Economy winding

An autotransformer winding is a special winding arrangement in electrical transformers in which the primary and secondary windings are not completely separated from each other, but instead partially share the same winding. This design is characteristic of autotransformers.

By sharing a winding part, autotransformers can save material, which results in lower costs, smaller construction volume and higher efficiency. However, there is no galvanic isolation between input and output, which is why autotransformers are only used where this isolation is not required.

Economy windings are typically used to adapt voltages with a small difference, for example in power distribution or in starting transformers for electric motors.