Siemens Drive Fault Code 7902 (720p — HD)

Ensure that the wiring matches the voltage levels supplied by the drive. For example, a 230V/400V motor must be wired in Delta for a 230V drive output, and Star for a 400V drive output.

: Inspect the connected machinery for jams, broken bearings, or excessive friction that could be stalling the shaft. Adjust Stall Protection Parameters

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 you are staring at a panel displaying “F07902” or “Fault 7902,” you know production has stopped. This article provides a deep dive into what this fault means, why it occurs, and—most importantly—a step-by-step guide to getting your machinery back online. siemens drive fault code 7902

Ensure no mechanical binding or seized bearings are preventing rotation.

The most straightforward reason is a heavy mechanical load that exceeds the torque capacity of the motor or drive combination. If a mechanical brake does not release properly, or if downstream equipment (such as conveyors, pumps, or mixers) is jammed, the motor will lag behind its frequency command. 2. Missing or Incomplete Motor Commissioning

While these codes sound identical, they describe two distinct operational scenarios: Ensure that the wiring matches the voltage levels

Acceleration times that are too short cause the drive to hit torque limits prematurely. 3. Electrical and Feedback Issues

If using an encoder, monitor the actual speed value ( r0061 or r0063 ) against the setpoint speed during the brief moments before the drive trips. If the motor is physically spinning but the drive reads 0 RPM, check the encoder wiring, power supply, and shielding. Step 5: Run Motor Identification (ID)

Parameters governing the maximum current limit (p0640) or torque limits (p1520/p1521) might be set too low, preventing the motor from drawing enough power to overcome normal starting inertia. Adjust Stall Protection Parameters In hoisting or vertical

If the drive hasn't performed a proper "Motor ID" or "Stationary Measurement" (parameter p1900 ), it may have incorrect data for the motor’s electrical characteristics, leading to false stall detections.

Once physical maintenance is complete, reset the internal counter to clear the 7902 code and start a new cycle:

| Parameter | Description | Typical Value | |-----------|-------------|----------------| | p2040 | Monitoring time for telegrams (ms) | 100–500 ms | | p0922 | Telegram configuration (e.g., 1, 352, 999) | Match PLC configuration | | r2060 | Telegram received? | Should increment cyclically | | p8700 (PROFIBUS) / p8839 (PROFINET) | Station address / device name | Unique and matching PLC |

Follow this structured matrix to diagnose and clear the 7902 fault code systematically.