Siemens 3RW4037-1BB15 Three-Phase Soft Starter

Siemens 3RW4037-1BB15 is a SIRIUS Soft Starter (S2 family) for 3‑phase motors, providing controlled inrush and smooth ramp‑up to protect mechanical systems and reduce electrical disturbance. Designed for 400–600 V AC networks, it handles up to 63 A and supports motors up to 37 kW at 500 V (30 kW at 400 V). The device provides an integrated bypass contact system and thyristor‑based soft‑start control, plus intrinsic device protection and motor overload protection. It offers external reset input and adjustable current limitation, with screw terminals for straightforward wiring, and a control supply range of 110–230 V AC or DC. Rated for 50/60 Hz operation and insulation up to 600 V, the 3RW4037‑1BB15 is a compact solution for applications like conveyors, pumps, fans, and other industrial machines where a gentle start reduces mechanical stress and electrical peak currents. The unit maintains IP20 protection in standard installations and is compatible with common control circuits thanks to its universal coil supply. This Siemens soft starter delivers a reliable, straightforward method to sequence motor start‑ups without the need for a full VFD when speed control is not required, making it a practical upgrade for existing 3‑phase motor circuits in factory settings.