The Siemens SENTRON 3VA9978-0AB23 is an electrical alarm switch with changeover contacts (type HQ, 7 mm) designed as an accessory for 3VA6 circuit breakers.
Rated for 24 V AC (50 Hz) or 24 V DC operation, with a thermal current limit (Ith) of 0.3 A — that's the continuous current the switch contacts can carry. The switching capacity varies by load type: 0.3 A under AC-12 (resistive) or AC-15 (inductive solenoid) at 12–24 V, and 0.1 A under DC-12 (resistive) at the same voltages. For DC-13 (inductive, e.g. contactor coils), it drops to 0.07 A. So if you're switching a 24 VDC contactor coil, stay under 70 mA or add an interposing relay. Rated impulse withstand voltage of 4 kV and overvoltage category III mean it's suited for fixed industrial installations — the kind of environment where you'd find a 3VA breaker in the first place. Degree of pollution 3 confirms it can handle conductive dust and humidity typical in control cabinets without conformal coating.