: Limits for stall detection (such as speed or current thresholds) may be set too strictly for the specific application. Acceleration/Deceleration Rates
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."
Measure winding insulation resistance if required by your site schedule.
The machinery the motor is driving is physically blocked or stuck.
| Root Cause | Solution | |------------|----------| | PLC in STOP | Set PLC to RUN or reconfigure drive to ignore missing telegram ( p2040 = 0 – not recommended for safety) | | p2040 too short | Increase p2040 to at least 2–3× bus cycle time | | Loose connector | Reseat or replace bus connector | | Wrong telegram type | Match p0922 with PLC configuration (e.g., standard telegram 1 for speed control) | | No termination | Activate termination on both ends of PROFIBUS segment | | EMI | Check cable routing, add ferrites, verify shield grounded at both ends | | Faulty option board | Replace communication board (e.g., CBE20 for PROFINET) | siemens drive fault code 7902
Rotate the motor shaft manually to check for smooth rotation.
The drive's motor data (nameplate values) is incorrectly entered in commissioning, leading to poor torque calculations.
Regularly lubricate bearings and check conveyor/gearbox alignments to minimize parasitic friction.
Disconnect the motor cable from the drive terminals (U2, V2, W2). Use a high-quality digital multimeter to measure the phase-to-phase resistance ( ). The resistances must be balanced and equal. : Limits for stall detection (such as speed
Once physical maintenance is complete, reset the internal counter to clear the 7902 code and start a new cycle:
| 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. |
Determines how many seconds a stall must persist before tripping. Motor stall fault tolerance
: If the motor is fine but the load is heavy, you might need to increase the current setpoint (p1610) or the stall delay time (p2178). One common error encountered by automation engineers and
The you are running (Vector control, U/f control, or encoder feedback)
: The motor has run for the maximum number of hours specified in the drive configuration.
In closed-loop control modes, a damaged encoder, loose coupling, or broken feedback cable will feed incorrect speed data back to the inverter.
Subject: G120XA solution to warning F7902 motor out of step - Siemens
The load is too heavy for the motor to start or maintain rotation, causing it to stall. Incorrect Motor Data: