SAN FRANCISCO saw the opening of the first central power station in 1879, supplying DC from two Brush dynamos to arc lamps for lighting the streets. Similar systems were soon installed all over the world. AC generators began to be used for the same purpose and the two varieties of electricity supply coexisted for a time, with the advantage perhaps lying with DC generation. The invention by Tesla of the induction motor in 1887 altered the balance decisively in favour of AC generation. However, the induction motor would not start with single-phase AC unless an auxiliary coil was used, and a polyphase supply was needed. Presently three-phase generators were installed when it became apparent that considerable savings in copper were to be had, compared to single or two-phase AC systems1. By 1896 the Westinghouse company in the USA had settled exclusively for the three-phase system, partly because it gave smoother motor operation, and very gradually DC systems lapsed into obsolescence.
Unable to display preview. Download preview PDF.