As versatile as your application

3RW soft starters

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  • soft start! SIRIUS soft starters are the best solution when direct-on-line or star/delta starting are not suitable for three-phase motors, because mechanical impacts in the machine or voltage dips in the power supply system can often cause problems. A full and comprehensive range of soft starters with intelligent functions offers a softer alternative for almost every application.

Go directly to the technical data of all our 3RW soft starters

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Soft starter Portfolio

High Performance

5,5-1.200 kW

SIRIUS 3RW55 soft starter High Performance

Due to its exceptional functionality, the intelligent SIRIUS 3RW55 soft starter can solve even the most difficult starting and stopping tasks simply and particularly gently. Integrated smart functions (for example, pump cleaning, pump stopping, automatic parameterization, condition monitoring) help operators to run their pumps smoothly. Thanks to the SIRIUS 3RW55 Failsafe soft starters with integrated Safe Torque Off (STO) functionality, safety-related applications can also be realized.


  • Three-phase controlled for optimal motor start
  • Integrated, safety-related shutdown for SIL 1/PL c and SIL 3/PL e (with STO)
  • ATEX/IECEx-certified for use in hazardous areas
  • Engineering in the TIA Portal
  • A wide range of communications interfaces (PROFINET, PROFIBUS, EtherNet/IP, Modbus)
  • Direct communication into cloud based solutions via OPC UA
  • Motor control and diagnostic data via a standard web browser without additional software
  • Integrated HMI (Human-Machine-Interface) with colour display
  • Media redundancy for reliable network availability
  • Integration in the process control system PCS 7 V9.0 SP2 with the 3RW5 block library

General Performance

5,5-560 kW

SIRIUS 3RW52 soft starter General Performance

The SIRIUS 3RW52 soft starter is an ideal alternative to star-delta starters. As an all-rounder, it covers all drive types.


  • Three-phase controlled for optimal motor start
  • Parameterization with rotary potentiometer
  • A wide range of communications interfaces (PROFINET, PROFIBUS, EtherNet/IP, Modbus)
  • HMI (Human-Machine-Interface) with display optional 
  • Engineering in the TIA Portal
  • Integration in the process control system PCS 7 V9.0 SP2 with the 3RW5 block library

Basic Performance

1,5-315 kW

SIRIUS 3RW30/3RW40/3RW50 soft starter Basic Performance

Thanks to their compact design, SIRIUS 3RW30/40/50 soft starters are the ideal solution for all standard applications.


  • Two-phase controlled for standard applications
  • Parameterization with rotary potentiometer
  • Optional communications interface (PROFINET, PROFIBUS, EtherNet/IP, Modbus)
  • Visualization of motor data via optional HMI or analog output
  • Integrated motor overload and intrinsic device protection
  • Engineering in the TIA Portal
  • ATEX/IECEx-certified for use in hazardous areas

Starter Kit "High Performance"

Test it now

Plug and play: install the software and set the parameters!

Test the new generation of 3RW55 soft starters and simply experience how easy commissioning is. With the SIRIUS Soft Starter ES software, you can set parameters, monitor and perform diagnostics for service tasks quickly and easily. You can set the device parameters of the 3RW55 directly from your PC or laptop.

Simulation Tools

Select and simulate

Simulation Tools

You can use the Simulation Tool for Soft Starters (STS) to select the right devices for your application – as a desktop application or optimized for your mobile device. Your selection is then automatically transferred to the Siemens Industry Mall ready for ordering via a link.


To the Simulation Tool for Soft Starters (STS)

Tutorial STS: How do I select the right 3RW soft starter for my application?


SIRIUS Sim enables an easy and quick test of functions and parameterizations at your desk. Afterwards, the parameterization can be downloaded into the real devices.

• Full parameterization of the high performance SIRIUS 3RW55 soft starters

• Complete navigation with the same menu structure of the 3RW5 high feature HMI

• Optional storage of the parameterization in a micro SD card to be downloaded afterward in the real device

• Simulation of startup, ramp down and operational phases as well as different error conditions


To the SIRIUS Sim

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Highlights at a glance

SIRIUS 3RW55 fail-safe soft starter features an integrated fail-safe digital input that directly connects to an E-STOP pushbutton, covering SIL 1 PL c applications. Apply a safety contactor and relay, and you’ll also achieve a SIL 3, PL e rating.

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