What it is and where it fits
The Siemens 3RT2037-3NP30 is a SIRIUS power contactor in Size S2, designed for switching motor loads and resistive loads in industrial control panels. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, and the spring-type terminals accept 2x (0.5... 2.5 mm²) solid or stranded conductors — no screwdriver torque needed for the power wiring, which speeds panel assembly and reduces loose-terminal callbacks. The coil accepts a wide control supply range of 175... 280 V AC/DC, with a holding consumption of 2 VA at both 50 Hz and 60 Hz. The inrush current peaks at 5 A, so the control transformer or PLC output driving it must be sized for that surge, not just the steady-state VA.
Key ratings and what they mean for your circuit
The main contacts are configured as 18... 1 — that's three normally-open power poles plus one normally-open auxiliary, with the auxiliary switch already built in. The auxiliary contact is rated at 10 A at 24 V, 2 A at 48 V, 2 A at 60 V, 1 A at 110 V, 0.9 A at 125 V, and 0.3 A at 220 V — these are the maximum break currents for the auxiliary circuit; if you're switching a PLC input or a small relay, stay within these limits per the voltage you're using. Switching frequency limits: 800 operations per hour at AC-1 (resistive load), 400 at AC-2 (slip-ring motor), 700 at AC-3 (squirrel-cage motor), and 200 at AC-4 (plugging/inching). If your application cycles faster than these rates, the contactor will overheat — the AC-4 ceiling of 200 ops/h is the one that governs severe-duty reversing or jogging. Mechanical service life is rated at 10,000,000 operations typical. Arcing time is 10... 20 ms, and switch-on delay is 30... 55 ms for both AC and DC.
Environmental limits and mounting flexibility
Operating temperature range is -25... +60 °C; storage range is -55... +80 °C. The contactor can be mounted in any orientation: +/-180° rotation on a vertical surface, and tilted forward/backward by +/-22.5° on a vertical surface. Clearance distances: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm to the side — these are the minimum air gaps to adjacent metalwork or other devices; crowding it tighter risks flashover or reduced heat dissipation. Dimensions: 114 mm high, 55 mm wide, 130 mm deep. The 55 mm width is a standard Size S2 footprint, so it fits existing DIN-rail layouts without re-spacing.
Lifecycle and sourcing posture
The lifecycle stage is listed as current, meaning Siemens continues to manufacture and support this order code. It is not subject to a phase-out or last-time-buy notice at this time.