If using an encoder, incorrect wiring or scaling can cause the drive to think the motor is not moving. Step-by-Step Troubleshooting Guide Follow these steps to diagnose and clear the 7902 fault. Step 1: Check the Mechanical System
For SINAMICS G120XA drives experiencing frequent 7902 faults, Siemens recommends the following:
Fault 7902 ("Motor Stalled") means that the speed controller has reached its maximum capability, yet the actual speed of the motor does not match the setpoint. Essentially, the drive thinks the motor is "stalled" or blocked.
"Fault 7902," Elias muttered, typing his password into the Siemens TIA Portal software on his laptop. "Communication fault. Drive-to-Drive data exchange failure."
To resolve Fault F7902 efficiently, technician teams should follow a structured, step-by-step diagnostic workflow. 1. Audit the Motor Nameplate Parameters siemens drive fault code 7902
[F07902 Motor Stalled Fault] │ ┌────────────────┼────────────────┐ ▼ ▼ ▼ Mechanical Electrical Software & Obstructions Failures Parameters ├─ Jammed load ├─ Bad phases ├─ Missing Motor ID ├─ Seized brg ├─ Brake issue ├─ Low current limits └─ Overload └─ Loose wire └─ Strict tolerances 1. Mechanical Jamming and Overload
The Siemens drive fault 7902 is effectively a "Motor Stalled" protection mechanism. In almost all cases, will resolve the issue. If the error persists, check mechanical components for blockage.
As if on cue, the breakroom lights flickered. The deep, vibrating thrum of the plant’s ventilation system shuddered and died. A moment later, the emergency lights kicked in, bathing the hallway in an eerie, sterile red.
Ensure the drive is operating in an environment that meets Siemens’ specified conditions. Check for adequate ventilation and that the ambient temperature is within recommended limits. If using an encoder, incorrect wiring or scaling
If the deviation between the actual speed and the expected setpoint breaks the default stall window threshold—and remains there longer than the stall delay time configured in parameter —the processor determines the rotor is no longer keeping pace with the magnetic field. The drive trips on F07902 to protect the winding insulation from thermal destruction. Key Parameter Impact on Fault 7902 p2178 Motor stalled delay time
Fault code 7902 in Siemens drives typically indicates a specific issue related to the drive's operation. The exact meaning can vary slightly depending on the specific model and version of the Siemens drive. However, generally, this code points to a problem that requires attention to prevent further issues or damage to the drive and connected equipment.
If the system uses closed-loop vector control, a malfunctioning encoder, loose coupling, or damaged feedback cable can report an incorrect speed of "0 RPM" to the drive, tricking it into triggering a stall fault.
Primarily seen in SINAMICS S120 and G120/G120XA drives using Vector Control (VC) or Sensorless Vector Control (SLVC). Essentially, the drive thinks the motor is "stalled"
Inspect gearboxes, belts, and couplings for visible damage or misalignment. Step 2: Verify Motor Parameterization
If the motor features an integrated mechanical brake, the brake may not be releasing properly due to wiring faults or actuator failure. 2. Incorrect Drive Parameterization
For persistent cases, Siemens technical support can analyze a drive trace (via Startdrive recording function) to pinpoint whether the fault is load-related or hardware-related. Keep your motor parameters accurate, your cooling vents clean, and your sensor wiring intact—and fault 7902 will become a rare visitor in your maintenance log.