War of the currents

The war of the currents (also known battle of the currents) was a series of events surrounding the introduction of competing electric power transmission systems from 1880's to early 1890's. It included commercial competition, a debate over electrical safety, and a media campaign that grew out of it, with the main players being the direct current (DC)–based Edison Electric Light Company and the alternating current (AC)–based Westinghouse Electric company. It took place during the introduction and rapid expansion of the alternating current standard.

The introduction of large scale outdoor arc lighting systems in the mid- to late-1870's, some of them powered by high-voltage alternating current, was followed in 1882 by Thomas Edison's low voltage DC electric distribution devices designed for indoor business and residential use as an alternative to gas and oil-based lighting. In 1886 George Westinghouse began building an alternating current system based on Nikola Tesla's patented idea of AC electricity that used a transformer to step up voltage for long-distance transmission and then stepped it back down for indoor lighting, a more efficient and less expensive system that directly competed for the market the Edison system was designed to serve. As many other electric companies joined in and the use of AC spread rapidly, Edison's company made claims in early 1888 that alternating current was hazardous and inferior to the patented direct current system.

Westinghouse Electric's advertisement catalog from 1880.

There were several technical factors that drove the adoption of alternating-current over direct-current. The direct-current system generated and distributed electrical power at the same voltage as used by the customer's lamps and motors. This required the use of large, costly distribution wires and forced generating plants to be near the loads. With the development of a practical transformer, alternating-current power could be sent long distances over relatively small wires at a conveniently high voltage, then reduced in voltage to that used by a customer. Alternating-current generating stations could be larger, more efficient, and the distribution wires were relatively less costly.

The lower cost of AC power distribution prevailed, though DC systems persisted in some urban areas throughout the 20th century. While DC power is not used generally for the transmission of energy from power plants into homes as Edison and others intended, it is still common when distances are small or when isolation between different AC systems is needed, known as High-Voltage DC (HVDC). Low voltage DC is used widely in modern electronic devices, including computers, telephones, and automotive systems; in contrast, most households and electric machines are powered by line voltage AC.

SOURCE : Wikipedia

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