Star-Delta Starter

           The star delta starting is a very common type of starter and extensively used, compared to the other types of the starters.

This method used reduced supply voltage in starting. Figure(1)shows the connection of a 3phase induction motor with a star –delta starter The method achieved low starting current by first connecting the stator winding in star configuration, and then after the motor reaches a certain speed, throw switch changes the winding arrangements from star to delta configuration.

The voltage applied for star delta starter to the individual motor winding is therefore reduced by a factor of  1/√3 this connection amounts to approximately 30% of the delta values. The starting current is reduced to one third of the direct starting current.

Motor Starting Characteristics of Star-Delta Starter

• Available starting current: 33% Full Load Current
• Peak starting current: 1.3 to 2.6 Full Load Current
• Peak starting torque: 33% Full Load Torque

Advantages of Star-Delta starter

• The operation of the star-delta method is simple and rugged
• It is relatively cheap compared to other reduced voltage methods
• Good Torque/Current Performance
• It draws 2 times starting current of the full load ampere of the motor connected

Disadvantages of Star-Delta starter

• Low Starting Torque (Torque = (Square of Voltage) is also reduce
• Break In Supply – Possible Transients
• Six Terminal Motor Required (Delta Connected
• It requires 2 set of cables from starter to motor