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SH11 / SH21

Electronic softstarter with 3 to 85 A rated current for asynchronous motors Voltage ranges: 110 ... 480 V, 1~ and 3~ Power ranges: 0.75 ... 15 kW

BLEMO softstarter

SH11 / SH21

The universal softstarter
from BLEMO - a series of devices
from 0,75 to 15 kW



The soft starters of the SH11/21 series ensure jerk-free starting (SH11) or starting and stopping (SH21) of asynchronous motors. This avoids torque surges caused by the otherwise abrupt starting torque, current peaks during switch-on and voltage dips in the mains and reduces wear on the mechanical drive elements. The soft starters of the SH11 series for progressive start-up are used with single-phase and three-phase motors when jerk-free starting is required.
The SH21 series of soft starters for progressive acceleration and deceleration are used for controlling the starting torque, reducing the starting current and for controlled deceleration for single and three-phase motors. The soft starters are designed for a voltage range of 110 to 480 V and are therefore universally applicable.

Standard features

  • Operating status display with 2 LED's
  • Boosteingang at SH21
  • Logic output for "Run-up" signalling
  • no neutral conductor (Mp/N) required
  • simple installation, also retrofitting
  • Smooth start and stop of all machines
  • available for mains from 110 to 480 V
  • suitable for all winding circuits
  • suitable for V3-circuit
  • Top hat rail mounting
  • Control voltage only required for SH11

Operating principle

In contrast to electromechanical starters, the electronic starters of the SH11/SH21 series allow the starting torque and starting time to be adjusted. The soft starters are particularly suitable for conveyor belts, automatic doors, drag lifts, small gantry cranes, fans, pumps, refrigeration compressors, compressors and machines with high inertia and all machines with belt drive.

Functional description

In the soft starters of the SH11 series, the current is controlled in one phase, in SH21 in two phases, time-dependently by an increasing voltage ramp.
The starting torque can be adjusted via a potentiometer.
A second potentiometer is used to adjust the ramp-up time according to requirements.
In the SH21 units, the deceleration time can be adjusted via a third potentiometer. SH21 devices also have a relay output which indicates the status of the soft starter.
After the start-up a built-in bypass relay bypasses the electronics and the motor runs directly on the mains.


  • Small compressors, fans
  • conveyors, conveyor belts
  • Automatic doors
  • Car wash facilities

Your benefits

  • Simple cabling,
  • Quick configuration
  • Reduces machine wear
  • Minimizes the maintenance time

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