Transformer basics

A transformer is a device that transfers electrical energy from one circuit to another by magnetic coupling without requiring relative motion between its parts. It usually comprises two or more coupled windings, and, in most cases, a core to concentrate magnetic flux. An alternating voltage applied to one winding creates a time-varying magnetic flux in the core, which induces a voltage in the other windings. Varying the relative number of turns between primary and secondary windings determines the ratio of the input and output voltages, thus transforming the voltage by stepping it up or down between circuits. The transformer principle was demonstrated in 1831 by Faraday, though practical design did not appear until the 1880s.Within less than a decade, the transformer was instrumental during the "War of current" in seeing alternating current systems triumph over their direct current counterparts, a position in which they have remained dominant. By transforming electrical power to a high voltage, low current form and back again, the transformer greatly reduces energy losses and so enables the economic transmission of power over long distances. It has thus shaped the electricity supply industry, permitting generation to be located remotely from points of demand. Amongst the simplest of electrical machines, the transformer is also one of the most efficient, with large units attaining performances in excess of 99.75%. Transformers come in range of sizes from a thumbnail- sized coupling transformer hidden inside a stage microphone to huge giga VA-rated units used to interconnect portions of national power grids. All operate with the same basic principles and with many similarities in their parts, though a variety of transformer designs exist to perform specialized roles throughout home and industry.