Ratings and what they mean for fit
The 3RT1025-1BB40-1AA0: The 24 V DC coil draws 5.4 W during both closing and holding, so the control transformer or DC supply must be sized for that continuous load — no inrush spike beyond the holding power. The main contacts are rated for AC-3 duty at 400 V at 7.5 kW (motor switching) and at 690 V at 11 kW, which covers most three-phase induction motors in the 7.5–11 kW range. For resistive loads (AC-1), the maximum operating current is 10 A at 400 V. For reversing or inching duty (AC-4), the rating is 15.5 A at 400 V — a lower figure than AC-3 because of the increased arcing during plugging. The mechanical life is 10 million operations, so for high-cycle applications like conveyor diverters or pump start/stop, this contactor will outlast the machine's service life. The contactor is rated for pollution degree 3 (industrial environment with conductive pollution), operating ambient -25 to +60 °C, and maximum altitude 2 000 m without derating. The IP20 front protection means it is safe for panel-mount touch protection; the terminals themselves are IP00, so they must be covered by the enclosure or shrouded.
Screw terminals and wiring
The main current circuit uses screw-type terminals accepting 2x (1–2.5 mm²) solid or 2x (2.5–6 mm²) stranded, with a maximum of 2x 10 mm². The auxiliary contacts accept 2x (0.5–1.5 mm²) solid or 2x (0.75–2.5 mm²) stranded. For type 2 coordination (no damage to the contactor under short circuit), the required fuse is gL/gG 25 A; for type 1 coordination (contactor may need replacement), it is 63 A. This matters when designing the branch circuit protection — if you need the contactor to survive a fault, spec the 25 A fuse.
Mounting and integration
The S0 frame is 45 mm wide, 85 mm tall, and 101 mm deep — fits standard 45 mm DIN-rail pitch. Side-by-side mounting is allowed with 6 mm spacing between units for heat dissipation. The screw and snap-on mechanism means no tools are needed for rail installation; a flat-head screwdriver is sufficient for terminal tightening.