Technicians found no cable breaks. The motor windings tested OK. The clue was the timing – every Monday after weekend shutdown.
This fault indicates that the drive has stopped receiving valid cyclic process data telegrams from the higher-level controller (PLC) within the configured monitoring time.
Elias stopped. He pulled off his safety glasses and wiped the sweat from his forehead. He knew this code. Every drive tech knows the "standard" faults—overvoltage (F0002), overcurrent (F0001)—but the 7-series faults were different. They were communication faults. Ghosts in the machine. siemens drive fault code 7902
Line 4 was the heart of the factory, a massive Siemens-driven servo press responsible for churning out the chassis plates for the new electric vehicle contract. If it was down, the morning shift would start with a disaster, and the plant manager would be breathing down everyone's necks before sunrise.
| 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 | Technicians found no cable breaks
The most common real-world cause is a physical restriction in the driven machinery. A seized bearing, jammed conveyor, blocked pump impeller, or excessive material load can prevent the motor shaft from rotating freely despite the drive supplying maximum current. 2. Incorrect Motor Parameterization
If the motor data identification (p1910 / p1960) was not performed, the internal motor model may be inaccurate. The drive might calculate a speed that does not match reality, leading to a false positive stall alarm. This is especially common when commissioning third-party motors without performing a rotating measurement. This fault indicates that the drive has stopped
Attempting to start a motor that is already spinning without the appropriate "flying restart" function active.
Alternatively, increase the interval limit in if your operational schedule allows for longer intervals between servicing.
Adjust the drive’s dynamics to match the physical load capabilities. Increase Ramp-Up Time ( p1120p 1120
