SIRIUS Size S2 power contactor — 3RT2037-1NB34
The Siemens SIRIUS 3RT2037-1NB34 is a Size S2 power contactor with an 18-pole main contact set, designed for screw and snap-on mounting onto 35 mm DIN rail per DIN EN 60715. The coil accepts 20-33 V AC/DC, drawing 2 VA at 50 or 60 Hz, with an inrush peak of 3 A. Screw-type coil terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded wire.
Duty ratings and switching frequency
Switching frequency varies by duty class: AC-1 (resistive) max 800 operations/hour, AC-2 (slip-ring motor) 400 ops/h, AC-3 (squirrel-cage motor) 700 ops/h, AC-3e (enhanced AC-3) also 700 ops/h, and AC-4 (plugging/inching) 200 ops/h. The AC-3 and AC-3e ratings match typical motor-starting applications — the 700 ops/h ceiling means it handles frequent cycling on conveyors or pump stations without exceeding thermal limits. Operate time is 30-55 ms for both AC and DC coils, with an arcing time of 10-20 ms. Mechanical life is rated at 10 million operating cycles typical.
Mounting and environmental flexibility
Mounting position allows +/-180° rotation on a vertical surface, plus +/-22.5° forward/backward tilt. Clearance distances: 10 mm upwards, forwards, and downwards; 6 mm at the sides. The envelope measures 114 mm high, 55 mm wide, and 174 mm deep — the 55 mm width means it occupies three standard 18 mm DIN-rail module spaces, so panel fill factor is straightforward to estimate. Operating temperature range is -25 to +60 °C; storage range extends from -55 to +80 °C. The operating range covers most indoor industrial enclosures without derating, though sustained ambient above 60 °C would require thermal review.
Auxiliary contact ratings
The contactor comes without an auxiliary switch block (Auxiliary Switch: No). For applications requiring auxiliary contacts, a separate add-on block must be ordered. When added, the auxiliary contact breaking capacity at 24 V rated value is 6 A, at 48 V and 60 V it is 2 A, at 110 V it is 1 A, at 125 V it is 0.9 A, and at 220 V it is 0.3 A.