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.
Mounting and environmental flexibility
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. The operating range covers most indoor industrial enclosures without derating, though sustained ambient above 60 °C would require thermal review.
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.