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A transformer is an electrical devices that designed to convert alternating current from one voltage to another.
It can be designed to step down or step up voltages and works on the magnetic induction principle. There is no rotating parts and is a completely static solid static device, which insures, under normal operating conditions, a long and trouble-free life.
It consists, in its simplest form, of two or more coils of insulated wire wound on a laminated steel core. When voltage is given to one coil, called the primary, it magnetizes the iron core and voltage is then induced in the other coil, called the secondary or output coil.
The change of voltage (or voltage ratio) between the primary and secondary depends on the turns ratio of the two coils