How it began
The Ganz Works in Budapest used induction coils in its alternating-current lighting systems from 1878. In the summer of 1884 Otto Blathy and Miksa Deri ran experiments at the factory. That autumn they and Karoly Zipernowsky concluded that open-core devices were impractical. Blathy proposed a closed iron core, Zipernowsky proposed connecting the devices in parallel, and Deri carried out the tests. The three filed patent applications between January and March 1885 and showed the system at the National Exhibition in Budapest that year. It is called the ZBD transformer after their initials. Blathy coined the word transformer.
Before it existed
Nicholas Callan of Maynooth College in Ireland invented the induction coil in 1836, and Pavel Yablochkov used induction coils in his lighting system in 1876. In 1882 Lucien Gaulard and John Dixon Gibbs built a 'secondary generator' with an open, straight iron core and connected the units in series. It was shown in Turin in 1884 but was inefficient.
How it works
A transformer passes electrical energy between two coils that sit close together without touching. A changing current in the first coil sets up a changing magnetic field that induces a voltage in the second, so voltage can be stepped up or down. In the ZBD design the copper windings were wound around a ring of iron wire, or enclosed by one, so the magnetic flux stayed almost entirely in the iron. Early in 1885 the three engineers also cut eddy current losses by laminating the core. The lamps and other loads were connected in parallel.
How it spread
In the United States, William Stanley, working for George Westinghouse, redesigned the transformer in 1885 with a core of stacked E-shaped plates, which was easier to wind by machine than the ring-shaped Ganz core. In 1886 he used step-up and step-down transformers to light downtown Great Barrington, Massachusetts, the first full alternating-current distribution system in that country.
What changed first
The new transformers were 3.4 times more efficient than the open-core devices of Gaulard and Gibbs. Closed cores made it technically and economically feasible to supply electric power for lighting from a distance at high voltage. On the advice of Galileo Ferraris, the Italian government ordered a Ganz system for Rome, installed in October 1886.
