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