What is an auto transformer?

An auto transformer is defined by its unique construction and operating principles, which involve a single continuous winding that serves as both the primary and secondary circuit. This configuration allows the transformer to step up or step down voltage levels while maintaining a direct electrical connection between the input and output, making it efficient for various applications.

The auto transformer operates under the principle of electromagnetic induction, where part of the winding is common to both the primary and secondary sides. This design results in reduced material costs, as it uses less copper and takes up less space compared to conventional transformers that have separate primary and secondary windings. The ability to deliver and supply power effectively through this single winding is what characterizes an auto transformer, allowing for reliable voltage regulation in electric circuits.

Understanding this feature is key to recognizing that other types of transformers, such as isolation transformers, require complete electrical separation between the input and output, which an auto transformer does not provide. Similarly, limitations on voltage operation or polarity conversion (AC to DC) do not apply to the core function of an auto transformer.