7520 fault in ABB DCS880 drive indicates FBA B communication. This means cyclical communication between PLC and fieldbus adapter module B or between drive and fieldbus adapter module B is lost.

7520 FBA B communication is only activated after the first data set from the overriding control is received by the drive. Before the first data set is received, only A7C2 FBA B communication is active. The reason is to suppress unnecessary faults (the startup of the overriding control is usually slower than the one of the drive).

1. Check the status of the fieldbus communication.
2. Check the settings of group 50 Fieldbus adapter (FBA), 54 FBA B settings, 55 FBA B data in and 56 FBA B data out.
3. Check the cable connections.
4. Check the fieldbus termination.
5. Check the fieldbus adapter.
6. Check that the master is able to communicate.