What the ratings mean for fit
The 3RT1025-1BW40: Rated coil voltage is 48 VDC. Pick-up voltage is 0.8 x rated value (38.4 V), drop-out is 1.1 x rated value (52.8 V) — so the coil holds in cleanly on a nominal 48 VDC supply and drops out reliably when the supply sags or is switched off. The contactor is size S0, 45 mm wide, 85 mm tall, 101 mm deep, and mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. Side-by-side mounting is allowed, with 6 mm clearance at the side. That means you can pack several S0 contactors on a rail with no extra air gap — useful when panel space is tight. Main contacts are screw-type terminals. Solid wire capacity is 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), max. 2x (0.75...4 mm²); stranded main circuit wire is 2x (1...2.5 mm²), 2x (2.5...6 mm²), max. 2x 10 mm². AWG equivalents: 2x (16...12), 2x (14...10), 1x 8. That covers standard panel wiring up to about 8 AWG — no special crimp tools needed for the main power circuit.
Duty ratings & coordination
AC-3 motor switching at 400 V is rated 7.5 kW; at 690 V it is 11 kW. AC-4 (inching/plugging) at 400 V is 15.5 A. For resistive loads (AC-12) the maximum operating current is 10 A. For DC switching: 24 VDC at 10 A, 60 VDC at 2 A, 110 VDC at 1 A, 220 VDC at 0.3 A. These are the values that determine whether this contactor lives or dies on a given load — match the duty class, not just the voltage. Type 1 coordination requires a gL/gG fuse rated 63 A; Type 2 coordination requires 25 A. Pollution degree 3 (industrial environment). Mechanical life is 10 million operations typical. Coil closing and holding power is 5.4 W DC — a standard 48 VDC power supply can drive several of these without excessive heating.
Panel integration notes
Front face is IP20 (finger-safe), terminal area is IP00 — the wiring compartment is open, so the contactor must be mounted inside an enclosure that provides the overall IP rating. Operating temperature range is -25 to +60 °C; maximum operating altitude is 2 000 m. No instantaneous auxiliary contact is included (0 auxiliary contacts as standard) — if you need a feedback signal for a PLC or a status light, order a separate auxiliary contact block that clips onto the S0 frame.