The motor is struggling to turn the mechanical load.
(identification at standstill). This helps the drive calculate the correct control parameters. Check Mechanical Integrity:
This parameter sets the allowable error tolerance for the motor model in percentage (%) . When the error signal ( r1746 ) exceeds the value set in P1745 , the drive flags a stall. Impact: This parameter is active in low-speed operations (below P1755 ). If your application requires high torque at low speeds (e.g., hoisting, extruders), you might need to increase P1745 to allow for minor model inaccuracies.
: The maintenance interval value was set too low during commissioning, causing premature trips. Steps to Troubleshoot and Resolve the Fault
Attempt to rotate the motor shaft manually (if safe and accessible) to ensure the drivetrain moves freely. siemens drive fault code 7902
Ensure the drive knows exactly what motor it is controlling.
When fault 7902 appears, it indicates the drive has detected that the motor is not turning (or turning significantly slower than requested) despite the drive producing torque, often resulting in a shutdown to protect the equipment.
Primarily seen in SINAMICS S120 and G120/G120XA drives using Vector Control (VC) or Sensorless Vector Control (SLVC).
The most common cause is a physical obstruction or an actual mechanical stall in the driven equipment. The motor is struggling to turn the mechanical load
Re-run the motor identification at standstill ( p1900 = 2 ) to ensure the drive has accurate data from the motor's nameplate (p304–p311).
Typically denotes that the identified current loop controller gain is unstable or completely out of range. Check if the motor is significantly oversized or undersized relative to the drive's power rating.
: Motor excitation time (increase if fault occurs immediately at start). p1610p 1610
The drive's motor data (nameplate values) is incorrectly entered in commissioning, leading to poor torque calculations. If your application requires high torque at low speeds (e
Alternatively, increase the interval limit in if your operational schedule allows for longer intervals between servicing.
For persistent cases, Siemens technical support can analyze a drive trace (via Startdrive recording function) to pinpoint whether the fault is load-related or hardware-related. Keep your motor parameters accurate, your cooling vents clean, and your sensor wiring intact—and fault 7902 will become a rare visitor in your maintenance log.
This article provides a comprehensive guide to understanding, diagnosing, and resolving Siemens fault code 7902. What Does Fault 7902 Mean?
Disclaimer: This information is based on standard SINAMICS G120/S120 documentation and community feedback within the Siemens SiePortal .