Siemens alarm A30057: Power unit: Line asymmetry
SINAMICS S120 drive warning · SINAMICS S120
What it means
Frequencies detected on the DC-link voltage suggest line asymmetry or loss of a line phase - alternatively a failing motor phase can produce the same signature. If the condition persists, the drive raises fault F30011 (line phase failure) after at most 5 minutes, depending on unit type. Reducing power delays but does not cure a genuine supply problem.
Likely causes
- unbalanced or single-phasing line supply
- loose line fuse or contactor pole
- motor phase failure reflected onto the DC link
- heavily distorted line voltage from other loads
Triage note: Escalates to F30011 if present continuously; check line phases AND motor feeder connections.
Need the part urgently?
Send us alarm A30057 with your machine details — typical RFQ turnaround is 24–48h.