autotransformer

auto- +‎ transformer

autotransformer (plural autotransformers)

1. (electrical engineering) A transformer with a single winding, its output being taken from taps.
   • 1990, Vincent Del Toro, chapter 2, in Basic Electric Machines, →ISBN, page 89:

     One of the principal features of the ordinary configurations of the transformer [...] is the electrical isolation that exists between the primary and secondary windings. [...] Whenever large transformation ratios are involved, safety demands that ordinary transformers be used. However, in instances where the transformation ratio is close to unity (which minimizes the hazard), a transformer employing a single tapped winding may be used with notable advantages.
     [...] This arrangement is called the autotransformer.

• balancing coil
• compensator