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Technical details

230-460 V, three-phase

Choose the right soft starter

Soft starter sizing guide.

Fairford divides applications into 4 classes, based on which to select the appropriate soft start for the application. The classes are as follows:

  • Easy Start (Trip Class 2) - 3x starter current for 5s
  • Standard Trip (Trip Class 10) - 3x start current for 23s / 3.5x start current for 17s
  • Medium Heavy Start (Trip Class 20) - 4x start current for 19s
  • Heavy Start (Trip Class 30) - 4x start current for 29s

Typical representatives of each class are:

  • Easy start: Compressors, mixers and conveyor belts that start unloaded (standard load is available if load is possible)
  • Standard start: Fans (low inertia), pumps, partial compressors,…
  • Moderate start-up: compressors, larger fans, heavy conveyor belts,…
  • Hard start: mills, crushers,…


After selecting the appropriate class, select soft start according to the motor power on the table below.


  • PFE-02: 4,9 A; 2,2 kW*
  • PFE-04: 6,5A; 3 kW*
  • PFE-06: 8,5A; 4 kW*
  • PFE-08: 11,5 A; 5,5 kW*
  • PFE-10: 15,5A; 7,5 kW*
  • PFE-12: 22A; 11 kW*
  • PFE-14: 29A; 15 kW*
  • PFE-16: 35A; 18,5 kW*
  • PFE-18: 41 A; 22 kW*

* Note: The maximum power rating of the soft-start engine is applicable to Trip Class 2. In the case of higher (heavier-start) mode, the data/maximum power is of the appropriate class. You can find the relevant information in Soft Starter sizing ugide.