When fault 7902 appears, do not simply reset and restart. Follow this systematic diagnostic sequence.
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.
What (e.g., G120, S120) are you working with?
However, a critical nuance often missed: In some Siemens drive firmware versions, can also indicate a wire break or short circuit in the temperature sensor feedback circuit , rather than actual overheating. This dual nature makes it a tricky fault to diagnose without systematic testing. siemens drive fault code 7902
To minimize the reoccurrence of F07902 in your facility, implement these proactive measures:
Siemens Drive Fault Code 7902: Comprehensive Troubleshooting Guide
The drive lacks accurate motor data, preventing effective speed/torque calculation. When fault 7902 appears, do not simply reset and restart
→ infinite ohms → fault 7902. Short circuit → near 0Ω → fault 7902.
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Indicates a problem during the stationary measurement of the stator resistance or leakage inductance. This strongly points toward wrong nameplate data or an open circuit/contactor problem on the specific output phases. Use a high-quality digital multimeter to measure the
) at standstill to allow the drive to precisely measure stator resistance and leakage inductance. Step 3: Optimize Acceleration and Limit Parameters
The drive triggers this fault when the deviation between the calculated motor speed and the actual speed exceeds a specific threshold for a set amount of time. sinamics drive motor fault 7902 - SiePortal - Siemens