If you see F07902, your drive has been "orphaned." It thinks the controller (PLC) has abandoned it. 95% of the time, this is a broken cable, a loose connector, or the PLC being stopped.
The Siemens drive fault code 7902 (specifically F07902) indicates that the motor has stalled. This fault occurs when the drive detects that the motor is no longer rotating as expected while under load or during acceleration. Primary Causes
Mechanical Overload: The physical load on the motor is too high, preventing it from reaching the required speed.
Incorrect Motor Data: Motor nameplate parameters (current, power, speed) may be incorrectly entered in the drive configuration.
Missing Identification: Motor data identification and rotating measurements (static optimization) were not performed or completed.
Wiring Issues: Incorrect motor phase lead connections or disconnected motor cables.
Encoder/Sensor Issues: A faulty or incorrectly configured speed sensor/encoder can provide the wrong feedback to the speed controller. Current Limits: The set current limits ( p0640p 0640 siemens drive fault code 7902
) are too low for the application, preventing sufficient torque. Recommended Solutions
According to Siemens Support, you should follow these steps to resolve the fault:
Check Physical Load: Ensure the motor is not physically blocked or overloaded.
Verify Motor Parameters: Double-check the following parameters against the actual motor nameplate: (Rated voltage) (Rated current) (Rated power) (Rated speed)
Perform Motor ID: Rerun the motor data identification at standstill by setting
Activate Flying Restart: If the motor fails to stop after an OFF command before being turned back ON, activate the "Flying Restart" function ( If you see F07902 , your drive has been "orphaned
Adjust Fault Tolerance: If no mechanical issue is found, you can increase the stall detection delay or tolerance in parameters p1745p 1745 p2178p 2178
For detailed technical guidance, you can consult the official SINAMICS G120 Manual or visit the Siemens SiePortal for community-driven troubleshooting. sinamics drive motor fault 7902 - SiePortal - Siemens
To avoid future occurrences of fault code 7902:
When fault 7902 appears, do not simply reset and restart. Follow this systematic diagnostic sequence.
Scenario: A woodworking CNC router with a Siemens Sinamics G120 drive started tripping with F07902 every 20 minutes. The motor was barely warm.
Diagnosis:
Solution:
Lesson: Always cross-reference physical temperature with sensor reading.
Check fault buffer. Often, overcurrent causes rapid heating, which then triggers 7902. Fix the overcurrent first.
This fault indicates that the drive has stopped receiving valid cyclic process data telegrams from the higher-level controller (PLC) within the configured monitoring time.
Once resolved, implement these preventive measures:
Use an infrared thermometer or thermal imager for accuracy. To avoid future occurrences of fault code 7902: