A30074 alarm in siemens 6RA80 DC Drive indicate that the communication error between the Control Unit and Power Module. This means communications between the Control Unit (CU) and Power Module (PM) via the interface no longer possible. The CU may have been withdrawn or is incorrectly inserted.

1. Reinsert the Control Unit (CU) or the Control Unit adapter (CUAxx) onto the original Power Module and continue operation.
2. If required, carry out a POWER ON for the CU and/or the CUA.