What it is and what it does
The Siemens 3RT1023-1AU00 is a SIRIUS power contactor in the S0 frame size, designed for switching three-phase motor loads in industrial control panels. It carries 4.5 kW at 500 V and 5.5 kW at 690 V in AC-3 duty, which is the standard motor-switching category — meaning it handles the inrush and breaking of induction motors at those power levels without welding the contacts. The 3-pole main contact block has 3 normally-open contacts and no normally-closed contacts, so it's a straight motor starter contactor, not a reversing or star-delta configuration.
Mounting and integration
Mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022. The 45 mm width means it occupies one standard modular unit, so it fits neatly into a row of motor starters or alongside a thermal overload relay. The front face carries an IP20 rating — safe for finger contact in an enclosure — while the terminals themselves are IP00, meaning they rely on the panel's own protection. Side-by-side mounting is allowed with no derating gap, so you can pack multiple contactors tight on the rail.
Terminal and wiring details
Main circuit terminals are screw-type, accepting solid conductors: 2x 0.5–1.5 mm², 2x 0.75–2.5 mm², or max 2x 0.75–4 mm². For stranded wire, the range is 2x 1–2.5 mm², 2x 2.5–6 mm², or max 2x 10 mm². AWG equivalents are 2x 16–12, 2x 14–10, and 1x 8. This covers most panel wiring from control circuits up to moderate motor feeders. The pollution degree is 3 (conductive or dry non-conductive pollution), typical for industrial environments.
Coil and auxiliary ratings
The coil is rated for 50 Hz at 240 V, with an operating range of 0.8 to 1.1 times the rated voltage at 50 Hz. That means it picks up reliably down to about 192 V and holds in up to 264 V. For auxiliary contacts (not built-in, but add-on blocks are available), the rated currents at various voltages are: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V. The mechanical life is 10 million operations typical.
Short-circuit protection and coordination
For Type 2 coordination (no damage to the contactor after a short circuit), the required upstream fuse is gL/gG 25 A. For Type 1 coordination (contactor may need replacement after a fault), the fuse can be gL/gG 63 A. This lets you balance protection level against fuse size depending on the panel's selectivity requirements.