As versatile as your application

Go for a

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  • soft start! The 3RW5 family of soft starters is a comprehensive soft starter portfolio that has been developed for a wide range of applications and is simple to select, install, and configure. These starters are ready for the Internet of Things (IoT), being easily integrated into most industrial communication networks. Communications via Profinet, Modbus and Ethernet IP, along with HMI panels, are available across the entire product range.

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

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Soft starter portfolio

High Performance

7.5 - 1000 HP

SIRIUS 3RW55 high performance soft starter

The SIRIUS 3RW55 soft starter offers comprehensive functionality. It efficiently performs complex starting and stopping tasks. The integrated smart functions (such as pump cleaning, pump stopping, automatic parameterization and condition monitoring) support users in the smooth operation of their plant.


  • Three phases controlled for application flexibility
  • Compact size - Less than 8" deep up to 1000HP, easy to fit into MCCs, shallow cabinets and retrofits
  • Five available communication protocols: PB, PN-std, PN-HF, MB-TCP, EIP (future), MB-RTU (future)
  • HMI with color display, local interface and a slot for microSD memory card
  •  Wide range of control voltages: 24 V AC/DC and 110 - 250 V AC

General Performance

7.5 - 400 HP

SIRIUS 3RW52 general performance soft starter

The SIRIUS 3RW52 soft starter is the ideal alternative for star-delta starting applications. It is applicable for any type of motor.


  • Three phases controlled for application flexibility
  • Selectable analog or thermistor input for optimal protection of motor and load
  • Flexible HMI choices – Install the high feature, standard, or omit the display based on the application requirements.
  • Five available communication protocols: PB, PN, MB-TCP, EIP (future), MB-RTU (future)
  • Operator panel with optional display
  • Wide range of control voltages: 24 V AC/DC and 110 - 250 V AC

Basic Performance

1.5 - 300 HP

SIRIUS 3RW30/3RW40 basic performance soft starters

The SIRIUS 3RW30/40 soft starter is the ideal alternative starter for standard applications.


  • 2-phase control for standard applications
  • Parameterization over rotary setting elements
  • Integrated motor overload protection and intrinsic device protection
  • Electrical robustness
  • For drives in performance classes from 1.5 to 300 HP


7.5 - 900 HP

Enclosed 3RW4 Soft Starters

The family of SIRIUS 3RW40 and 3RW44 Soft Starters are available as stand alone enclosed control designs in combination and non-combination configurations through 900HP

The Class 73 is a non-combination style soft starter offering. They come standard with a choice of Type 1, 3R, 12, 4 or 4X NEMA rated enclosure, a control transformer, soft starter with built-in overload and bypass, line side power terminal block, and a reset pushbutton. 

The Class 74 offering includes all of the features of the Class 73, but in a combination style design. Standard options are either a circuit breaker or fusible disconnect providing short circuit protection and soft starting in one package.

Starter Kit for 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 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.


Learn how to prevent pump downtime

Get the latest information around pump motor maintenance! A  new podcast from Pumps & Systems magazine featured Jake Middleton and Dan Loflin from Siemens Industrial Controls business segment, click here & listen to the latest news: