What are you using (e.g., G120, S120)?
No. It is a “Trip” fault, not a “Fatal” fault. Once the cause is fixed, acknowledge via terminal, bus, or operator panel.
Ensure the drive knows exactly what motor it is controlling.
If the motor isn't genuinely stalling but the drive thinks it is, you can adjust parameters to be less sensitive: Increase delay time: p2178p 2178 (Stall delay). Increase fault tolerance: p1745p 1745 . Specific Fix for G120XA
Check the continuity of the motor cables between the drive output terminals and the motor terminal box. siemens drive fault code 7902
This fault is usually —meaning the drive will not restart automatically. It requires a manual reset after the root cause is fixed.
: The motor has run for the maximum number of hours specified in the drive configuration.
Siemens drive systems are industry standards for precision motor control. However, like all sophisticated automation hardware, they occasionally trigger faults to protect the equipment from catastrophic failure. One common error encountered by automation engineers and maintenance technicians using SINAMICS drives (such as the G120, S120, or V90 series) is , which stands for "Motor stalled."
: Synchronize the Siemens drive maintenance parameters with your facility's Computerized Maintenance Management System (CMMS). What are you using (e
Before changing any settings, ensure the motor can spin freely. Disconnect power to the drive.
Elias shook his head. "It’s an S120 multi-drive system, Marcus. Look at the cabinet. One line supply module, but two motor modules. There’s a main drive for the flywheel, and a secondary servo for the feeder that pushes the metal sheets in. They talk to each other via a telegram to synchronize the speed. If the feeder drive doesn't report its position to the main drive, the main drive locks out to prevent crushing the tooling."
Save the parameters from RAM to ROM to ensure the fault does not return after a power cycle. Preventive Measures for Plant Operations
Regrease bearings if the motor utilizes reloadable grease nipples. 3. Locate the Maintenance Parameters Once the cause is fixed, acknowledge via terminal,
| Step | Action | |------|--------| | 1 | Check (actual speed) — does it really exceed p2162? | | 2 | Verify p1082 (maximum speed) ≥ p2162 (overspeed threshold). | | 3 | Increase p2162 slightly (e.g., 1.1× p1082) if mechanical limits allow. | | 4 | Check encoder: cable shielding, terminal tightness, p0400 encoder type. | | 5 | Perform motor data identification (p1910 = 1) and speed controller optimization (p1960 = 1). | | 6 | Increase deceleration time p1121 to avoid regen overshoot. |
However, a critical nuance often missed: In some Siemens drive firmware versions, can also indicate a wire break or short circuit in the temperature sensor feedback circuit , rather than actual overheating. This dual nature makes it a tricky fault to diagnose without systematic testing.
During commissioning, if the motor nameplate data (current, power, speed, torque) was entered incorrectly, the drive’s internal mathematical model will miscalculate a stall condition.
Siemens Drive Fault Code 7902, while alarming, is a highly solvable problem. By understanding that it is a against stalling, you can systematically diagnose the root cause. Always start with the physical mechanics and wiring, then verify you have performed proper motor identification, and finally, adjust the stall monitoring parameters ( P2178 and P1745 ) to match the specific dynamics of your machine.
