Siemens alarm F30074: Communication error between the Control Unit and Power Module
SINAMICS S120 drive fault · SINAMICS S120
What it means
Communication between the Control Unit (CU320/CUA adapter) and the Power Module across their plugging interface is no longer possible. Typical fault values: 0h = CU withdrawn during operation or external 24 V interrupted while the PM was off; 20Ah/20Bh = CU re-inserted on a module with different type code or serial number; 601h = unsupported chassis performance class. The drive remembers which physical module it booted with, so swapping CUs between modules provokes this fault.
Likely causes
- Control Unit/CUA withdrawn or reseated during operation
- external 24 V to CU interrupted while PM unpowered
- CU moved to a different Power Module (serial/type mismatch)
- bent pins or poor seating of the CU/CUA on the module
Triage note: Reinsert the CU/CUA on the original Power Module and POWER ON.
Need the part urgently?
Send us alarm F30074 with your machine details — typical RFQ turnaround is 24–48h.