To start the induction motor by connecting external rheostat to the stator winding.
In this method external resistances are connected in series with each phase of stator winding during starting. This causes voltage drop across the resistance so that voltage available across motor terminal is reduced and hence the starting current. The starting resistances are gradually cut out in steps from the stator circuit as the motor picks up speed. When the motor attends rated speed, the resistance set to zero value and full line voltage is applied to the motor.