User:John Symonds

Variable Transformers
A transformer is an electrical component which is used to convert ac voltage from one level to another, whereas variable transformers have the ability to vary the secondary (output) voltage. This is achieved by having a sliding or rolling electrical-carbon brush in contact with the windings which can be moved by using a control knob and scale or a servo-motor. For this reason, soon after ac electricity became widely available at the turn of the 19th century, they were used for regulating voltage in place of variable resistors which dissipated too much energy.Typical applications ranged from the dimming of theatre lighting to the speed control of electric train sets. Up until the introduction of industrial power electronics the variable transformer was used widely for many applications where voltage regulation was required, including motor speed control, electroplating, cathodic protection and laboratory applications.