Soft start and soft stop

KIMO Tabelle

Soft start and soft stop – Overview

What is a soft starter?

A soft starter is an electronic motor control device for the soft start and stop of three-phase induction motors.

The motor voltage is adjusted with a phase control by a ramp function. The supply frequency of the motor remains identical to the mains frequency.

With soft starting, the initial voltage (= starting torque) and the voltage rise (= acceleration) are adjustable.

During soft stop, the voltage is reduced with a ramp function.

   All KIMO® soft starter (soft start & soft stop) in an overview

KIMO Fig. Drehzahlregelung am Beispiel der Lüftertechnik


Soft start and soft stop devices are used wherever motors – as mentioned above – need to be started or slowed down gently. Pumps and conveyor belts are perhaps obvious examples.

However, the following articles also show other areas of application:

KIMO Sanftanlaufgerät SoftCompact

Start attentuation (AM) and soft starters (SM, SM2)
0.5 – 7.5 kW

SoftCompact® AM, SM


  • 1- or 2-phase controlled
  • AM : Start attenuation with bridging relay
    SM : Soft start with bridging relay for single-phase capacitor motors
    SM2 : Soft start with bridging relay and soft stop
  • Switch-on torque and run-up voltage ramp separately adjustable
  • Module housing for mounting on 35 mm DIN rails. Very compact version with a width of 45 mm.
  • With integrated bridging contactor
  • Easily retrofitted
  • Can be used as a combined soft-start and injection brake using the electronic brake modules LEKTROMIK B1


  • Conveyor belts
  • Packing equipment
  • Long-travel drives for cranes
  • Compressors
  • Heat pumps
  • Vibration transporters
  • Machines with gearbox, belt or chain drives
  • Special version for pole-change motors

   Show SoftCompact® AM (Start attentuation), SoftCompact® SM (Soft starters) details


Soft start and soft stop
4 – 2000 kW



  • 3-phase control
  • Wide voltage range 3AC 110 – 500 V or 3AC 220 – 690 V
  • Ramp-up time, ramp-down time and starting torque adjustable
  • Ramp-up times up to 100 s possible
  • Can be combined with electronic DC injection brakes
  • Current limit and upgrading with special functions
  • Control of external bridging contactor
  • Can be used as voltage controller
  • S2: Option I2 integrated
  • SD2: “Delta” connection (6 motor cables)


  • Pumps
  • Fans and compressors
  • Refrigeration compressors
  • Conveyor belts
  • Grinding machines
  • Saws
  • High speed and high load belts
  • Drives with pole-change motors
  • Machines with gearbox, belt or chain drives
  • Centrifuges

   Show LEKTROMIK® S2, SD2 details