What it is and what it does
The Siemens 3RT1034-1BB40-ZW96 is a SIRIUS power contactor in size S2, rated for switching motor loads and resistive circuits in industrial control panels. It carries a 24 VDC coil and is designed for screw and snap-on mounting onto 35 mm standard mounting rail per DIN EN 50022, so it drops straight into a standard DIN-rail panel without extra hardware. The contactor is rated for AC-3 duty at up to 1 000 switching cycles per hour, which covers the normal motor-starting profile for pumps, fans, and conveyors. For heavier switching like inching or plugging (AC-4), the maximum rate drops to 250 1/h — plan the cycle count if your application includes frequent reversing or jogging. The main circuit uses screw-type terminals. Solid wire acceptance covers 2x (0.5... 1.5 mm²) and 2x (0.75... 2.5 mm²), up to max 2x (0.75... 4 mm²). Stranded wire goes up to 2x (0.75... 25 mm²). That range covers most panel wiring from control-circuit tails to motor feeders without needing adapters.
Key ratings and what they mean for fit
The 24 VDC coil draws 10 A at rated voltage. That's the inrush to latch the armature; once sealed, the holding current is lower. The arcing time at DC is 20 to 30 ms, and the overall arcing time is 10 to 15 ms — fast enough for most control schemes but check your PLC cycle time if you're monitoring auxiliary contacts for feedback. The auxiliary contact ratings span multiple voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 0.3 A at 220 V DC. The 400 V AC rating of 3 A is typical for signaling back to a 400 V control circuit; the 220 V DC rating of 0.3 A is the limit for DC switching — inductive DC loads will need a diode or RC snubber across the load. Motor power ratings: 18.5 kW at 500 V (AC-3), 15 kW at 400 V (AC-2), and 10 kW at 690 V. For AC-4 at 400 V, the contactor is rated at 29 A. If you're switching a motor above 18.5 kW at 500 V, you need a larger frame (size S3 or S6).
Where it fits and how it mounts
The contactor measures 55 mm wide, 112 mm high, and 130 mm deep — that's the S2 footprint. Side-by-side mounting is permitted, so you can gang multiple contactors on the same DIN rail without spacing. The IP20 front enclosure means it's protected against fingers and solid objects larger than 12 mm; the terminals themselves are IP00, so the panel enclosure must provide the overall IP rating. Operating temperature range is -25 to +60 °C, storage is -55 to +80 °C. Pollution degree 3 means it's suitable for industrial environments with conductive pollution (like dust or condensation) — no extra conformal coating needed for most dry indoor panels.