What it is and what it does
The Siemens SIRIUS 3RT1035-1DB44 is a size S2 power contactor with a 24 VDC coil, designed for switching motor loads in industrial control panels. It mounts on a 35 mm DIN rail per DIN EN 50022 and uses screw-type terminals for the main current circuit. For AC-3 motor duty — the standard squirrel-cage motor start/stop — this contactor is rated 22 kW at 500 V and 11.4 kW at 690 V. The AC-3 maximum mechanical switching rate is 1 000 operations per hour, reflecting the thermal recovery time between starts. The AC-4 rating (plugging/reversing/inching duty) is 35 A at 400 V, with a maximum rate of 300 operations per hour — that's the more punishing duty cycle where the contactor makes and breaks full locked-rotor current.
What the ratings mean for fit
The 24 VDC coil pulls in at 20 to 25 ms and drops out with similar timing — fast enough for most PLC-driven sequences, but not a high-speed DC-switching contactor. The auxiliary contact ratings at 24 V (10 A), 60 V (2 A), 110 V (1 A), 220 V (0.3 A), 230 V (6 A), and 400 V (3 A) cover the typical control-voltage levels found in mixed AC/DC panels. Pollution degree 3 means this contactor is rated for the conductive-dust and humidity conditions typical in industrial enclosures without climate control. The IP20 front and IP00 terminal area confirm it needs an enclosure — it's not a standalone outdoor device. Side-by-side mounting is permitted, which means no derating for heat buildup when contactors are ganged on the rail — but the 55 mm width per unit still governs your DIN-rail budget.
Termination and wiring
Main circuit terminals accept solid conductors 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), and max 2x (0.75 to 4 mm²). Stranded conductors up to 2x (0.75 to 25 mm²) fit, and the minimum permissible conductor at 40 °C is 16 mm² — that's the thermal limit for the terminal material, not a crimp restriction. The auxiliary and coil terminals accept 2x (0.75 to 16 mm²) solid or stranded. This covers the typical control wiring range from 1.5 mm² for signal circuits up to 16 mm² for a long coil feed.
Lifecycle and sourcing
RoHS compliance is dated to 05/01/2012, covering the EU RoHS substance prohibitions. The SIRIUS series carries CE, UL, CSA, and IEC certifications as standard for the brand family. This part is sourced to order against an RFQ through the standard Siemens distribution channel. No broker or last-time-buy urgency applies.