What It Is and What It Does
The Siemens SIRIUS 3RT1034-3BF40 is a size S2 power contactor designed for switching motor loads and resistive loads in industrial control panels. It carries a 110 V coil and is rated for AC-4 duty at 29 A at 400 V, meaning it can handle severe inrush and plugging duty for motors up to that current. At 500 V it is rated for 18.5 kW motor output, and at 690 V for 10 kW. The contactor mounts on a 35 mm DIN rail per EN 50022, using either screw or snap-on fastening. The main circuit uses screw-type terminals, accepting solid wires from 0.25 to 2.5 mm² and stranded wires from 0.75 to 25 mm². The front face is IP20 rated for finger-safe touch; the terminal area is IP00, so it requires enclosure protection during installation. Pollution degree 3 means it is suited for industrial environments with conductive pollution.
Key Ratings and What They Mean for Fit
The AC-4 rating at 29 A at 400 V is the critical spec for applications with frequent reversing, inching, or plugging — common in crane, hoist, or conveyor reversing drives. The AC-2 rating at 15 kW at 400 V covers slip-ring motor starting. For resistive loads (AC-1), the maximum switching frequency is 1200 operations per hour; for AC-3 (standard squirrel-cage motor start/run) it is 1000 ops/h, and for AC-4 it drops to 250 ops/h due to the heavier electrical wear. Mechanical endurance is rated at 10 million cycles typical. The auxiliary contact ratings at 24 V (10 A), 110 V (1 A), and 230 V (6 A) cover typical PLC or relay interface levels. The DC operating time is 20 to 30 ms, and arcing time is 10 to 15 ms, which matters for coordination with upstream protection devices.
Integration and Mounting
Mounts on a 35 mm DIN rail per EN 50022 via screw or snap-on. Side-by-side mounting is permitted without derating, which simplifies panel layout. Dimensions: width 55 mm, height 112 mm, depth 130 mm. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. The contactor is rated for use in enclosures with pollution degree 3.