Siemens alarm F30021: Power unit: earth (ground) fault
SINAMICS S120/G120 drive fault · SINAMICS S120
What it means
Ground-fault monitoring detected leakage current from output phase(s) to protective earth.
Likely causes
- insulation breakdown in motor cable (coolant ingress common)
- motor winding ground fault
- damaged connector strain relief pinching conductors
- power-stage IGBT to heatsink short
Triage note: Megger motor and cable separately at the module terminals to localize before swapping electronics.
Replacement parts
We supply the following units for this alarm — tested, warranty-backed:
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6FX5002-5C…
motor power cable · Primary suspect
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1FK7/1FT6/1PH motor
motor (megger failed) · Common cause
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6SL3120-…
motor module (only if motor & cable test clean) · Check if others ruled out
Need the part urgently?
Send us alarm F30021 with your machine details — typical RFQ turnaround is 24–48h.