Nikola Tesla and the AC Electrical System

Nikola Tesla (1856-1943) was the Serbian-American inventor, electrical engineer, and futurist whose work on alternating current (AC) power transmission and the AC motor laid the foundation for the modern electrical grid. Tesla’s inventions and ideas were central to the development of the electrical industry in the late nineteenth and early twentieth centuries, and they helped to win the famous “war of the currents” between the AC and DC systems.

Early Life and Education

Tesla was born in 1856 in the village of Smiljan, in the Croatian Military Frontier of the Austrian Empire (modern-day Croatia). His father was a Serbian Orthodox priest, and his mother, although unschooled, was a talented inventor of household devices. From an early age, Tesla showed a remarkable talent for mathematics and for visualizing machines in his mind. He later described how he could design and test machines entirely in his imagination, without ever building a physical prototype.

Tesla studied electrical engineering at the Austrian Polytechnic in Graz and at the University of Prague, but he did not complete a degree. In 1882, while walking in a park in Budapest, he had a sudden vision of the rotating magnetic field, the principle on which the AC motor is based. The vision was so clear that he later said he could see the entire motor in his mind, complete in every detail.

The AC Motor

Tesla moved to Paris in 1882, where he worked for the Continental Edison Company, the European subsidiary of Thomas Edison’s company. While in Paris, he began to develop the AC motor he had envisioned in Budapest. The key to the motor was the rotating magnetic field, which was produced by passing two or more alternating currents through coils of wire arranged around a central rotor. The rotor, in turn, rotated at a speed determined by the frequency of the AC current, without any physical contact between the rotor and the coils.

The AC motor had several advantages over the DC motor that was then in common use. It did not require a commutator, the device that switches the direction of the current in a DC motor, and which is a frequent source of failure. It was also more efficient, more reliable, and easier to maintain. Tesla applied for patents on his motor in 1887, and he sold the patent rights to George Westinghouse, the American industrialist who was developing an AC power system.

The War of the Currents

The late 1880s saw a famous conflict between the proponents of AC and DC electrical systems. The DC system, championed by Thomas Edison, was the older technology, and it was well established in the United States by the time Tesla and Westinghouse began promoting AC. The DC system, however, was limited in the distance it could transmit electricity, since DC loses voltage over long wires. The AC system, by contrast, could transmit electricity over much longer distances by using transformers to step up the voltage for transmission and then step it down for use by customers.

The war of the currents was both a technical and a business conflict. Edison fought the AC system fiercely, partly because his company had invested heavily in DC technology and partly because he personally believed that AC was dangerous. Edison was even involved in the development of the electric chair as a way of demonstrating the supposed dangers of AC.

The AC system eventually won the war, largely because of its technical superiority in long-distance transmission. The article on Thomas Edison and the electrical industry describes Edison’s role in this conflict in more detail. The victory of AC made possible the construction of large central power stations that could serve entire cities, and it laid the foundation for the modern electrical grid.

Tesla and Westinghouse

Tesla’s relationship with Westinghouse was both productive and disappointing. Westinghouse recognized the value of Tesla’s inventions and paid him a substantial sum for the patent rights, and he was a fair and generous employer. However, the financial difficulties that Westinghouse faced in the early 1890s led him to renegotiate his royalty agreement with Tesla, and Tesla gave up his royalties in exchange for a lump sum. This decision cost Tesla a fortune, since the AC system he had helped to develop became the standard for the entire electrical industry, and the royalties he had given up would have made him a very wealthy man.

Tesla’s relationship with Edison was also complicated. The two men were very different in temperament and approach, and they had a famous falling out over the merits of AC versus DC. The article on Thomas Edison and the electrical industry describes the rivalry in more detail. Despite their differences, both men were important figures in the development of the modern electrical industry.

