It can be stated that autotransformers are widely employed in electrical devices, such as elevators or downspouts, which vary between voltages in the range 110-117-120 volts and voltages in the 220-230-240 volts range. Thus 110 or 120V output from a 230V input can allow 100 or 120V elements to be put into use in a 230V region. The autotransformer winding has approximately three outputs, in which the electrical connections are made properly. A variable autotransformer is generated as the coil parts of the winding are exposed, producing the secondary connection by sliding a contact, resulting in a variation in the turns ratio.
An autotransformer may have some advantages, such as being smaller in size, lighter in weight, and more economical than a standard dual winding transformer. However, the autotransformer can not provide adequate electrical insulation. Transformers are determined according to numerous factors. Classifications are predetermined according to different criteria, such as the purpose of each device, as well as the type, number of phases and core material, for example.