What it is and what it does
The Siemens 3RT1023-1BD44 is a SIRIUS power contactor in the Size S0 frame, designed for switching motor loads in industrial control panels. It mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 50022, fitting a standard panel footprint at 45 mm wide, 85 mm tall, and 150 mm deep. With a 24 VDC coil drawing 5.4 W both for closing and holding, it's sized for continuous-duty control circuits. The main contacts are screw-type terminals accepting 2x (0.5 to 4 mm²) solid or 2x (1 to 10 mm²) stranded — covers most panel wiring up to 10 mm². Rated switching capacity varies by voltage and duty: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 4.5 kW at 500 V or 5.5 kW at 690 V for AC-3 motor starting. For AC-2 duty at 400 V it's rated 4 kW; AC-4 at 400 V delivers 8.5 A for reversing or inching applications.
Where it fits and what it connects to
Snap it onto a 35 mm DIN rail in the enclosure — the 45 mm width leaves room for adjacent devices with side-by-side mounting supported. The IP20 front protection means it's safe for finger contact inside a closed panel; the terminals themselves are IP00, so live parts are exposed during wiring. Operating temperature range is -25 to +60 °C, with a maximum altitude of 2 000 m and pollution degree 3 (conductive pollution, typical for industrial environments). The 6 mm clearance to side walls is the minimum for heat dissipation and arc containment. Two instantaneous auxiliary contacts (NO/NC configurable) are built in for feedback or interlocking. For short-circuit coordination, Type 1 requires a 63 A gL/gG fuse; Type 2 requires a 25 A gL/gG fuse — choose based on whether you accept contact weld in a fault.