The Siemens 3RW4037-2BB04 is a SIRIUS soft starter in size S2, rated 63 A at 40 °C for standard motor starting duty. The adjustable current limitation and built-in motor overload protection let you set the starting ramp to match the load without adding an external relay.
The S2 footprint is 55 mm wide, 160 mm high, and 170 mm deep, with clearance requirements of 60 mm upward, 40 mm downward, and 30 mm at the side. For vertical mounting surfaces, the unit can be rotated ±90° with an additional fan, or tilted ±22.5° front-to-back; without the fan, rotation is limited to ±10°.
Environmental and Electrical Ratings
Derating begins above 40 °C: the unit delivers 58 A at 50 °C and 53 A at 60 °C. Insulation voltage is rated 600 V, and the maximum motor cable length is 300 m.
Main power connections use screw-type terminals. The main circuit accepts stranded wire from 1.5 mm² to 25 mm² (two conductors per clamp) and solid wire from 0.25 mm² to 2.5 mm² (two conductors per clamp). Auxiliary contact terminals accept 24 AWG to 14 AWG. The unit supports an external reset and provides a red fault signal display.