite the inverter applying sufficient torque to accelerate it. It indicates a discrepancy between the setpoint speed and the actual speed (or estimated speed) over a defined monitoring time.