SIRIUS Size S0 power contactor, 110 V DC coil
The Siemens 3RT1025-3BF40 is a SIRIUS-brand power contactor in the Size S0 frame, rated for a 110 V DC coil. It switches motor loads in control panels, with screw-type terminals for the main current circuit and snap-on mounting onto 35 mm DIN rail per EN 50022. The AC-2 rating at 400 V is 7.5 kW, covering slip-ring motor duty; the AC-4 rating at 400 V is 15.5 A, for reversing or inching applications where the contactor makes and breaks stalled-rotor current. At 690 V the contactor handles 11 kW, and at 500 V it handles 10 kW. The magnet coil draws 5.4 W DC for both closing and holding, so the control transformer or DC supply must be sized for that continuous draw. The contactor is rated for ambient operation from -25 °C to +60 °C, with pollution degree 3 (conductive pollution typical in industrial enclosures).
Mounting and terminal data
Envelope dimensions are 45 mm wide, 85 mm high, 100 mm deep — the depth is the dimension from the DIN rail base to the front of the arc chamber. Side-by-side mounting is permitted with 6 mm clearance at the side; no additional spacing required between contactors on the same rail. Main circuit terminals accept solid or stranded copper: 2x (1 to 2.5 mm²), 2x (2.5 to 6 mm²), or max 2x 10 mm². Auxiliary/control terminals accept 2x (0.25 to 2.5 mm²). AWG equivalents are 2x (16 to 12), 2x (14 to 10), and 1x 8 for the main circuit. Front-face protection is IP20 (finger-safe); the terminal area itself is IP00 (open to touch during wiring). Maximum operating altitude is 2 000 m without derating.
Coordination and auxiliary ratings
For Type 2 coordination (no weld risk after a short circuit), the required upstream fuse is gL/gG 25 A. For Type 1 coordination (contactor may be damaged but no fire risk), the fuse is gL/gG 63 A. Auxiliary contact ratings: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, 6 A at 230 V, 3 A at 400 V. The AC-12 maximum operating current is 10 A. Mechanical endurance is 10 million operating cycles typical. The operating factor range is 0.8 to 1.1 of rated value. No instantaneous contact is fitted.