What it is and what it does
The Siemens 3RT1024-3BW40 is a SIRIUS 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 DIN rail per EN 50022, so it integrates directly into a standard panel layout without adapters. Rated at 5.5 kW in AC-2 duty at 400 V, this contactor handles wound-rotor motor starting and reversing applications. For AC-4 reversing duty at 400 V, it carries 12.5 A — the rating that governs plugging and inching cycles where the contactor makes and breaks stalled rotor current.
Coil and control circuit
The DC magnet coil draws 5.4 W during both closing and holding, which simplifies the control transformer sizing — no inrush peak to budget for. The coil operates across a range of DC voltages; at 24 V rated value it switches 10 A on the auxiliary contacts, and at 60 V rated value it switches 2 A.
Coordination and protection
For Type 2 coordination (no damage to the contactor under short circuit), the required upstream fuse is gL/gG 25 A. For Type 1 coordination (contactor may need replacement after fault), the fuse can be gL/gG 63 A. This lets the panel builder choose between protecting the contactor or minimizing fuse size, depending on the application's criticality.
Mounting and environment
The contactor occupies 45 mm width on the DIN rail, with a depth of 100 mm and height of 85 mm. Side-by-side mounting is permitted, so multiple contactors pack tightly in a row without derating. The front face carries IP20 protection; the terminals themselves are IP00, meaning the wiring compartment expects enclosure protection from the panel. Operating temperature range is -25 to +60 °C, with a maximum operating altitude of 2 000 m. Pollution degree 3 means it tolerates conductive pollution in industrial atmospheres — typical for a control panel not in a clean room.