What it is and where it fits
The Siemens 3RT2637-1NB35 is a SIRIUS 3RT2 contactor with a 20-33 V AC/DC coil, screw-type coil terminals, and a compact 65 mm width that screws or snaps onto 35 mm DIN rail per DIN EN 50022. The 130 mm depth and 114 mm height keep the footprint tight inside a control panel — no extra clearance needed beyond the standard DIN-rail envelope.
Auxiliary contact ratings — what they mean for your circuit
The built-in auxiliary contacts are rated 6 A at 24 V, 6 A at 230 V, and 3 A at 400 V — so they handle PLC-level signals at 24 VDC and small motor-starter interlocking at 230 VAC without an external relay. At 400 V the 3 A rating covers most contactor feedback and status loops in a 400 V three-phase panel. The 0.9 A at 125 V and 0.3 A at 220 V give the DC switching curve for control transformers or DC bus monitoring.
Mounting and wiring
Mounts on 35 mm DIN rail per DIN EN 50022 via screw or snap-on fastening. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward — useful when the panel layout forces an odd angle. Solid wire capacity: 2x (0.5-1.5 mm²), 2x (0.75-2.5 mm²), 2x 4 mm². Stranded: 2x (10-35 mm²) or 1x (10-50 mm²). The screw-type coil terminals accept the same range, so no special crimp tools needed for the control circuit.
Switching frequency and operating times
Maximum switching frequency drops with voltage: 100 operations/hour at 230-240 V, 80/h at 400 V, 50/h at 480 V, 45/h at 500 V, 32/h at 600 V, and 25/h at 690 V. That curve tells you the contactor is sized for moderate-duty motor starting and general switching — not high-speed jogging or continuous cycling. Operating time is 30-55 ms for both AC and DC coil supplies; arcing time runs 10-20 ms.
Temperature range
Rated for operation from -25 to +60 °C, storage from -55 to +80 °C. The storage range exceeds the operating range — that limit governs handling and shipping, not running conditions.