Before changing any electronic parameters, isolate the power and verify the mechanical health of the system.
: 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
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. siemens drive fault code 7902
Always opt for a Stationary Measurement (p1910 = 1) before attempting a rotating measurement. The stationary measurement is safer and acts as an excellent gatekeeper for finding basic wiring faults.
If the mechanics are fine and the motor simply takes longer to accelerate due to high inertia, you may need to desensitize the stall detection logic. Before changing any electronic parameters, isolate the power
Follow this structured matrix to diagnose and clear the 7902 fault code systematically.
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 Primary Causes of Siemens Fault 7902 Disconnect the
The threshold speed for stall detection (p2175) or the stall delay time (p2177) may be configured too aggressively for the specific application. 3. Motor and Control Mode Mismatches
Tell me the exact Siemens drive model (e.g., SINAMICS G120 CU240E-2 ) and whether you have an encoder or are running in V/f or vector control.
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.
: Ensure your motor parameters (p304–p311) match the nameplate exactly.