What it is and what it does
The Siemens 3RT1025-1AL24-ZW98 is a 3-pole contactor from the SIRIUS series, rated for AC-3 duty at 7.5 kW at 400 V with a 230 V AC coil. That AC-3 rating means it's designed for starting and stopping squirrel-cage motors — the most common motor load in industrial panels — and the 7.5 kW figure at 400 V covers a standard 10 HP motor at 480 V, with the 50/60 Hz coil making it line-voltage agnostic across common power grids. The size S0 frame keeps the panel footprint compact for this current class.
What the auxiliary contact count means for your circuit
The 2 NO + 2 NC auxiliary contacts are built into the contactor, not as a separate block. That's enough for a basic motor starter: one NO for the seal-in (holding contact), one NO for a run-status signal to the PLC, and the two NC contacts for feedback from the overload relay or a safety circuit. If your design needs more, you'll add a 3RT19 series auxiliary contact block on the side — the S0 frame accepts one.
Panel integration note
Snap-on DIN rail mounting to EN 60715, size S0. Screw terminals accept 1.5 to 6 mm² solid or stranded — strip length 10 mm, torque to 1.2 Nm. The multiunit packing of 6 means you get one part number for a batch build, which simplifies kitting for a panel shop running multiple starters.