What is true regarding the operation of an autotransformer?

An autotransformer is a type of transformer that has a single continuous winding, which serves as both the primary and secondary winding, depending on the voltage transformation ratio required. In this configuration, the entire winding performs the role of the primary winding, while a portion of that winding acts as the secondary. This dual functionality is what differentiates autotransformers from traditional transformers that use separate windings for primary and secondary functions.

The ability of an autotransformer to step up or step down voltage is governed by how the taps are connected along the winding, but fundamentally, it is the same winding that fulfills both roles, making it more efficient for certain applications. This efficiency arises because a portion of the winding is used for both input and output, resulting in less copper use and lower losses.

In contrast, traditional transformers have distinct primary and secondary windings, and they rely on magnetic coupling between these separate windings to operate. Consequently, they do not exhibit the same operational characteristics or efficiency as autotransformers.

This characteristic of the autotransformer enables it to be both versatile and compact, but it also means that care must be taken in applications where voltage isolation is critical because there is less electrical isolation than with conventional transformers.