What it is and what it does
The Siemens 3RT1023-1BW40 is a SIRIUS-branded power contactor in the S0 frame size, designed for switching motor loads in control panels. It mounts via screw or snap-on onto 35 mm standard mounting rail per DIN EN 50022, with a width of 45 mm, height 85 mm, and depth 101 mm — a compact footprint for a 24 VDC-coil contactor rated to switch 10 A at 24 V and 2 A at 60 V in DC circuits. For AC motor duty, the AC-4 rating at 400 V is 8.5 A, covering reversing or inching applications where the contactor makes and breaks stalled-rotor current. AC-2 at 400 V is rated at 4 kW, suited for slip-ring motor starting. At 690 V the contactor handles 5.5 kW, and at 500 V it handles 4.5 kW — these are the motor power ratings for standard three-phase induction motors.
Coil and control circuit
The DC coil draws 5.4 W both for closing and holding — no power drop after pick-up, so the supply must sustain that continuously. Rated control supply voltage is 48 V DC. The contactor also carries DC switching ratings at 110 V (1 A) and 220 V (0.3 A), useful for breaking DC auxiliary loads in the same panel.
Short-circuit coordination and wiring
For Type 2 coordination (no damage to the contactor after a fault), the required upstream fuse is gL/gG 25 A. For Type 1 coordination (contactor may need replacement after fault), the fuse can be 63 A. Main circuit terminals accept screw-type connections: solid 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), max 2x (0.75...4 mm²), or stranded 2x (1...2.5 mm²), 2x (2.5...6 mm²), max 2x 10 mm². AWG equivalents are 2x (16...12), 2x (14...10), 1x 8.
Mounting and environment
Mounts on 35 mm DIN rail per EN 50022, screw or snap-on. Side-by-side mounting is permitted with 6 mm spacing to adjacent devices. Front face is IP20 (finger-safe); the terminals themselves are IP00 (no protection), so the panel enclosure provides the overall ingress protection. Operating temperature range is -25 to +60 °C, with a maximum operating altitude of 2 000 m. Pollution degree 3 (industrial environment with conductive pollution).