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Circuit Diagram and Working Principle of Star-Delta Starter
The figure shows the connection diagram of a 3-phase induction motor with a star-delta starter. The star-delta starter is a very common type of starter and is extensively used for starting the squirrel cage induction motors. It is used for starting a squirrel cage induction motor which is designed to run normally on delta connected stator winding.
When the switch S is in the START position, the stator windings are connected in star. When the motor attains a speed about 80 % of rated speed, then the changeover switch S is thrown to the RUN position which connects the stator windings in delta.

By connecting the stator windings, first in star and then in delta, the line current drawn by the motor at starting is reduced to one-third than the starting current with the windings connected in delta. At the time starting, when the stator windings are connected in star, then each phase gets a voltage equal to 𝑉𝐿/√3, where VL is the line voltage.

Since the torque developed by an induction motor is directly proportional to the square of the applied voltage, the star-delta starter reduces the starting torque to one-third as compared to the torque obtained with the direct-delta starting.

Theory of Star-Delta Starter
At starting, the stator windings are connected in star fashion, thus the voltage across each phase winding is

Circuit Diagram and Working Principle of Star-Delta Starter
The figure shows the connection diagram of a 3-phase induction motor with a star-delta starter. The star-delta starter is a very common type of starter and is extensively used for starting the squirrel cage induction motors. It is used for starting a squirrel cage induction motor which is designed to run normally on delta connected stator winding.
When the switch S is in the START position, the stator windings are connected in star. When the motor attains a speed about 80 % of rated speed, then the changeover switch S is thrown to the RUN position which connects the stator windings in delta.

By connecting the stator windings, first in star and then in delta, the line current drawn by the motor at starting is reduced to one-third than the starting current with the windings connected in delta. At the time starting, when the stator windings are connected in star, then each phase gets a voltage equal to 𝑉𝐿/√3, where VL is the line voltage.

Since the torque developed by an induction motor is directly proportional to the square of the applied voltage, the star-delta starter reduces the starting torque to one-third as compared to the torque obtained with the direct-delta starting.

Theory of Star-Delta Starter
At starting, the stator windings are connected in star fashion, thus the voltage across each phase winding is

Circuit Diagram and Working Principle of Star-Delta Starter
The figure shows the connection diagram of a 3-phase induction motor with a star-delta starter. The star-delta starter is a very common type of starter and is extensively used for starting the squirrel cage induction motors. It is used for starting a squirrel cage induction motor which is designed to run normally on delta connected stator winding.
When the switch S is in the START position, the stator windings are connected in star. When the motor attains a speed about 80 % of rated speed, then the changeover switch S is thrown to the RUN position which connects the stator windings in delta.

By connecting the stator windings, first in star and then in delta, the line current drawn by the motor at starting is reduced to one-third than the starting current with the windings connected in delta. At the time starting, when the stator windings are connected in star, then each phase gets a voltage equal to 𝑉𝐿/√3, where VL is the line voltage.

Since the torque developed by an induction motor is directly proportional to the square of the applied voltage, the star-delta starter reduces the starting torque to one-third as compared to the torque obtained with the direct-delta starting.

Theory of Star-Delta Starter
At starting, the stator windings are connected in star fashion, thus the voltage across each phase winding is

Circuit Diagram and Working Principle of Star-Delta Starter
The figure shows the connection diagram of a 3-phase induction motor with a star-delta starter. The star-delta starter is a very common type of starter and is extensively used for starting the squirrel cage induction motors. It is used for starting a squirrel cage induction motor which is designed to run normally on delta connected stator winding.
When the switch S is in the START position, the stator windings are connected in star. When the motor attains a speed about 80 % of rated speed, then the changeover switch S is thrown to the RUN position which connects the stator windings in delta.

By connecting the stator windings, first in star and then in delta, the line current drawn by the motor at starting is reduced to one-third than the starting current with the windings connected in delta. At the time starting, when the stator windings are connected in star, then each phase gets a voltage equal to 𝑉𝐿/√3, where VL is the line voltage.

Since the torque developed by an induction motor is directly proportional to the square of the applied voltage, the star-delta starter reduces the starting torque to one-third as compared to the torque obtained with the direct-delta starting.

Theory of Star-Delta Starter
At starting, the stator windings are connected in star fashion, thus the voltage across each phase winding is