Siemens SIRIUS 3RT1024-1AL24 — Power Contactor, S0 Frame, 24 VDC Coil
The Siemens SIRIUS 3RT1024-1AL24 is a power contactor in the S0 frame size, designed for switching motor loads and resistive circuits in industrial control panels. It carries a 24 VDC coil and is rated for AC-4 duty at 12.5 A at 400 V — that's the category for reversing or inching motor starts where the contactor makes and breaks the motor current at full load, not just the inrush. Mounting is screw or snap-on onto 35 mm DIN rail per EN 50022, which means it drops into a standard panel rail without adapter plates. The 45 mm width (three module spaces) leaves room for auxiliary contact blocks alongside. Operating temperature range is -25 to +60 °C during operation, with a maximum altitude of 2,000 m.
Motor Duty and Coordination
For motor switching, the AC-4 rating at 12.5 A at 400 V is the figure that governs plugging or jogging applications where the contactor opens under load. The AC-2 rating at 5.5 kW at 400 V covers slip-ring motor duty. For resistive loads (AC-12), the contactor handles up to 10 A. Type 1 coordination requires a 63 A gL/gG fuse; Type 2 coordination requires 25 A. That's the short-circuit protection the contactor needs to survive a fault without welding its main contacts — the 25 A fuse for Type 2 keeps let-through energy low enough that the contactor can be re-energised after clearing the fault. The auxiliary contact block carries 2 N/O instantaneous contacts, rated at 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for feedback to a PLC or to seal in the coil circuit.
Termination and Wiring
Main circuit terminals accept screw-type connections: solid or stranded wire from 1 to 6 mm² (2x 1–2.5 mm², 2x 2.5–6 mm², max 2x 10 mm²). The coil terminals accept finer wire: 0.5 to 4 mm² (2x 0.5–1.5 mm², 2x 0.75–2.5 mm², max 2x 0.75–4 mm²). AWG equivalents are 2x 16–12 and 2x 14–10 for the main circuit, 1x 8 maximum. IP20 protection on the front of the enclosure keeps fingers out; the terminal area is IP00, so live parts are exposed when the cover is off — standard for panel-mounted contactors where the enclosure door provides the final barrier. Side-by-side mounting is allowed with a 6 mm gap to the side, which means you can pack contactors tightly on the rail without derating, as long as the ambient stays within the -25 to +60 °C range.