What is the key characteristic of an autotransformer?

The key characteristic of an autotransformer is that it has a single winding that serves multiple purposes. This design allows the winding to act as both the primary and secondary winding, where a portion of the coil is common to both. As a result, the autotransformer can provide different voltage levels through taps along the same winding. This unique construction contributes to its compact size and efficiency.

The single winding structure sets the autotransformer apart from traditional transformers, which utilize separate primary and secondary windings. Moreover, this design typically results in lower losses and improved efficiency compared to transformers with multiple windings, making autotransformers suitable for applications where size and weight are a consideration.