What It Is and What It Does
The Siemens 3RT1045-1AL24 is a SIRIUS power contactor in the S3 frame size, designed for switching motor loads in industrial control panels. Its headline rating is 45 kW at 500 V under AC-3 duty (cite:), which means it handles the inrush and breaking of squirrel-cage motors up to that power level — the rating that governs real-world motor switching, not the higher resistive-load figure. The 24 V DC coil (cite:) draws 10 A at rated voltage, so verify your control transformer and fuse sizing against that pickup current. Mechanical endurance is listed at 10,000,000 operations typical (cite:), which for a contactor on a conveyor or pump running 100 cycles per hour gives about 11 years of service before mechanical wear becomes a concern. The AC-3 maximum switching rate of 1,000 operations per hour (cite:) sets the thermal limit for the arc chamber — sustained cycling above that rate accelerates contact erosion. Pollution degree 3 (cite:) means it's rated for industrial environments with conductive contamination, so no derating needed in typical panel conditions.
Mounting and Integration
Mounts via screw or snap-on onto 35 mm and 75 mm standard DIN rails (cite:), giving flexibility in panel layout. The S3 frame occupies 70 mm width, 146 mm height, and 188 mm depth (cite:,) — check your backpanel gland plate clearance, especially if the contactor sits near the enclosure wall. Side-by-side mounting is permitted (cite:), which saves rail space but requires attention to thermal derating if multiple contactors are ganged without spacing. Main circuit connections are screw-type terminals (cite:). Solid wire capacity is 2x (0.5... 1.5 mm²) and 2x (0.75... 2.5 mm²), max 2x (0.75... 4 mm²) (cite:); stranded accepts 2x (10... 50 mm²) (cite:). The IP20 rating on the front with cover or box terminal (cite:) means the contactor is finger-safe from the front but not sealed — suitable for enclosed panels, not washdown zones.