Advantages of Autotransformer :-

• Less Costly

• Better regulation

• Low losses as compared to ordinary two winding transformer of the same rating.

• It has a smaller size than an ordinary transformer of the same rating.

• It requires a smaller exciting current than a 2-winding transformer of the same rating.

• It required less Copper than an ordinary transformer of a similar rating.

• It has better voltage regulation and operates at a higher efficiency than a 2-winding transformer of the same rating.

Limitation of Autotransformer :-

• An auto transformer should not be used for interconnecting high voltage and low voltage systems.

• Used only in the limited places where a slight variation of the output voltage from input voltage is required.

• There is a direct connection between the primary winding and the secondary. Therefore, the output is no longer directly isolated from the input.

• The short-circuit current is much larger than for the two-winding transformer of the same rating.

• It is not safe for stepping down a high voltage to a low voltage. in case an open circuit develops in a common part of winding then full primary voltage appears across the load, it will dangerous to both people and equipment.