!!hot!!: Siemens Drive Fault Code 7902

In industrial automation, encountering a Siemens Drive Fault Code 7902—specifically F07902: Motor Stalled—can bring production to a grinding halt. This fault is common across various Siemens Sinamics series, including the G120, S120, and G120XA models. Understanding what this code means and how to systematically troubleshoot it is essential for minimizing downtime. What is Siemens Fault 7902?

2. Fault Description

Fault Code 7902 typically corresponds to:
"PROFIBUS: Cyclic connection failed" (or PROFINET equivalent, depending on the telegram type) siemens drive fault code 7902

How Does the Drive Detect Code 7902?

Siemens drives do not rely solely on external sensors. They use internal current measurement at the inverter’s output stage. When the motor is running, the drive expects balanced currents. If one phase deviates by more than a programmable tolerance (typically set via parameter p3230 in Sinamics), the drive triggers fault 7902. In industrial automation, encountering a Siemens Drive Fault

• P0700 = 6 (fieldbus as command source)
• P0922 → set to correct telegram (e.g., 1, 352, etc.)
• P2040 → increase from default (e.g., 100 ms to 500 ms temporarily for test)
• P8840 = 1 (enable fieldbus interface)

3. Possible causes

• Incorrect motor data entered in parameters (p0300–p0311)
• Speed controller not optimized (p1470, p1472)
• Drive train breakage or load suddenly dropping
• Encoder feedback failure (noisy, loose, or wrong encoder type set)
• Acceleration ramp too aggressive for load (p1120 too short)
• Overspeed threshold (p2162) set too low
• During ramp-down: regenerative energy causes overvoltage → speed overshoot

5. Diagnostics Steps

1. Check LED status on drive:

   Incorrect Motor Data: Motor nameplate parameters (current, power, speed) may be incorrectly entered in the drive configuration. P0700 = 6 (fieldbus as command source) P0922

   Official Siemens Definition (from List Manual):

   • F07902 — Motor overtemperature

     Troubleshooting Steps

     1. Check Physical Connections

     • PROFINET: Inspect the Ethernet cable. Ensure the RJ45 connector is securely "clicked" into the drive's port. Check the link lights on the port; they should be solid or blinking (depending on the drive series, e.g., G120, S120).
     • PROFIBUS: Ensure the cable is firmly connected. Check that termination resistors are switched ON at the first and last devices on the bus line and OFF for devices in the middle.