Auto transformer starting is a method of starting a three-phase induction motor using an auto transformer. It is a type of reduced voltage starting method that reduces the voltage applied to the motor during the starting period. The auto transformer is a transformer that has a common winding, which serves as both the primary and secondary winding.
In auto transformer starting, the motor is connected to the auto transformer using a tap switch. During starting, the tap switch is set to a low voltage tap, which reduces the voltage applied to the motor. After the motor has reached a certain speed, the tap switch is moved to a higher voltage tap to provide full voltage to the motor. The auto transformer provides a smooth starting current, reducing the inrush current and the mechanical stresses on the motor.
The advantages of auto transformer starting are its low cost, reduced starting current, and reduced mechanical stresses on the motor. It is suitable for starting medium-sized and large induction motors that require a reduced voltage starting method. However, it can cause voltage dips and disturbances to other electrical equipment connected to the same supply. Additionally, it requires a larger physical space than DOL starting.
In summary, auto transformer starting is a method of starting a three-phase induction motor using an auto transformer. It is a type of reduced voltage starting method that reduces the voltage applied to the motor during the starting period. It is suitable for medium-sized and large induction motors that require a reduced voltage starting method. However, it can cause voltage dips and requires a larger physical space than DOL starting. It is important to consider the specific requirements of the motor and driven machinery when selecting the starting method.