The Siemens 3VA9978-0AA13 is a SENTRON auxiliary switch — a changeover-contact accessory (type HQ, 7 mm width) designed to snap into 3VA4, 3VA5, and 3VA6 molded-case circuit breakers. It signals breaker position (open/closed/tripped) back to a PLC or status lamp without running separate wires into the breaker arc chamber.
The thermal current (Ith) is 0.3 A — that's the continuous carry capacity through the switch contacts in free air. For switching duty, the part is rated per IEC 60947-5-1: at AC-15 (solenoid/contactor loads) it handles 0.3 A at both 12 V and 24 V; at DC-13 (inductive DC loads like relay coils) it drops to 0.07 A at 24 V. The minimum DC operating voltage is 24 V, so the switch is specified for standard 24 VDC control loops but not for lower-voltage logic (e.g. 5 V or 12 V TTL). Surge voltage resistance is 4 kV, matching the impulse-withstand level expected on 230/400 V distribution panels.