Siemens · SINAMICS G120Fault Code F30003Warning
Siemens SINAMICS G120 — F30003 DC Link Undervoltage
Occurs when the DC-link voltage drops below the lower threshold. Triggered by supply sag, phase loss or capacitor ageing.
Updated: 2026-07-05
Symptoms
- F30003 on power-up or when load applied
- Frequent trips during supply fluctuations
- Sudden stop under load
Probable Causes
- Supply voltage sag
- Input phase loss
- Ageing of DC-link capacitors
- Long/thin supply cable
Checkpoints
- Measure supply voltage under load
- Verify input phases
- Monitor DC-link voltage (r0070)
- Assess capacitor capacitance
Solution
If mains is healthy, aged capacitors collapse the bus under load; the board is repaired by recapping.
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