The Siemens SENTRON 3VA9377-0TB50 is a 24 V module accessory designed for the 3VA6 400/600 molded-case circuit breaker family. It provides the control supply and communication interface for the electronic trip unit, drawing a maximum of 0.1 A from the 24 V DC supply with a power loss of 2.4 W.
The module occupies the right switch pocket of the 3VA6 breaker. It has four slots for communication and measurement functions, but note it does not itself communicate with a motor drive, function module, residual current equipment, or the electronic trip unit — it supplies power to the trip unit and provides screw-type terminal inputs for the 24 V DC supply. The 20 % symmetrical tolerance on the control supply voltage means the 24 V rail can sag to 19.2 V or rise to 28.8 V and the module still operates. Safety class III per IEC 61558 means it's a protective extra-low voltage (PELV) device — no earth connection required on the secondary side, which simplifies wiring in the panel.
Dimensions of 63 mm height, 29 mm width, and 33 mm depth mean it fits within the 3VA6 breaker's switch pocket without extending beyond the breaker profile.