This 3RT1025-1AC00 is a SIRIUS S0 power contactor from Siemens — three normally-open main contacts, a 32 V 50 Hz coil, and screw-type terminals on both the main and auxiliary circuits.
The AC-3 motor-switching rating at 400 V is 7.5 kW, and at 690 V it handles 11 kW — that's the figure that tells you whether this contactor can start and stop a given induction motor under load. Coil is 32 V at 50 Hz, with an operating range of 0.8 to 1.1 times rated voltage — so it pulls in reliably between about 25.6 V and 35.2 V. Below that, don't expect it to hold. The auxiliary contact block carries 10 A at 24 V AC-12, 6 A at 230 V, and derates to 0.3 A at 220 V DC — useful for pilot-duty circuits feeding PLC inputs or indicator lamps. Fuse coordination: for Type 2 (no-weld) protection, use gL/gG 25 A fuses; for Type 1 (allow weld but clear fault), go up to 63 A. That's the spec your panel designer needs for SCCR compliance.
Where it lives in the panel
Footprint is 45 mm wide, 85 mm tall, 91 mm deep — a compact S0 frame that fits standard 35 mm DIN rail. Wire sizes: main terminals accept up to 2x 10 mm² stranded or 1x 8 AWG; control terminals take 2x 0.5 to 4 mm². Screw terminals throughout — no spring-cage here, so torque to the values on the nameplate.