The Siemens SENTRON 3VA9387-0TB50 is a 24 V module designed as an accessory for 3VA2 molded-case circuit breakers in the 400 A, 630 A, and 1000 A frame sizes. It mounts in the right switch pocket of the breaker and provides four slots for communication and measurement functions. The module draws a maximum of 0.1 A from the 24 V supply and dissipates 2.4 W. It powers the electronic trip unit and communicates with the breaker's internal systems, but it does not handle motor-drive, function-module, or residual-current communication, nor does it detect switch position (On/Off/Tripped).
Fit and environment
Physical footprint is 33 mm deep, 29 mm wide, and 63 mm tall. Supply voltage tolerance is ±20 %.