autotranszformátor

An autotransformer is a type of electrical transformer that uses a single tapped winding instead of two or more separate windings, as is found in conventional transformers. This single winding acts as both the primary and secondary coil. The windings are electrically connected, and power is transferred through both electromagnetic induction and electrical conduction.

Autotransformers are commonly used for voltage regulation and for starting electric motors. Because they use less copper than conventional transformers of the same rating, they are often lighter and cheaper. However, they offer less electrical isolation between the primary and secondary circuits, which can be a disadvantage in some applications. The voltage transformation ratio is determined by the ratio of the number of turns in the winding. If the tap is placed at the midpoint, it can provide a 1:2 voltage ratio. If the tap is closer to one end, it can provide a higher or lower ratio.

A key characteristic of an autotransformer is that a portion of the winding carries both the primary and secondary current, while another portion only carries the difference between the two. This makes them more efficient than two-winding transformers for small voltage ratios. They are also useful when a small voltage adjustment is needed, such as in dimmer switches or variacs (variable autotransformers). Safety considerations are important due to the lack of isolation; if the primary winding fails, the secondary circuit may be directly connected to the full primary voltage.