Soft starter is an electronic controlled starting of squirrel cage rotor induction motor to avoid high inrush of starting current in DOL – direct online starter and excessive electrodynamic stresses due to change over in that case of STAR-DELTA starter and Auto transformer stating of squirrel cage rotor induction motor.
How soft starter works & why its best than other starter
On the other hand soft starter has direct control during the whole starting process. Soft starter constitutes by two part. One is control and another is power. The power unit constitutes of power electronics like thyristor and control unit has processor based micro logic. Now in soft starter there is no sudden shift, the starting current limit, starting time, torque could be adjusted by the control system of soft starter.
The starting phase typically occurs with KL closed and KB open so that the soft starter can control starting; afterwards, KB is closed with the exclusion of the power unit inside the soft starter whereas the control unit is left active.