An Auto Transformer is a type of transformer that uses a single winding to perform both the functions of a primary and secondary winding. In an autotransformer, a portion of the winding is shared between the primary and secondary circuits, allowing for a smaller and more cost-effective design than a traditional two-winding transformer.

Auto Transformers are also able to provide greater flexibility in voltage regulation, as they can be designed to provide a range of voltage ratios. This makes them an ideal choice for applications where precise voltage regulation is required, such as in electrical distribution systems.

Overall, auto transformers are a versatile and cost-effective solution for many applications where voltage transformation is required. With their high efficiency, compact design, and flexibility in voltage regulation, they are an ideal choice for a wide range of electrical distribution and transmission systems.