Siemens Drive Fault Code 7902 Online

| Cause | Explanation | |-------|-------------| | Overload | Motor is consistently operating above its rated torque or current (e.g., conveyor jam, heavy cutting load). | | Insufficient cooling | Blocked cooling fins, failed external fan, or dusty environment reducing heat dissipation. | | High ambient temperature | Motor located near ovens, furnaces, or in non-ventilated enclosures. | | Low speed operation with self-cooling motor | Motors relying on shaft-mounted fans lose cooling at low RPMs but may still draw high current. | | Pulse frequency too high | Higher switching losses in motor iron core generate extra heat; parameter p1800 may be set above recommended value. | | Incorrect motor parameters | Wrong rated current or thermal time constant (p0305, p0611) leads to miscalculated temperature model. |

Fault code: 7902
Typical device family: Siemens SINAMICS / SIMODRIVE (frequency converters and servo drives)
Symptom: Drive reports fault 7902 and trips or blocks operation.
Likely meaning: Encoder feedback error or position feedback failure detected by the drive's encoder interface. The drive cannot reliably determine motor position/speed.
Common causes:

Diagnostic steps (ordered, concise):

Temporary workarounds (use only if safe and permitted):

Preventive measures:

When to escalate to Siemens support or an authorized service partner: siemens drive fault code 7902

Useful information to provide when requesting support:

If you want, I can draft a troubleshooting checklist tailored to a specific Siemens drive model (e.g., SINAMICS G120, S120, or SIMODRIVE) — tell me the exact model and motor/encoder type.

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The Siemens drive fault code 7902 (often displayed as F07902 or A07902 depending on the drive series) typically indicates a motor overspeed condition.

Here is the breakdown and common solutions for this fault. | Cause | Explanation | |-------|-------------| | Overload

If the above points pass but the fault persists, suspect drive hardware:

This fault indicates that the drive has stopped receiving valid cyclic process data telegrams from the higher-level controller (PLC) within the configured monitoring time.

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

| Parameter | Description | Expected value | |-----------|-------------|----------------| | r0035 | Motor temperature (actual) | In °C. If showing -99°C or >250°C, sensor fault is likely. | | p0600 | Temperature sensor type | 0 = none, 1 = KTY84, 2 = PTC, 3 = PT100 | | p0601 | Sensor connection method | 0 = via terminal, 1 = via TM120 module | | p0604 | Overtemperature threshold | Typically 130-160°C for KTY, 90-130°C for PT100 | | p0610 | Motor overtemperature response | Defines reaction (reduce current, trip, etc.) |

Example: If using KTY84, ensure p0600 = 1. Many technicians have accidentally left p0600 = 2 (PTC) – the drive then expects a binary high-resistance signal, not a varying resistance. Diagnostic steps (ordered, concise):

In the drive parameters (using STARTER or Startdrive):

| 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 |

Action:

F07902: Motor overspeed The actual motor speed has exceeded the p2162 (overspeed threshold) value for longer than the time set in p2163.