What this contactor is and where it fits
The Siemens 3RT2037-3SB30 is a SIRIUS power contactor in size S2, rated for switching motor loads and resistive circuits in industrial control panels. It carries three main poles and an auxiliary switch block, with spring-type terminals for tool-less wiring of 2x (0.5... 2.5 mm²) solid or stranded conductors. The coil accepts 21... 33 V (rated value), drawing 2 VA at both 50 Hz and 60 Hz. Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, with +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward — useful when panel layout forces an unusual orientation.
Key ratings and what they mean for your circuit
The 3RT2037-3SB30 is a 3-pole contactor (18... 1 main contacts) sized for moderate motor loads. The AC-3 switching frequency of 700 operations per hour (max) tells you it can handle frequent starts for conveyors or pumps without overheating the arc chamber. AC-4 max of 200 1/h covers plugging or inching duty — lower because each reversal stresses the contacts harder. Mechanical life is 5 000 000 cycles typical, and the MTBF of 52 y reflects a robust solenoid design. Arcing time runs 10... 20 ms; operate time for both AC and DC coils is 30... 55 ms, consistent across the voltage range. Inrush current peak is 2.2 A — useful when sizing the control transformer.
Auxiliary contact ratings and coil pickup
The built-in auxiliary switch is rated for 10 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, and 0.9 A at 125 V — enough to drive a PLC input or a small relay in the same panel. Coil pickup is 0.8 x rated voltage (initial value), with a full-scale value of 1.1; dropout margin is tight, so verify the control supply stays above 21 V under load. Ambient operating range is -25... +60 °C; storage range is -55... +80 °C. Clearance requirements: 10 mm upwards, forwards, and downwards, 6 mm at the side — plan the DIN-rail spacing accordingly.