<P> The birth of the first transformer </P> <P> The first demonstrative long distance (34 km, i.e. 21 mi) AC line was built for the 1884 International Exhibition of Turin, Italy . It was powered by a 2 - kV, 130 - Hz Siemens & Halske alternator and featured several Gaulard secondary generators with their primary windings connected in series, which fed incandescent lamps . The system proved the feasibility of AC electric power transmission on long distances . After this success, between 1884 and 1885, Hungarian engineers Zipernowsky, Bláthy, and Déri from the Ganz company in Budapest created the efficient "Z.B.D." closed - core coils, as well as the modern electric distribution system . The three had discovered that all former coreless or open - core devices were incapable of regulating voltage, and were therefore impractical . Their joint patent described two versions of a design with no poles: the "closed - core transformer" and the "shell - core transformer". Ottó Bláthy suggested the use of closed - cores, Károly Zipernowsky the use of shunt connections, and Miksa Déri performed the experiments . </P> <P> In the closed - core transformer the iron core is a closed ring around which the two coils are wound . In the shell type transformer, the windings are passed through the core . In both designs, the magnetic flux linking the primary and secondary windings travels almost entirely within the iron core, with no intentional path through air . The core consists of iron strands or sheets . These revolutionary design elements would finally make it technically and economically feasible to provide electric power for lighting in homes, businesses and public spaces . Zipernowsky, Bláthy and Déri also discovered the transformer formula, Vs / Vp = Ns / Np . Electrical and electronic systems the world over rely on the principles of the original Ganz transformers . The inventors are also credited with the first use of the word "transformer" to describe a device for altering the EMF of an electric current . </P> <P> A very first operative AC line was put into service in 1885 in via dei Cerchi, Rome, Italy, for public lighting . It was powered by two Siemens & Halske alternators rated 30 hp (22 kW), 2 kV at 120 Hz and used 200 series - connected Gaulard 2 - kV / 20 - V step - down transformers provided with a closed magnetic circuit, one for each lamp . Few months later it was followed by the first British AC system, which was put into service at the Grosvenor Gallery, London . It also featured Siemens alternators and 2.4 - kV / 100 - V step - down transformers, one per user, with shunt - connected primaries . </P>

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