What it is and what it does
The Siemens 3RT2025-2DB40 is a SIRIUS power contactor in the S0 frame size, designed for switching motor and resistive loads in industrial control panels. It carries a 24 VDC coil and uses spring-type terminals for the main and auxiliary circuits. Rated for DC-13 duty at 24 V up to 10 A, it handles solenoid and electromagnetic loads common in valve control and brake circuits. At 48 V and 60 V the DC-13 rating drops to 2 A, and at 125 V it is 0.9 A — so for higher-voltage DC switching, check the specific curve. The contactor includes one normally open and one normally closed auxiliary contact as standard, giving basic feedback for PLC input or interlock wiring without an add-on block.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The S0 footprint is 45 mm wide, 102 mm tall, and 107 mm deep — a compact fit for a 24 VDC contactor with spring terminals. Clearance requirements: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so panel layout constraints are minimal. Spring-type terminals accept solid or stranded wire from 1 to 10 mm², with a separate 2x (0.5 to 2.5 mm²) capacity for auxiliary wiring. No screw torque to verify — just strip, insert, and seat.
Operating conditions and switching performance
Rated for operation from -25 °C to +60 °C, with storage from -55 °C to +80 °C. The coil pick-up and drop-out timing is 15 to 18 ms at DC, and arcing time is 10 ms — consistent for a contactor of this class. Maximum switching frequency at AC-1, AC-2, AC-3, and AC-3e duty is 1000 operations per hour; at AC-4 it drops to 300 per hour. Mechanical life is rated at 10 million operations typical, so for high-cycle applications like conveyor indexing, the AC-4 limit is the binding constraint.