How many windings does an auto-transformer have?

An auto-transformer is characterized by having a unique winding structure compared to conventional transformers. It consists of a single winding that acts both as the primary and secondary winding. This means that part of the winding is shared for both voltage transformation processes, allowing it to operate efficiently at lower costs with less material than traditional transformers.

In a typical auto-transformer, the winding is tapped at various points to provide different output voltages, but it fundamentally remains one continuous winding. This design leverages the principle of transformer operation without the need for separate windings for primary and secondary functions. Thus, describing the auto-transformer as having one winding accurately captures the essence of its construction and function.