اتوترانسفورماتور

thumb|right|300px|Single-phase tapped autotransformer with an output voltage range of 40–115% of input In electrical engineering, an autotransformer is an electrical transformer with only one winding. The "auto" (Greek for "self") prefix refers to the single coil acting alone. In an autotransformer, portions of the same winding act as both the primary winding and secondary winding sides of the transformer. In contrast, an ordinary transformer has separate primary and secondary windings that are not connected by an electrically conductive path between them.