The Siemens SIRIUS 3RT2025-1BA40 is a Size S0 power contactor built for switching motor loads in control panels. It mounts on 35 mm DIN rail per EN 60715 via screw or snap-on fastening, so it integrates into standard panel layouts without adapter plates.
What the ratings mean for fit
The 24 VDC coil pulls in at 0.8 of rated voltage (about 19.2 V) and drops out with a 15–18 ms delay, which is fast enough for most interlocking circuits but not a safety-rated instant drop. The main contacts are rated for AC-1 resistive loads up to the contactor's full thermal current and AC-3 motor switching at 400 V at 3 A — that's roughly a 1.1 kW motor at 400 V three-phase. AC-4 (inching/jogging) is limited to 300 operations per hour versus 1 000 for AC-3, so if your application cycles the contactor under load repeatedly, this part is not the right choice; you'd want a higher-rated frame or a dedicated reversing pair. Wire range accepts 1–10 mm² solid or stranded on the main contacts, with auxiliary terminals taking 2x 0.5–1.5 mm² or 2x 0.75–2.5 mm². That covers most control wiring up to 10 AWG solid. The screw-type terminals are standard for panel builders — no special tooling needed. Operating temperature spans -25 to +60 °C, storage from -55 to +80 °C. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, which gives flexibility in tight enclosures but keep the arcing clearance of 10 mm upwards and 6 mm sideways per the spec.