Tighten all terminal connections at both the inverter output and the motor terminal box.
Bearings, gearboxes, belts, or driven loads may be mechanically locked or jammed.
If the fault persists under sensorless vector control, execute a new motor identification routine: Set parameter (Identification at standstill). siemens drive fault code 7902
Low-speed, high-torque applications (hoists, mixers, extruders). P1745 is a percentage threshold. The default is 5.0% to 10.0% . If your load causes a larger model error, increase this value.
Siemens SINAMICS drives are the backbone of modern industrial automation, renowned for their precision and robust performance. However, like all complex systems, they occasionally present faults that can bring production lines to a halt. Among the most common and often misunderstood issues encountered by maintenance engineers and automation technicians is . Tighten all terminal connections at both the inverter
: Typically triggers when the motor is already running above the speed threshold. The motor experiences heavy load resistance or a loss of torque control, causing it to fall behind its target speed. Primary Causes of Siemens Fault 7902
| Solution | Action | |----------|--------| | Restart communication | Cycle PLC power or reinitialize bus from master | | Correct telegram mismatch | Set same telegram type (e.g., Standard Telegram 1) in both PLC hardware config and P0922 | | Adjust monitoring time | Increase P2040 to 200–500 ms to avoid nuisance trips | | Re-parameterize drive | Load factory defaults (p0010=30, p0970=1) and reconfigure fieldbus settings | | Replace/repair bus cable | Check continuity, shielding, and termination | If your load causes a larger model error,
Defective speed encoders or loose feedback wiring feed corrupt speed data to the drive.