Star Delta Starter

Star Delta Starter Points : Star Delta Starter, Definition After D.O.L starting the next most common method is by the start-delta method. Motors started by a star -delta starter must have the leads of each phase winding brought out to the terminal connection box of the motor. In the start position the windings are connected in star (A connection of three windings made in such a manner that one end of each winding is connected together); in the running position they are reconnected in delta (A circuit formed by connecting three electrical devices in series to form a closed loop).

If the line voltage is 230 volts, the voltage across each winding is 133 Volts.

The voltage across each phase winding in the start position is 580% of line voltage with consequent reduction of starting current. The starting torque is also reduced to one third. Star delta starting is acceptable for the driven machine. It will be acceptable for centrifugal fans and pump. With centrifugal loads the motor can be accelerate to approximately 75% to 85% of full speed on the star connection and then switched must be connected in delta.