The Siemens 3VA9978-0AB13 is a tripped signaling switch — a changeover-contact module that snaps into the right-side accessory slot of a 3VA4, 3VA5, or 3VA6 molded-case circuit breaker. When the breaker trips on overload or short circuit, this switch changes state and sends a signal back to a PLC, alarm lamp, or SCADA input. It takes up one slot, 7 mm wide, on the breaker's side panel. The switch contacts are rated for 0.3 A thermal current; at AC-15 or AC-12 duty on 24 V it switches 0.3 A, and at DC-13 on 24 V it handles 0.07 A — enough to drive a small relay or a PLC digital input, not a motor contactor directly.
Mounting and wiring note
The switch clips into the accessory compartment on the right side of the 3VA breaker frame — no tools needed, no DIN-rail space consumed. It connects via the breaker's internal bus, so no separate power supply is required for the switch itself. The changeover contacts are brought out to screw terminals; strip 15 mm (0.6 in) of wire. The switch occupies one modular slot (7 mm), leaving adjacent slots free for other accessories like shunt trips or undervoltage releases. If the breaker is already in the panel, you can install this accessory without removing the breaker from the DIN rail or the mounting plate.