The Siemens SENTRON 3VA9978-0BD13 is a universal auxiliary release designed for the 3VA4, 3VA5, and 3VA6 series of molded-case circuit breakers. This release is intended for remote tripping applications — when the control voltage is applied, the release mechanism triggers the breaker, providing a means to disconnect the load from a central command or safety system.
The 4 kV surge voltage resistance and overvoltage category III mean this release can handle transient overvoltages typical of fixed-installation distribution boards (per IEC 60947-1). The 20 W maximum DC power consumption is the coil's holding power — the release draws this only when energized to keep the trip mechanism ready. In a 24 VDC control loop, that is about 0.83 A; at 48 VDC it is about 0.42 A. The control transformer or power supply feeding the release must be sized to handle this continuous draw across all units in the panel.
At 28.8 mm deep, 25.7 mm wide, and 65.1 mm tall, this release clips into the accessory slot on the side of a 3VA4/5/6 breaker. It occupies one of three available slots, so up to two more accessories (shunt trip, undervoltage release, auxiliary switch) can share the same breaker. The wire stripping length is 10 mm (0.4 in); the terminal accepts AWG18 or 750 mm² conductors. No DIN-rail space is consumed — the release is integrated into the breaker body itself.