The Siemens SENTRON 3VA9978-0BL10 is a shunt trip (auxiliary release) accessory designed specifically for the 3VA4, 3VA5, and 3VA6 molded-case circuit breaker families. It operates on a 12V DC control signal, drawing up to 30 W at maximum load. When energized, it mechanically trips the breaker — used for remote emergency-off, undervoltage protection schemes, or interlocking between feeders.
It can handle transient spikes on the line side of the breaker without flashover. The 30 W power draw is the peak inrush when the solenoid fires; steady-state coil holding current is lower, but the control transformer or PLC output driving it must be rated for that peak. Physical fit: 31.2 mm deep, 25.7 mm wide, 65.1 mm tall. The width is a single modular unit (1 MW), so it clips into the same DIN-rail slot as a standard miniature breaker. The 10 mm stripped length on the flying leads matches standard ferrule and terminal-block practice.
The shunt trip mounts inside the 3VA breaker's accessory slot — no additional DIN space consumed. The three accessory slots on the 3VA frame mean you can stack this with an auxiliary switch or alarm contact in the same breaker. Wire the 12V DC control circuit with a free-wheel diode across the coil if the driving relay is solid-state; the inductive kick at dropout can exceed 4 kV on a long cable run.