1990, Vincent Del Toro, Basic Electric Machines Chapter 2One 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.
