Autotransformer

A transformer is a device that transfers electricalwith only one winding. The auto- prefix refers to
energy from one circuit to another throughthe single coil rather than any automatic
inductively coupled conductors—themechanism. In an autotransformer a portion of
transformer's coils. A varying current in the firstthe same winding acts as part of both the
or primary winding creates a varying magneticprimary and secondary winding.
flux in the transformer's core, and thus a varyingThe winding has at least three taps where
magnetic field through the secondary winding. Thiselectrical connections are made. The voltage
varying magnetic field induces a varyingsource and the electrical load are each both
electromotive force (EMF) or "voltage" in theconnected to two taps with one tap at the end
secondary winding. This effect is called mutualof the winding being a common connection to
induction.both circuits. Each tap along the winding
A variety of types of electrical transformer arecorresponds to a different source or load voltage.
made for different purposes. Despite their designAutotransformers are frequently used in power
differences, the various types employ the sameapplications to interconnect systems operating at
basic principle as discovered in 1831 by Michaeldifferent voltage classes, for example 138 kV to
Faraday.66 kV for transmission. Another application is in
The different types of transformers includeindustry to adapt machinery built for 480 V
power transformers, instrument transformers,supplies to operate on a 600 V supply. They are
pulse transformers, RF transformers, audioalso often used for providing conversions
transformers, etc.between the two common domestic mains
An autotransformer is an electrical transformervoltage bands in the world (100-130 and 200-250).