The Siemens 3VA9978-0AB11 is a SENTRON tripped signaling switch, an accessory designed for 3VA series circuit breakers. It provides a remote indication when the breaker trips, with a thermal current limit (Ith) of 10 A and a stripped length of 15 mm for wiring integration.
The 10 A thermal current (Ith) is the continuous current the switch contacts can carry without exceeding temperature rise limits — it's the hard ceiling for the signaling circuit, not a switching rating. For actual load switching, the ratings break down by duty: AC-12 (resistive loads and solid-state outputs) handles 10 A up to 240 V, while AC-15 (contactor coils, solenoid valves) drops to 6 A at the same voltage. On DC control circuits, DC-13 (switching electromagnets) is the relevant curve: 3 A at 24 V, but only 0.2 A at 110 V — that inductive kick derates fast as voltage climbs.