What is an autotransformer?

An autotransformer is a type of transformer that alters voltage levels while utilizing a single winding that acts as both the primary and secondary coil. This design incorporates a common portion of the coil, which allows it to serve both functions of stepping up or stepping down voltage. The shared winding increases efficiency and reduces the amount of copper and core material required compared to traditional transformers that have distinct primary and secondary windings.

The ability to adjust voltage levels efficiently makes autotransformers ideal for applications such as voltage regulation and in scenarios where space and weight savings are necessary. This characteristic distinguishes autotransformers from other types of transformers where separate coils are necessary for the two voltage levels, as well as from other electrical components such as rectifiers and capacitors, which serve different purposes in circuits.