An Autotransformer can be used for step up, step down and split phase output balancing purposes.
While the step up and step down functions are fairly straightforward, split phase output balancing may require some more attention.

Autotransformers are often used to step up or step down voltages in the 110-115- 120 volt range and voltages in the 220-230-240 volt range – for example. providing 120V (with taps) from 240V input, allowing equipment designed for 120 volts to be used with a 240 volt supply (as in using US electrical equipment with higher European voltages).