VARIABLE AUTO TRANSFORMER

As with two winding Transformer, auto Transformers may be equipped with many taps and automatic switchgear to allow them to act as automatic voltage regulators, to maintain a steady voltage at the customers service during a wide range of load conditions.

By exposing part of the winding coils and making the secondary connection through a sliding brush, a contiguously variable turns ratio can be obtained, allowing for very smooth control of voltage. Applicable only for relatively low voltage designs, this device is known as a variable AC Transformer