What are the advantages of star-delta starter with induction motor?

The main advantage of using the star delta starter is reduction of current during the starting of the motor.Starting current is reduced to 3-4 times Of current of Direct online starting. Hence the starting current is reduced , the voltage drops during the starting of motor in systems are reduced.

1. The main advantage of using the star delta starter is 
reduction of current during the starting of the 
motor.Starting current is reduced to 3-4 times Of current 
of Direcr online starting.

2. Hence the starting current is reduced , the voltage 
drops during the starting of motor in systems are reduced.

At the time of starting an Induction motor tends to draw high-current (7to8 times higher than rated current ) . In small motors (<5hp) it’s okay. But for larger motor the starting current may be so high that it may damage the stator coil or even the power cables.
Star-Delta starter is used to reduce the starting current . Initially the motor windings are connected in star pattern. Then after a preset time the contactors make a delta pattern and the motor runs. While connected in star pattern, voltage across the stator coils is equal to the phase voltage (line voltage /1.3 aprox), so the value of starting current is reduced.