what is the function of 3 phase auto transformer?

A three-phase autotransformer serves to step up or step down voltage levels in three-phase electrical systems. It utilizes a single winding that acts as both the primary and secondary, allowing for efficient voltage transformation with reduced material costs and size. This type of transformer is commonly used in applications such as voltage regulation, motor starting, and power distribution, providing a compact solution for managing three-phase power systems.