The Siemens 3VA9977-0TA20 is a SENTRON COM100 breaker data server — the communication gateway for 3VA molded-case breakers. It mounts in a fixed switchboard inside enclosed rooms (IP20 per IEC 60529) and occupies 5 modular width units on a DIN rail. The unit draws 1.1 A maximum with a 5 W power loss, supplied through screw-type terminals.
Fieldbus and communication
Three protocols on one box: PROFIBUS DP, PROFINET IO, and Modbus RTU. The Ethernet interface runs at 100 Mbit/s (Fast Ethernet) with auto-MDI(X) and a serial gateway for Modbus RTU. Up to 5 active Ethernet connections are supported. The RJ45 port handles twisted-pair cabling.
What it does with the breaker
This server connects directly to one 3VA breaker and reads switch position (On, Off, Tripped) plus exchanges data with the electronic trip unit. It also supplies power to the trip unit. The total daisy-chain length for the breaker communication system is 20 m, with two bus termination connectors and two interfaces on the system bus.
Mounting position is any, but the unit is rated for installation in fixed switchboards inside enclosed rooms only. Operating resource protection class III per IEC 61558.