The Siemens 3VA9978-0BA22 is a SENTRON-series shunt trip (auxiliary release) designed for remote tripping of 3VA4 and 3VA51 through 3VA54, and 3VA61 through 3VA64 molded-case circuit breakers. It operates on a 110-127 V AC supply at 50/60 Hz, drawing a maximum apparent power of 810 VA. This is the component that lets a control system, E-stop circuit, or remote pushbutton open the breaker without an operator at the handle.
The 810 VA inrush at coil pickup is momentary; the holding power is lower, but the control transformer or PLC output driving it must be sized for that peak.
Physical footprint is 21.7 mm wide by 65.1 mm high by 31.2 mm deep — it clips into the accessory slot on the left side of the compatible 3VA breaker frame. The stripped length for the screw terminals is 10 mm (0.4 in). Three slots on the accessory housing accommodate the coil connections and a microswitch for remote status. No DIN-rail space consumed beyond the breaker itself.