admin
**Question:** We have a 250-ton servo press with Siemens SINAMICS S120. It runs fine for 2-3 hours then trips F30015 (power unit overtemperature) randomly. Resetting works but it comes back. What should I check?
---
**Answer:**
F30015 is a power unit (IGBT module) overtemperature fault. The drive is protecting itself from thermal damage.
## Check the Cooling System First
1. **Check fan operation**: With the drive running, listen for the cooling fans. If silent, the fan has failed. Replacement part: 6SL3162-2BM00-0AA0 (for PM340 modules).
2. **Check air filter**: S120 booksize modules have a filter mat at the bottom inlet. If clogged, airflow drops 50-80%. Clean or replace every 3-6 months.
3. **Check cabinet temperature**: Measure air temperature at the drive inlet. Should be below 40C. If above, cabinet ventilation is insufficient.
4. **Check r0037**: This shows actual heatsink temperature. If it reaches 80-85C before the fault, cooling is marginal. If it trips at 60C, the temperature sensor may be faulty.
## Check the Duty Cycle
F30015 appearing after 2-3 hours suggests thermal accumulation - the drive sustains the load short-term but not continuously.
1. Check r0034 (drive utilization %): if consistently above 90%, the drive is undersized
2. Check production SPM vs. the drive rated continuous current
3. Try reducing SPM by 10% - if the fault disappears, the drive is thermally marginal
## Check for Derating Conditions
The S120 derates continuous current above 40C ambient. At 50C ambient, a 100A module is only rated for ~80A continuous.
If the fault is seasonal (worse in summer), add air conditioning to the electrical cabinet or upgrade to the next size drive module.