The Siemens 3VA9978-0BL33 is a SENTRON shunt trip (auxiliary release) designed for the 3VA4, 3VA5, and 3VA6 molded-case breaker families. It provides remote tripping capability: apply 208–277 V AC (50/60 Hz) or 220–250 V DC to the coil, and the breaker opens — no manual intervention needed. That's the core function for emergency-stop circuits, interlocking schemes, or any panel where you need to kill power from a remote pushbutton or PLC output. The coil draws up to 40 VA apparent power on AC and 35 W active power on DC. The 3-slot design fits the accessory bay on the left side of the 3VA breaker.
This is a snap-on accessory for the 3VA4/5/6 breaker family — it occupies the left-side slot and connects via the breaker's internal bus. No DIN-rail footprint of its own; it rides on the breaker. The stripped length for the coil wiring is 10 mm (0.4 in). Dimensions are 31.2 mm deep, 25.7 mm wide, 65.1 mm high — small enough that it doesn't change the breaker's mounting footprint or the panel fill factor.