What it is and what it does
The Siemens SENTRON 3VM9988-0AB12 is a tripped signaling switch — a snap-on accessory for 3VM circuit breakers that reports a trip event via changeover contacts (type HQ). It mounts directly onto the breaker's side, occupying a single 7 mm module width on the DIN rail, and requires no additional wiring to the breaker's trip mechanism. Rated thermal current is 6 A (Ith). Switching capacity varies by duty: at AC-12 (resistive loads) it handles 6 A across 12 V to 240 V; at AC-15 (inductive / solenoid loads) it's rated 3 A across the same voltage range. For DC circuits, DC-12 (resistive) delivers 6 A at 12 V, 4 A at 24 V, 2 A at 48 V; DC-13 (inductive) is 1 A at 12 V, 0.8 A at 24 V, 0.4 A at 48 V, and derates further at 110 V and 250 V. Rated for overvoltage category III, pollution degree 3, and surge voltage resistance of 4 kV — suitable for fixed-installation industrial panels where the signaling contact sees the same environment as the breaker.
Panel fit and integration
Dimensions: 7 mm wide, 30 mm deep, 56 mm high — clips onto the left or right side of a 3VM breaker without expanding the DIN-rail footprint beyond the breaker's own width. Stripped length of 15 mm (0.6 in) for the screw terminals. Designed as an accessory for 3VM circuit breakers. It signals a tripped condition to a PLC or indicator lamp, so the panel builder can wire the changeover contact into the control circuit without running separate sense wires to the breaker terminals.