As versatile as your application

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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.

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Soft starter portfolio – Focus on highlights

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.


  • Three-phase controlled for optimal motor start
  • Engineering in the TIA Portal
  • A wide range of bus connections (PROFINET, PROFIBUS, EtherNet/IP, Modbus)
  • Integrated HMI (Human-Machine-Interface) with colour display
  • Electrical ruggedness
  • For drives with power ratings from 5.5 to 1,200 kW
  • Media redundancy for reliable network availability

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 bus connections (PROFINET, PROFIBUS, EtherNet/IP, Modbus)
  • HMI (Human-Machine-Interface) with display optional 
  • Electrical ruggedness
  • For drives with power ratings from 5.5 to 560 kW

Basic Performance

1,5-250 kW

SIRIUS 3RW30/3RW40 soft starter Basic Performance

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


  • Two-phase controlled for standard applications
  • Parameterization with rotary potentiometer
  • Integrated motor overload and intrinsic device protection
  • Electrical ruggedness
  • For drives with power ratings from 1.5 to 250 kW

Starter Kit "High Performance"

Test it now

Plugand 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 Tool (STS)

Select and simulate

Simulation Tool for Soft Starters (STS)

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.