Nikola Tesla is an Croatian and American inventor. He was born in Smiljan, Croatia in July 10, 1856 and died in New York, January 7, 1943. He was born in the Lika district, but he worked almost all his life in the USA, where he made all his inventions. He attended high school in Gospić, then in Karlovac, where he graduated. He enrolled at the Technical College in Graz in 1875. The first year he received a scholarship from the Croatian Military Borderland, and the second year the scholarship was absent because the Military Borderland was abolished. In 1876 and 1878, he applied for a scholarship from Matica Srpska in Novi Sad, but he did not receive it. At the beginning of 1880, he went to Prague in order to continue his studies, but there is no information that he completed his studies at any university. In 1881, he worked in the Central Telegraph Office in Budapest, and then in the Telephone Exchange, where he made a number of technical improvements. In the fall of 1882, he got a job in Paris in Edison’s telephone branch. Already during his studies, he warned about the disadvantages of the direct current electric motor. In Budapest, he imagined the application of multiphase alternating currents to create a rotating magnetic field that would cause rotation in an electric motor. In an effort to develop the imagined system of alternating currents, he went to the USA in 1884, where, on the recommendation of the head of Edison’s representative office in Europe, he got a job in T. A. Edison`s team. There he presented his ideas about the production and more profitable transmission of alternating currents, but he was not understood.
In 1885, Tesla founded his own company “Tesla Electric Light and Manufacturing Company” in New York for the production of electric arc lights, and in 1887 the company “Tesla Electric Company” with a laboratory where he first constructed alternating current electric motors. In the fall of the same year, he applied for the first patents on the production and transmission of multiphase alternating currents and their application for efficient operation of alternating electric motors. With these inventions, he showed that for most applications alternating current is much more suitable than direct current.
In order to create a rotating magnetic field in an electric motor without the use of a commutator, he used several pairs of coils powered by alternating currents that were shifted in time, so they differed in phase. For this, he had to first construct a generator that produces multiphase current. At first it was only two currents, but later he developed systems with three, six and more phase-shifted currents. The entire system included a two-phase alternating current generator and a motor with two pairs of coils fed by such current. Tesla electric motors for alternating current (synchronous, asynchronous and spiral) are simple in construction, which means cheaper to manufacture and maintain than those for direct current. On May 16, 1888, he held a notable lecture at the American Institute of Electrical Engineers entitled “A New System of Alternating Current Motors and Transformers”. The American inventor and industrialist G. Westinghouse bought all the patents on alternating current from Tesla in 1888. Tesla continued to perform experiments in the field of high-frequency currents and their application for lighting. He gave a notable lecture on May 20, 1891 at Columbia University in New York under the title “Experiments with very high frequency currents and their application in artificial lighting”. All the world’s newspapers wrote about Tesla’s inventions, and Tesla gave lectures all over America and Europe. Almost everything he talked about was new, in every lecture he showed amazing, always different experiments. In Paris, he received news that his mother was dying, so he traveled to Gospić. On his way back, at the invitation of the mayor M. Amruš, he gave a lecture on May 24, 1892 in the City Hall in Zagreb. With that lecture, he raised the self-confidence of engineers in Croatia to a high level, so they built and put into operation a hydroelectric power plant for alternating current on the Krka River just a few months after the one on Niagara. Tesla’s system of multiphase electric currents and its electric lighting were demonstrated by the Westinghouse company at the World’s Fair in Chicago in 1893, and they proposed Tesla’s system of alternating currents for the power plant at Niagara Falls. The power plant was completed in 1896, and with it, the city of Buffalo, about 40 km away, was supplied with a high-voltage transmission line (the high voltage significantly reduced losses), and then also more distant cities. At the same time, several hundred small direct current power plants were deployed in New York. Due to high losses, this type of electricity could only be transmitted over a distance of up to 3 km. In a few years, Tesla’s system of multiphase alternating currents began to be used all over the world, and during more than a century, it has not fundamentally changed.
Further research led Tesla to the area of currents of even higher frequencies, at even higher voltages. Working with high-frequency currents, Tesla discovered, investigated and applied many previously unknown phenomena and thus founded new branches of electrical engineering. He also used high-frequency alternating currents for wireless transmission of signals and energy. He gave a lecture about this on February 24, 1894 at the Franklin Institute in Philadelphia, and on March 3 at a meeting of the Electric Lighting Association in St. Louis.
