What it is and where it fits
The Siemens 3VA9988-0AA13 is a SENTRON auxiliary switch — a changeover-contact module that snaps onto 3VA1 and 3VA20 through 3VA25 molded-case circuit breakers. It occupies a 7 mm wide slot on the breaker side, adding remote status indication or control logic without expanding the panel footprint. The 30 mm depth keeps it flush with the breaker body, so no extra enclosure depth is needed.
What the ratings mean for fit
The 0.3 A thermal current (Ith) is the continuous carry rating through the switch contacts — it governs signal-level switching, not power loads. At AC-15 (inductive pilot duty) the contacts handle 0.3 A at both 12 V and 24 V; at DC-13 (solenoid/contact coil loads) they rate 0.07 A at 12 V and 24 V. That means this switch is sized for PLC inputs, contactor coils, or indicator lamps, not motor circuits. The 4 kV surge voltage resistance and overvoltage category III place it in the fixed-installation distribution class — same insulation coordination as the breaker it mounts to.