This comprehensive guide breaks down why this fault happens across major Siemens SINAMICS variable frequency drives (VFDs)—including the —and provides an actionable, step-by-step troubleshooting protocol. Anatomy of Fault F07902
In hoisting or vertical axis applications, a mechanical holding brake is often used. If the brake fails to release (due to a blown rectifier or sticky mechanism), the drive attempts to move against a locked brake, resulting in an immediate 7902 fault.
If the fault consistently happens during startup or at very low frequencies in sensorless vector control:
Once the drive registers that the motor has stalled, it does not shut down immediately. It waits for the duration defined in (Motor Stalled Delay). If the condition persists for that entire period, the drive outputs Fault 7902 and trips. siemens drive fault code 7902
Bearings failure, broken drive components, or a faulty gearbox.
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Based on Siemens technical support forums and real-world case studies, the F07902 fault rarely has a single cause. It typically falls into one of the following categories: This comprehensive guide breaks down why this fault
If a process cannot be interrupted, F7902 can be temporarily suppressed by changing its response type. This is a temporary workaround, not a solution, and should be used with extreme caution.
While these codes sound identical, they describe two distinct operational scenarios:
The load inertia is higher than what the motor was designed for, causing it to stall during acceleration. 2. Parameterization and Commissioning Issues If the fault consistently happens during startup or
The actual or estimated motor speed remains below the stall speed threshold ( p2175p 2175
If you must run a rotating identification ( p1910 = 2 ), uncouple the motor from the gearbox or mechanical load if possible. High load inertia or static friction during a tuning cycle will cause the identification algorithm to fail, generating an F7902 error.
Drive trips during acceleration or while running at low speeds. The motor hums or vibrates but does not spin. Sudden trip upon startup. Causes of Siemens Fault 7902
In the drive parameters (using STARTER or Startdrive):
The fault is most relevant in , where the drive requires precise motor modeling. In V/f control (a simpler method), the drive does not typically monitor for this condition, which is why switching to V/f mode can sometimes mask the issue.