SIRIUS S0 power contactor with 110 VDC coil
The Siemens 3RT1025-1BF40-1AA0 is a SIRIUS S0-frame power contactor with a 110 VDC magnet coil, screw-type terminals for the main current circuit, and a footprint that fits a 45 mm wide DIN-rail slot. Rated for AC-2 duty at 7.5 kW and AC-4 at 15.5 A, both at 400 V — the AC-2 figure covers slip-ring motor starting, while the AC-4 rating governs plugging and inching cycles where the contactor opens under full load. The coil draws 5.4 W for both closing and holding, so the DC supply needs to sustain that continuously — no drop to a lower hold power on this model.
Mounting and panel integration
Mounts via screw or snap-on onto 35 mm standard rail per DIN EN 50022. Side-by-side mounting is permitted with 6 mm spacing at the side, which keeps the 45 mm pitch per unit in a multi-contactor row. The S0 frame measures 85 mm high by 45 mm wide by 101 mm deep — depth matters when the panel backplate has limited clearance to the enclosure door or rear gland plate. Front face carries IP20 protection; the terminal area is rated IP00, so live parts are exposed once the wiring compartment is open — standard for panel-mounted contactors.
Coordination and short-circuit protection
For Type 2 coordination (no weld risk after a fault) the required upstream fuse is gL/gG 25 A; for Type 1 coordination (device may be damaged but clears the fault) it's gL/gG 63 A. Pollution degree 3 rating means it's suited for industrial atmospheres with conductive contamination. Maximum operating altitude is 2 000 m without derating — above that, the dielectric strength and thermal dissipation need a correction factor.
Auxiliary contact switching capacity
The built-in auxiliary contacts handle 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V — all DC resistive loads. For AC loads at 230 V the rating is 6 A, and at 400 V it's 3 A.