Soft starter of squirrel cage rotor Induction motor.

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.

Soft starter is a better starter for starting of squirrel cage rotor induction motor. It is directly controlled by microprocessor based logic control and power electronics based power supply.

How soft starter works & why its best than other starter

Soft starter is better than any other starting method of squirrel cage rotor Induction motor as it controls the starting electronically during the whole time. In case of Star-delta starter or auto transformer starter we have only two step of operation. First is the reduced voltage reasonably choosed for a specific motor and the motor is let start in that voltage. After a certain time delay, the shifting to normal voltage is done. So there is no real time control in these starting method.

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.

Soft starter of Squirrel Cage rotor induction motor
Soft starter of Squirrel Cage rotor induction motor

comparison between soft starter , star delta and direct online starting
Comparison between soft starter , star delta and direct online starting

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