Answer Posted / sayan
The pinciple of a star dela starting is based on the fact
of reduction of the starting current at the time of
starting of the motor. But there is always a surge of
current whenever there is a transition from star to delta.
This is essentially useful for the motors which are
connected to systems which are prone to have a voltage dip
at the starting of the motor.But the only disadvantage of a
star delta starter is that the starting torque reduces
appreciably during starting the motor in star.
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