Siemens Drive Fault Code 7902 !full! -
Begin with verifying that the PLC master is actively exchanging cyclic data with the drive’s configured station address. Then check hardware integrity of the bus cable and termination. If the issue persists, match telegram settings exactly between the drive (P0922) and the master’s hardware configuration.
The variable frequency drive (VFD) tracks electrical behavior to compute mechanical speed. In Vector Control (VC) mode, the Speed Adaptation Controller (SAC) acts as a PID regulator comparing the drive's calculated motor speed profile against the actual speed feedback.
If the system uses closed-loop vector control, a malfunctioning encoder, loose coupling, or damaged feedback cable can report an incorrect speed of "0 RPM" to the drive, tricking it into triggering a stall fault. siemens drive fault code 7902
Regrease bearings if the motor utilizes reloadable grease nipples. 3. Locate the Maintenance Parameters
At its core, Fault 7902 signals a "Motor Stalled" or "Motor Lost Step" condition. On Siemens SINAMICS drives (such as the G120, S120, or G130 series), this fault occurs when the drive detects that the motor has stopped rotating or has significantly deviated from the expected speed, despite the drive actively providing power to rotate it. Begin with verifying that the PLC master is
By following a logical, step-by-step diagnostic process—visual inspection, continuity testing, megger testing, and swap tests—you can pinpoint the cause within an hour. Remember: do not simply reset the fault and restart. Find the physical root cause, or it will return, often with more severe damage (including a burnt motor or drive).
Parameters such as nominal voltage ( p304 ), current ( p305 ), power ( p307 ), or speed ( p311 ) do not match the motor nameplate. Regrease bearings if the motor utilizes reloadable grease
The drive lacks accurate motor data, preventing effective speed/torque calculation.
This draft provides a general overview and might need adjustments based on the specific requirements or details of the Siemens drive model you're working with.
If the drive detects that the measured values deviate radically from the mathematical model expected based on the entered nameplate parameters, or if the current cannot flow correctly, it aborts the test and throws F7902.
Fault 7902 is Siemens' generic term for a loss of motion control. The drive relies on internal models and feedback to ensure the motor's actual speed matches the commanded speed. When a significant discrepancy persists for longer than a preset duration, the drive triggers F7902 as a protective measure to prevent damage to the motor or the driven machinery.
