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

7.5- 400 HP

SIRIUS 3RW55 & 3RW55 Failsafe soft starters High Performance

Due to its innovative torque control, the 3RW55 can be used to drive up to 1000 hp at 480VAC for inline circuits or 1700 hp at 480VAC for inside-delta circuits. The optional communication module for PROFINET High Feature with 2 ports, facilitates media redundancy in a ring topology. This makes it easier on the user and ensures maximum operating convenience.


The 3RW55 Failsafe soft starter features an integrated fail-safe digital input for directly connecting the EMERGENCY STOP, and thus covers SIL 1 STO applications. With their modern hybrid switching technology, the 3RW55 Failsafe soft starters offer efficient switching for long-term, energy-saving use.


  • 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 motors with power ratings from 7.5 to 1700 HP
  • Media redundancy for reliable network availability

General Performance

7.5- 750 HP

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 motor 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 motors with power ratings from 7.5 to 750 HP

Basic Performance

1.5-400 HP

SIRIUS 3RW30/3RW40/3RW50 soft starters 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
  • Integrated motor overload and intrinsic device protection
  • Electrical ruggedness
  • For motors with power ratings from 1.5 to 400 HP

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.

SIRIUS 3RW55 Failsafe soft starter featuring 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 can achieve a SIL 3, PL e rating.

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