What it is and what it does
The Siemens 3RT1025-1AG60 is a SIRIUS power contactor in size S0, rated for motor switching at 7.5 kW in AC-2 duty at 400 V (slip-ring motors, wound-rotor loads) and 15.5 A in AC-4 duty at 400 V (plugging, inching, reversing). The front carries IP20 protection; the terminal area is IP00, so it's meant for enclosure mounting, not open-panel washdown.
Mounting and wiring
Snaps onto 35 mm DIN rail per EN 50022 or screws direct to the panel. Side-by-side mounting is allowed — no gap needed between contactors, which tightens the row on a crowded gland plate. Dimensions: 45 mm wide, 85 mm tall, 91 mm deep. That depth matters when the enclosure back wall is tight against a busway or cable tray. Main terminals accept solid wire up to 2x 4 mm² or stranded up to 2x 10 mm²; auxiliary terminals handle 2x 2.5 mm² solid or 2x 4 mm² stranded. Screw-type terminals on both circuits — no cage-clamp, so torque the screws to the manufacturer's spec on the nameplate.
Coordination and protection
Type 2 coordination (no-weld after fault) calls for a 25 A gL/gG fuse upstream; Type 1 coordination (welding allowed but no fire) needs a 63 A gL/gG fuse. That's the selectivity headroom for a panel designer sizing the branch circuit. Ambient range is -25 to +60 °C — derate above 40 °C per the thermal curve.