Star/Delta starters are probably the most common reduced voltage starters. They are used in an attempt to reduce the start current applied to the motor during start as a means of reducing the disturbances and interference on the electrical supply.

Why we use soft starter instead of star delta starter?

Compared with star/delta starters, soft starters are much more flexible and provide a smooth start with no risk of transients. Star/delta starters offer limited performance because: Start torque cannot be adjusted to accommodate motor and load characteristics.

Why is the star delta starter preferred with induction motor?

Because of the reduction in starting current, starting torque reduces. Therefore we can conclude that by using Star Delta starter, the starting current is reduced to approximately two-thirds. Since starting current is reduced, the voltage drops during the starting of motor in systems are reduced.