Tesla’s Other Inventions

Tesla was a prolific inventor, and he held more than 300 patents around the world. His other inventions and ideas included:

The Tesla coil, a high-voltage, high-frequency transformer that is still used today in radio transmitters, televisions, and other electronic equipment.
Improvements to the wireless telegraph, which Tesla developed in the 1890s in competition with Guglielmo Marconi.
Early experiments with X-rays, which Tesla conducted around the same time as Wilhelm Röntgen.
Proposals for the wireless transmission of electricity, which Tesla believed could be used to transmit power over long distances without wires.
Early experiments with radio-controlled boats, which Tesla demonstrated at the 1898 Electrical Exhibition in New York.

Many of Tesla’s ideas were ahead of their time, and some have still not been fully realized. His proposal for the wireless transmission of electricity, in particular, has been the subject of renewed interest in recent years as a possible way to transmit electricity from solar collectors in space to receivers on Earth.

Tesla’s Later Life

Tesla’s later life was marked by financial difficulty and relative obscurity. He was a poor businessman, and he often failed to commercialize his inventions. He was also a controversial figure, with a reputation for eccentric behavior and for making grand claims that he could not always back up. In the early twentieth century, he was largely ignored by the mainstream scientific community, and he died in 1943 in relative poverty.

In recent years, Tesla has been rediscovered, and he is now widely celebrated as one of the great inventors of the modern age. The electric car company Tesla Motors, founded in 2003, was named in his honor, and the SI unit of magnetic flux density, the tesla, was named after him. Tesla’s later career stands as a cautionary example of how brilliant inventors can fail to commercialize their ideas, even when those ideas transform the world.

Tesla’s Legacy

Tesla’s most important legacy is the AC system of power generation, transmission, and distribution. The AC system, which Tesla and Westinghouse developed in the 1880s and 1890s, is the foundation of the modern electrical grid, and it is still in use around the world today. Without the AC system, the large central power stations that generate most of the world’s electricity would not be possible, and the wide distribution of electrical power that has transformed daily life would not have been achieved.

Tesla’s other legacy is the model of the research-based inventor-engineer. Tesla was not a pure scientist, and he was not a pure businessman, but he was a brilliant engineer who combined deep theoretical knowledge with practical skill. His career, like Edison’s, illustrates the new kind of industrial research that emerged in the late nineteenth century, with its combination of theoretical science, practical engineering, and commercial application.

The Continuing Question

The unresolved question about Tesla is how to separate his real contributions from the mythology that has built up around him. The traditional answer, going back to his own autobiographical statements and given its modern form in the popular “rediscovered genius” literature of the 1990s and 2000s, is that Tesla was a tragic and unappreciated genius whose AC system was stolen by Edison and Westinghouse, and who was the real inventor of radio (rather than Marconi), radar, and a long list of other modern technologies. The revisionist answer, developed in W. Bernard Carlson’s Tesla: Inventor of the Electrical Age (2013) and given its most detailed form in the work of electrical historian Thomas Hughes, is more sober: Tesla’s real contributions were the AC induction motor and the polyphase AC system, both developed in the 1880s and now the foundation of the modern electrical grid; his later claims about wireless power transmission, death rays, and other grand technologies were not backed up by working demonstrations and are best read as the products of a brilliant but increasingly isolated mind. The interesting current question, raised in the recent literature on the AC-vs-DC “war of currents” and in the work of business historian Alfred Chandler, is how to read the late-19th-century electrification of the United States and Europe: as a story of heroic individual inventors (Edison, Tesla, Westinghouse), or as a story of large-scale systems building (General Electric, AEG, the engineering of central power stations and long-distance transmission lines). The honest answer, given the historical evidence, is that both readings are needed, and that the systems-building story is the one that explains the rapid diffusion of the AC system in the 1890s and 1900s.

Selected Sources

W. Bernard Carlson, Tesla: Inventor of the Electrical Age (2013).
John Joseph Beer, The Emergence of the German Dye Industry to 1925 (1959).
Thomas P. Hughes, Networks of Power: Electrification in Western Society, 1880-1930 (1983).
Robert H. Wiebe, The Search for Order, 1877-1920 (1967).