What it is and where it fits
The Siemens SENTRON 3VA9988-0AB35 is a short-circuit signaling switch designed as an accessory for 3VA1 250/400/630 molded-case circuit breakers. It mounts directly on the breaker to provide remote indication of a short-circuit trip event via changeover contacts (type HQ). The switch is 7 mm wide and 30 mm deep, sized to snap into the accessory slot on the side of the breaker without increasing the panel cutout or DIN-rail footprint. That 7 mm width is the key dimension for fit — it matches the standard accessory slot on 3VA frames.
Contact ratings — what they mean for the circuit
Rated for 0.3 A thermal current (Ith), the switch handles signaling loads, not power. The contact ratings are broken out by duty class: 0.3 A at AC-12 (resistive) and AC-15 (inductive) at both 12 V and 24 V, and 0.1 A at DC-12 at 12 V and 24 V. For DC-13 (solenoid/relay loads) it drops to 0.07 A at 12 V and 24 V. The minimum operating voltage is 24 V DC. Pollution degree 3 and overvoltage category III with a 4 kV surge voltage resistance mean the switch is rated for industrial control panels where conductive dust or humidity is present — not just clean office environments. It can handle transient spikes on the control circuit without failing.
Wiring and termination
Stripped length is 15 mm (0.6 in) for the screw-clamp terminals. The switch provides changeover (CO) contacts — one normally-open and one normally-closed — so it can signal both trip and normal status to a PLC input or alarm annunciator.