The Siemens 3RT1025-1BE40 is a SIRIUS S0-frame power contactor rated for motor switching up to 11 kW at 690 V AC-3 and 10 kW at 500 V. It carries a 24 V DC coil with a steady holding power draw of 5.4 W. The S0 frame size — 45 mm wide, 85 mm tall, 101 mm deep — makes it a standard fit across motor control centres and panel layouts that use the 35 mm DIN rail per DIN EN 50022. For reversing or plugging duty (AC-4), the rated current drops to 15.5 A at 400 V — the higher switching frequency and inrush on reversal means the contactor derates from its AC-3 capability.
Side-by-side mounting is permitted, which matters when you are packing multiple contactors into a row — the S0 width of 45 mm per unit sets the fill factor. That means the front is touch-safe for panel builders, but the terminals themselves are not finger-safe once the gland plate is open — standard for this class of contactor.
These are the values a panel builder needs to set the branch-circuit protection — oversize the fuse and you lose the coordination the contactor was tested for.
For a BOM that needs this exact S0 contactor with the 24 V DC coil, the part is in standard production and can be specified without concern for imminent phase-out. Sourcing is straightforward for an active Siemens SIRIUS line item. If you hold a panel that originally specified a different S0 contactor — say the 3RT1023-1AL20 — the 3RT1025-1BE40 shares the same S0 frame and DIN-rail footprint, but verify the coil voltage and power ratings match your load before swapping.
Terminal wiring details
Main current circuit terminals are screw-type. They accept solid conductors from 2x 0.5 mm² up to 2x 4 mm², and stranded conductors from 2x 1 mm² up to 2x 10 mm². AWG equivalents run from 2x 16–12 down to 1x 8 for the main contacts. This covers most panel wiring from control-circuit tails to motor-feed cables within the S0 contactor's rating.