Siemens alarm F30003: Power unit: DC link voltage undervoltage
SINAMICS S120 drive fault · SINAMICS S120
What it means
DC link fell below permissible undervoltage threshold.
Likely causes
- line supply dropout or severe sag
- line phase loss
- infeed/pre-charge circuit fault (contactor, resistors)
- blown input fuses
Triage note: Measure all three phases at input terminals first - most cases are supply, not drive.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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input fuses / line contactor per electrical design
line-side protection & contactor · Primary suspect
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6SL3130-… / 6SL3210-…
Line Module (infeed) · Common cause
Need the part urgently?
Send us alarm F30003 with your machine details — typical RFQ turnaround is 24–48h.