What it is and what it does
The Siemens SIRIUS 3RT1024-1BG44 is a Size S0 power contactor built for switching motor loads and resistive circuits in control panels. Its AC-12 rating of 10 A tells you the maximum continuous current it can handle in a resistive or lightly inductive load — think heater banks or transformer primaries, not motor starts. For motor duty, the AC-4 rating at 400 V of 12.5 A covers plugging and inching applications where the contactor breaks full motor current; the AC-2 rating at 400 V of 5.5 kW suits slip-ring motor starting. The 45 mm width means it fits a standard 35 mm DIN rail per EN 50022, and side-by-side mounting is allowed with a 6 mm gap, so you can pack several in a row without derating.
Coil and control
The DC magnet coil draws 5.4 W for both closing and holding, so the control circuit sees the same load whether the contactor is pulling in or staying sealed. That matters for DC-supplied PLC outputs or relay drivers — no inrush spike to manage. The coil's operating range covers -25 to +60 °C ambient, and the contactor is rated for pollution degree 3, meaning it tolerates conductive dust and condensation typical in industrial enclosures.
Wiring and protection
Main circuit terminals are screw-type, accepting 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or max 2x (0.75 to 4 mm²) solid/stranded — plenty of range for panel wiring up to 10 mm² max per conductor. For short-circuit protection, Type 2 coordination (no damage to the contactor) requires a 25 A gL/gG fuse; Type 1 coordination (contactor may need replacement) allows up to 63 A gL/gG. The front face carries IP20 finger protection; the terminal area is IP00, so keep live parts guarded inside the panel.