Siemens - Drive Fault Code 7902 Work

In some applications, immediate trip on overtemperature is too aggressive. You can modify the response:

: Ensure the motor is not physically blocked or overloaded.

A magnetic contactor between the drive and motor had a pitted auxiliary contact that overheated slightly on the first start of the week, dropping one phase for 50ms. As the day progressed, thermal expansion improved contact – until the next Monday.

Check fault buffer. Often, overcurrent causes rapid heating, which then triggers 7902. Fix the overcurrent first. siemens drive fault code 7902

Understanding the internal detection mechanisms, distinguishing it from related codes, and knowing how to adjust parameters systematically can help isolate and fix the root causes of an F07902 fault. The Technical Mechanics Behind Fault 7902

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.

Set (Motor data identification at standstill/Static Optimization). In some applications, immediate trip on overtemperature is

[F07902 Motor Stalled Fault] │ ┌────────────────┼────────────────┐ ▼ ▼ ▼ Mechanical Electrical Software & Obstructions Failures Parameters ├─ Jammed load ├─ Bad phases ├─ Missing Motor ID ├─ Seized brg ├─ Brake issue ├─ Low current limits └─ Overload └─ Loose wire └─ Strict tolerances 1. Mechanical Jamming and Overload

Before altering any electronic parameters, rule out mechanical failure. Safely lock out and tag out (LOTO) the drive system.

| Step | Action | Check/Verification Method | | :--- | :--- | :--- | | | Connect STARTER or Startdrive software. Navigate to R0949 . | If Value=2 : Focus on low-speed model (P1745). If Value=1 : Focus on speed encoder/feedback (P1744). | | 2. Visual & Mechanical Check | Manually try to turn the motor shaft (when safe). | Is there resistance? Listen for grinding bearings. Check the holding brake disengages properly. | | 3. Check Wiring | Inspect motor cables at the drive and motor terminals. | Look for loose screws, burnt insulation, or signs of arcing. Ensure all three phases are conducting properly. | | 4. Motor Data Identification | Check if P1900 was performed. | Perform P1910 (static) first. If possible, perform P1960 rotating measurement. This is non-negotiable for SLVC. | | 5. Real-Time Monitoring | Use Trace function in STARTER. Monitor R0063 (speed actual) vs R0062 (speed setpoint). | Is there a large deviation just before the fault trips? Does the current ( R0068 ) hit a limit? | | 6. Adjust Parameters | If no physical problem exists, adjust P2178 , P1745 , or P1744 . | Increase P2178 (delay) slightly. Increase P1745 (tolerance) in 5% increments. | As the day progressed, thermal expansion improved contact

Motor cables (U, V, W) are connected improperly, or the encoder signal is reversed (if applicable). Premature Startup: Motor excitation time ( p0346p 0346

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.

Use a digital multimeter and, if available, a megohmmeter.

Connect via STARTER (for older drives) or Startdrive in TIA Portal. Check: