Does Star Or Delta Draw More Current. The end of each coil is connected to the starting point of the other coil that means the opposite terminals of the coils are connected together. In star connection the line current is equal to the phase current whereas in delta connection the line current is equal to root three times of the phase current.
The motor will draw excessive current and overheat. This is a big advantage of a star delta starter as it typically has around 13 of the inrush current compared to a DOL starter. Firstly the stator winding is connected in star and then in Delta so that the starting line current of the motor is reduced to one-third as compared to the starting current with the windings connected in delta.
But torque is directly porpotional to square of the voltage so to have better performace of induction motor it needed to be connected in delta.
The third contactor is the star contactor and that only carries star current while the motor is connected in star. This is a big advantage of a star delta starter as it typically has around 13 of the inrush current compared to a DOL starter. If the changeover from star to delta takes place at too low a speed this can cause a current surge which rises almost as high as the corresponding DOL value. The star connection is mostly used to start larger motors and then switched to the delta configuration for normal running when the motor is up to speed.
