What it is and where it fits
The Siemens SIRIUS 3RT1023-1BW44 is a power contactor in the S0 frame size, designed for switching motor loads in industrial control panels. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, so it drops into any standard panel layout without adapter plates. The 48 VDC coil draws 5.4 W both on pick-up and hold, which simplifies the DC supply sizing — no inrush spike to budget for. The contactor is rated for AC-4 duty at 8.5 A at 400 V, meaning it can handle the severe switching conditions of plugging or inching motor loads where the contacts make and break under full current. Motor power ratings reach 4.5 kW at 500 V and 5.5 kW at 690 V, covering common European and export voltage levels. The IP20 front protection keeps fingers and tools out of the live terminals inside the enclosure; the terminals themselves are rated IP00, so the contactor must live inside a cabinet, not out on the plant floor.
Environment and wiring
Rated for operation from -25 °C to +60 °C, so it survives the ambient heat inside a cement plant control room or a steel mill MCC. Pollution degree 3 means it tolerates conductive dust and humidity — no conformal coating needed for most industrial atmospheres. Main circuit terminals accept solid conductors from 2x (0.5... 1.5 mm²) up to 2x (0.75... 4 mm²), and stranded conductors from 2x (1... 2.5 mm²) up to 2x 10 mm². That range covers standard motor feeder cables up to about 6 AWG without lugging. Side-by-side mounting is allowed with a 6 mm gap to the side, keeping panel density high. Short-circuit coordination is specified: for Type 2 coordination (limited damage after a fault), use a gL/gG fuse rated 25 A; for Type 1 (replace contactor after fault), use 63 A. The reference code per DIN EN 81346-2 is Q, which maps to power switching equipment in the plant documentation tree.