When facing an F07902 fault, follow this structured checklist to locate and resolve the issue. Step 1: Perform a Mechanical Inspection
In technical terms, the drive’s internal motor model compares the expected motor speed (based on the setpoint) against the actual speed feedback (or an estimated value). If the deviation between what should be happening and what is happening exceeds a predefined threshold for a set amount of time, the drive shuts down and raises the F7902 fault to prevent damage to the mechanics, the motor, or the drive itself.
If the application requires it, activate flying restart by setting . 6. Perform a Motor ID Run
In the complex world of industrial automation, Siemens drives (ranging from the venerable Masterdrives to the modern Sinamics S120, G120, and S150 families) are known for their robustness. However, like any precision electronic equipment, they occasionally halt production with an error code. Among the more cryptic and frustrating alarms for maintenance technicians is . siemens drive fault code 7902
| Step | Action | Check/Verification Method | | :--- | :--- | :--- | | | Connect STARTER or Startdrive software. Navigate to R0949 . | If Value=2 : Focus on low-speed model (P1745). If Value=1 : Focus on speed encoder/feedback (P1744). | | 2. Visual & Mechanical Check | Manually try to turn the motor shaft (when safe). | Is there resistance? Listen for grinding bearings. Check the holding brake disengages properly. | | 3. Check Wiring | Inspect motor cables at the drive and motor terminals. | Look for loose screws, burnt insulation, or signs of arcing. Ensure all three phases are conducting properly. | | 4. Motor Data Identification | Check if P1900 was performed. | Perform P1910 (static) first. If possible, perform P1960 rotating measurement. This is non-negotiable for SLVC. | | 5. Real-Time Monitoring | Use Trace function in STARTER. Monitor R0063 (speed actual) vs R0062 (speed setpoint). | Is there a large deviation just before the fault trips? Does the current ( R0068 ) hit a limit? | | 6. Adjust Parameters | If no physical problem exists, adjust P2178 , P1745 , or P1744 . | Increase P2178 (delay) slightly. Increase P1745 (tolerance) in 5% increments. |
The Siemens drive fault code F7902 (or 7902) Motor Stalled (or "Motor out of step"). This fault occurs when the drive detects that the motor is not rotating despite a torque or current being applied, or it has lost synchronism with the drive's output frequency. Common Causes Mechanical Overload:
Measure the resistance of the motor windings using a multimeter to ensure balance across all three phases. When facing an F07902 fault, follow this structured
Understanding the root cause is essential for efficient rectifying. The most common triggers include: 1. Mechanical Blockages or Overload
A motor stall fault rarely points to just one component. It can be caused by mechanical failures, incorrect drive parameters, or electrical issues. 1. Mechanical Blockage or Overload
When the drive applies torque but the encoder or back-EMF feedback indicates the rotor is moving below a specific threshold for too long, the system triggers fault 7902. This prevents the motor from overheating due to excessive localized current draw. Primary Causes of Fault 7902 If the application requires it, activate flying restart
Troubleshooting Siemens Drive Fault Code F07902: Causes and Solutions
If you see , 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.
Gather the following before calling: