Soft Starters – 3RW40


Equipped with modern, ergonomic user prompting the SIRIUS 3RW44 soft starters can be commissioned quickly and easily using a keypad and a menu-prompted, multi-line display with background lighting. The optimized motor ramp-up and ramp-down can be established quickly, easily and reliably by means of just a few settings with a selectable language.


Four-button operation and plain-text displays for each menu point guarantee full clarity at every moment of the parameterization and operation. During operation and when control voltage is applied, the front panel continuously presents measured values and operating values as well as warnings and fault messages. An external display and operator module can be connected by means of a connection cable to the soft starter, thus enabling active indications and the like to be read directly from the control cabinet door.

The SIRIUS 3RW44 soft starters are equipped with optimum functionality. An integral bypass contact system reduces the power loss of the soft starter during operation. This reliably prevents heating of the switchgear environment.

The SIRIUS 3RW44 soft starters have internal intrinsic device protection. This prevents thermal overloading of the power section’s thyristors, e.g. due to unacceptably high closing operations. Wiring outlay for installing an additional motor overload relay is no longer needed as the SIRIUS 3RW44 soft starters perform this function too. In addition, they offer adjustable trip classes and a thermistor motor protection function. As an option the thyristors can also be protected by SITOR semiconductor fuses from short-circuiting. And even inrush current peaks are reliably avoided thanks to adjustable current limiting.


As a further option the SIRIUS 3RW44 soft starters can be upgraded with a PROFIBUS DP or PROFINET module. Thanks to their communication capability and their programmable control inputs and relay outputs the SIRIUS 3RW44 soft starters can be very easily and quickly integrated in higher-level control system.

In addition, a creep speed function is available for positioning and setting jobs. With this function the motor can be controlled in both directions of rotation with reduced torque and an adjustable, low speed. On the other hand, the SIRIUS 3RW44 soft starters offer a new, combined DC braking function for the fast stopping of driving loads.


  • Soft starting with breakaway pulse, torque control or voltage ramp, adjustable torque or current limiting as well as any combination of these, depending on load type.
  • Integrated bypass contact system to minimize power loss.
  • Various setting options for the starting parameters such as starting torque, starting voltage, ramp-up and ramp-down time, and much more in three separate parameter sets.
  • Start-up detection.
  • Inside-delta circuit for savings in terms of size and equipment costs.
  • Various ramp-down modes selectable: free ramp-down, torque-controlled pump ramp-down, combined DC braking.
  • Solid-state motor overload and intrinsic device protection.
  • Thermistor motor protection.
  • Keypad with a menu-controlled, multi-line, graphic display with background lighting.
  • Interface for communication with the PC for more accurate setting of the parameters as well as for control and monitoring.
  • Simple adaptation to the motor feeder.
  • Simple mounting and start-up.
  • Display of operating states and fault messages.
  • Connection to PROFIBUS with optional PROFIBUS DP module.
  • External display and operator module
  • Mains voltages from 200 to 690V, 50 to 60Hz.
  • Applicable up to 60°C (derating from 40°C).