What this SIRIUS contactor is and what it handles
The Siemens SIRIUS 3RT1023-1BB44-1AA0 is a power contactor in the S0 frame size, built for switching three-phase motor loads in control panels. It carries 3 normally-open main contacts and a 24 V DC coil that draws a steady 5.4 W for both closing and holding — no power drop once pulled in, so the coil supply needs to sustain that draw continuously. The AC-3 rating at 400 V is 4 kW, which covers a standard 4-pole induction motor up to that output; the AC-4 rating at 400 V is 8.5 A, for reversing or inching duty where the contacts make and break under load more often. The contactor mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, and the 45 mm width means it takes a single 45 mm slot in a standard enclosure — no overhang. The IP20 front protection is typical for panel-mounted gear; the terminals themselves are rated IP00, so the panel door or a terminal cover provides the final touch protection.
Coordination and wiring reality
For short-circuit protection, Type 1 coordination requires a 63 A gL/gG fuse; Type 2 coordination needs a 25 A gL/gG fuse. The difference matters for maintenance philosophy: Type 2 leaves the contactor usable after a fault, Type 1 may require replacement. The main circuit terminals accept screw-type connections, with solid wire up to 2x 4 mm² or stranded up to 2x 10 mm² — enough for the motor feed on this frame size. The contactor is rated for pollution degree 3, which means it's suited for industrial environments where conductive dust or occasional condensation is present — no need for an additional conformal coating in a typical panel. Operating temperature spans -25 to +60 °C, so it handles the heat inside a crowded cabinet near a press or drive without derating at the top end.
Mounting and integration notes
Snap it onto a 35 mm DIN rail — the S0 frame clips in without tools. Side-by-side mounting is allowed with zero clearance between units, so you can pack several in a row without derating for heat buildup in still air. The 150 mm depth leaves room in a 200 mm deep enclosure for wiring behind the contactor. The auxiliary contact block (not included) mounts on the front; the contactor has two instantaneous auxiliary contact positions available. The 10 million mechanical cycles typical means it outlasts most motor starts in a production line before a rebuild is needed.