What It Is and Where It Fits
The Siemens SIRIUS 3RT1034-1BB44-3MA0 is a power contactor in the S2 frame size, designed for switching motor loads in industrial control panels. It carries a 24 VDC coil and terminates main circuits via screw-type terminals. The part snaps onto a 35 mm DIN rail per EN 50022, so it integrates directly into a standard panel layout without adapter plates.
What the Ratings Mean for Your Motor Load
The headline motor ratings tell you what three-phase induction motor this contactor can switch in normal duty. At 500 V AC-3 (starting and running a squirrel-cage motor), it is rated 18.5 kW; at 690 V AC-3, 10 kW. That 18.5 kW at 500 V is the figure that governs most 400/480 V line applications — the contactor handles the inrush and break current for motors up to that power. For AC-2 duty (slip-ring motors, partial-load switching) at 400 V, it is rated 15 kW. For AC-4 (plugging, inching, reversing), the rating drops to 29 A at 400 V — a lower continuous capability because the contactor sees more frequent arc interruption. The switching frequency limits back this up: 1 000 cycles/hour for AC-3, 250 cycles/hour for AC-4. If your application cycles faster than that, the contactor will overheat the arc chamber.
Coil and Control Circuit Details
The 24 VDC coil draws 10 A at rated voltage — that is the inrush to pull the armature in, not the holding current. The operate time is 20 to 30 ms DC, with an arcing time of 10 to 15 ms. For DC coil voltages beyond 24 V, the holding currents scale down: 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, 6 A at 230 V, 3 A at 400 V. The coil is polarity-sensitive on DC; verify the free-wheel diode or suppression network orientation before wiring.
Mounting and Environmental Fit
The S2 frame measures 55 mm wide, 112 mm high, and 179 mm deep — a compact footprint for a contactor in this power class. It supports side-by-side mounting without derating, so you can gang multiple contactors on the same DIN rail without air gaps. The front face is IP20 (finger-safe), while the terminals are IP00 (no protection), meaning the terminals must be inside a closed panel or guarded. Pollution degree 3 means it tolerates conductive dust and humidity typical of industrial floors. Operating temperature spans -25 to +60 °C; storage from -55 to +80 °C. The mechanical endurance is 10 million cycles, so the armature and spring set outlast most motor starts in a typical line.
Wiring and Conductor Sizing
The screw terminals accept a wide range of conductors. For solid wire: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or up to 2x (0.75 to 4 mm²). For stranded wire: 2x (0.75 to 25 mm²). For solid or stranded combined: 2x (0.75 to 16 mm²). At 40 °C ambient, the minimum permissible cross-section is 16 mm² — that is the thermal derating floor for full rated current. The terminal design allows two conductors per clamp, useful for daisy-chaining control power.