What it is and what it does
The Siemens 3RT2025-2BG40 is a SIRIUS power contactor in size S0, designed for switching motor loads and resistive loads in industrial control panels. The 24 VDC coil operates within -25 to +60 °C ambient, and the spring-type terminals accept solid or stranded wire from 1 to 10 mm² — no screwdriver needed for termination, which speeds panel wiring and reduces torque-check time. The DC switching ratings tell you what it can handle on inductive loads: 10 A at 24 V, 2 A at 48 V, 2 A at 60 V, 1 A at 110 V, 0.9 A at 125 V, and 0.3 A at 220 V. At 400 V DC it's rated 3 A. That covers most 24 VDC control circuits and lower-voltage DC motor brake circuits — the 10 A at 24 V is the number to size by for typical PLC-driven contactor coils or solenoid valves.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The 45 mm width (three 17.5 mm modules) fits standard panel layout grids. Clearance: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm at the side — tight enough for dense enclosures but leave the side gap for airflow and tool access. Mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so you can orient it to match cable entry.
Switching frequency and mechanical life
Rated for 1 000 operating cycles per hour in AC-1, AC-2, AC-3, and AC-3e duty. AC-4 drops to 300 cycles/hour — that's the category for plugging and inching, which stresses the contacts harder. Mechanical life is 10 million operations typical, so in normal motor-starting service (AC-3) the contactor will outlast the machine it controls.