autotransformaatit

Autotransformaatit, or autotransformers, are a type of transformer in which the primary and secondary circuits are connected to a single, continuous winding. The output voltage is derived from a tap on that winding rather than from an entirely separate coil. Because the same winding carries both voltages, the transformation involves a shared portion of turns.

Construction and operation: The winding has a primary section and a tapping point that provides the secondary terminal. When connected to a source, current flows through a portion of the winding that is common to both sides, and the output is taken between the tap and another end. The voltage ratio depends on the position of the tap. Autotransformers can be more compact and economical than two-winding transformers for modest voltage changes, but there is no galvanic isolation between primary and secondary.

Advantages and limitations: Benefits include lower material costs, smaller size, and high efficiency for relatively small voltage changes. They require less copper and core material than equivalent two-winding transformers. Limitations include lack of isolation, which means increased risk of shock and potential for shared fault paths. Also, insulation and protection schemes must be appropriate for the combined winding voltage and possible transient conditions.

Applications: Used in power distribution for voltage regulation and in equipment where only a small voltage adjustment is needed. Autotransformer starters are common for induction motors to limit starting current. They are also employed in voltage conversion for supplying equipment with slightly different nominal voltages, where isolation is not required.