What it is and what it does
The Siemens SIRIUS 3RT1025-3XP00-0GA0 is a power contactor in the S0 frame size, built for switching three-phase motors and resistive loads in industrial control panels. It's rated 11 kW at 690 V AC-3 and 10 kW at 500 V AC-3, so it handles the common 400 V motor lineup up to about 15 kW depending on duty cycle. The AC-4 rating of 15.5 A at 400 V means it's also specced for reversing or inching duty where the contactor makes and breaks stalled-rotor current — not just a run-of-the-mill AC-3 number. Built-in varistor surge suppression means you don't need to add an external RC snubber for basic coil transient protection; the 24 V DC coil holds at 10 A, with a 50 Hz rated voltage of 230 V.
Panel fit and wiring
Mounts on 35 mm DIN rail (DIN EN 50022) with a screw-and-snap-on mechanism — no tools needed for the rail, but the screw terminals on the main circuit need a screwdriver. Side-by-side mounting is allowed, which saves rail space when ganging multiple contactors. S0 frame is 45 mm wide, 119 mm tall, 100 mm deep. Front face is IP20; terminal area is IP00. Main circuit terminals accept 2x (0.25...2.5 mm²) solid or 2x (1...2.5 mm²) stranded, up to 2x 10 mm² max. AWG equivalents: 2x 16-12 solid, 2x 14-10 stranded, or 1x 8. That's enough for the rated currents without needing lug adapters.
Lifecycle and sourcing reality
Built-in varistor variant (3XP00 suffix) is less common than the base 3RT1025. Verify the coil circuit matches. Type 1 coordination requires a 63 A gL/gG fuse upstream; Type 2 coordination needs a 25 A gL/gG fuse. That's the fuse sizing for the main circuit, not the control circuit.