SIRIUS Size S0 power contactor — what the ratings mean for fit
The Siemens 3RT1025-1AU60 is a SIRIUS power contactor in the Size S0 frame, with three normally-open main contacts rated for motor duty. The AC-4 rating of 15.5 A at 400 V is the one that matters for reversing or plugging applications — that's the switching current for starting and stopping a motor under load, where the contacts take the full inrush and arc. For less severe AC-2 duty (starting only, no plugging), it handles 7.5 kW at 400 V. At 690 V it's rated 11 kW, so it covers 690 V line-fed motors up to that power. The coil draws 10 A at 24 V rated value — that's the inrush; the holding current is lower. The contactor snaps onto a 35 mm DIN rail per DIN EN 50022, and the screw-type terminals on the main circuit accept up to 2x 10 mm² or 1x 8 AWG stranded. Front side is IP20, so it's protected against finger contact in the panel; the terminals themselves are IP00, meaning they're live when the panel door is open. Operating temperature range is -25 to +60 °C, and it's rated for pollution degree 3 — that's the typical industrial environment where conductive dust or condensation can occur. The 91 mm depth and 45 mm width mean it fits standard S0 slot spacing on a DIN rail; side-by-side mounting is allowed with no derating down to 6 mm spacing between units.
Coordination and protection — what the fuse ratings tell you
For Type 2 coordination (no damage to the contactor under short circuit), the required upstream fuse is 25 A gL/gG. For Type 1 coordination (contactor may need replacement after a fault), the fuse can be 63 A gL/gG. That's the difference between protecting the contactor itself versus just clearing the fault. In a panel where you want to avoid pulling the contactor after a short, spec the 25 A fuse.
Panel integration notes
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022. The S0 frame width of 45 mm and depth of 91 mm fit standard enclosure layouts. Side-by-side mounting is allowed with 6 mm clearance. Screw terminals accept 0.5 to 4 mm² solid or stranded on the coil side, and up to 10 mm² on the main contacts.