In 1895, a fire broke out in Tesla’s laboratory, which destroyed all devices, blueprints, archives and Tesla’s private belongings. In just one year, he built a new laboratory in which he achieved very high voltages and created very strong electric fields with a transformer with a very high transformation ratio (later called the Tesla transformer). In them, the electric discharges were violent, similar to lightning, and the luminous tubes glowed even though they were not connected to the lines. In his work with high-frequency currents, he established that even with high voltages, they are not dangerous for humans, and he predicted their use in treatment. Further research led Tesla to the idea that with the help of such powerful high-frequency electromagnetic fields, electricity could be transmitted over long distances without the use of electrical conductors. The first step towards this goal was the wireless transmission of signals over a distance. He invented radio communications and remote control. He made a model of a ship that he controlled wirelessly at a distance using electric signals, and showed it publicly in New York in 1898. At that time, other radio inventors were transmitting signals over a distance of only a few kilometers. In the basic patent that he applied for in 1897 and received in 1900, the explanation states that the devices will have other useful applications, such as signal transmission.
As his attention was primarily focused on the wireless transmission of electricity, in 1897 Tesla built a large transmitting and receiving station in a secluded area in Colorado Springs where he perfected systems for wireless transmission of signals and electricity using voltages of several million volts. In the case of wireless long-distance transmission of electricity, the main difficulty was, and still is, the low efficiency of the system. In 1901, he began building a large radio station on Long Island in New York for the envisioned world radio communication system. A 57 m high pole was built for the antenna, topped with a dome of wires, 20 m in diameter. With it, he wanted to wirelessly transmit signals and electricity that is available to everyone and free of charge. Due to investors’ lack of understanding for a system in which energy and signals would not be charged, construction was suspended in 1905, and out of fear that the antenna would not serve German spies, it was demolished in 1917 by mining. He wrote and published an autobiography entitled “My Inventions” in 1919, and in occasional interviews with journalists he presented his ideas, among them the dreamlike energy transfer called Tesla’s “death rays”. In the last decades of his life, famous but also forgotten, he contacted only a few people, and towards the end of his life only with his nephew Sava Kosanović. Tesla received many awards and honorary doctorates for his inventions. The Nobel Prize passed him by because he did not want to share it with Edison. Tesla’s high-frequency currents, Tesla’s transformer and the older electrotherapeutic procedure of teslinization are named after him. The greatest recognition of Tesla’s work was given at the 11th General Conference for Weights and Measures in 1960, when the name “tesla” was accepted for the unit of magnetic induction.
He registered hundreds of inventions, mostly in electrical engineering, 112 patents in the USA and almost as many in other countries, and many inventions remained only recorded in his diaries or professional journals. In experiments with lighting tubes filled with gas under low pressure or completely evacuated, which began to be widely used for lighting only in the second half of the 20th century. He was on the verge of inventing the electron tube, the cathode ray tube, the X-ray tube and the electron microscope. He was also engaged in research in mechanical engineering. In 1913, he patented a turbine with many thin discs and no blades (Tesla turbine). As he had no interest and time to deal with the development and adaptation of his inventions to the market, many who developed his inventions appropriated them. It wasn’t until 1943 that the US Supreme Court invalidated Marconi’s US radio patents because Tesla’s earlier patents already contained everything Marconi described.
Throughout his life, Tesla was emotionally tied to his homeland. He responded to the congratulatory message sent to him by Vlatko Maček for his 80th birthday with a statement that he was proud of the Serbian nationality and the Croatian homeland. In 1896 he was elected an honorary member of the Yugoslav Academy of Sciences and Arts in Zagreb, and in 1926 an honorary doctorate of the University of Zagreb. In Croatia, streets are named after Tesla in many cities, several schools, one polytechnic, the company „Ericsson Nikola Tesla“, the state prize for science, a state medal, in the Technical Museum in Zagreb there is a permanent demonstration cabinet of Tesla’s inventions. The Nikola Tesla Memorial Center is located in Smiljan. Tesla’s house of birth and numerous models of his inventions are located there. The figure of Nikola Tesla can be found on Croatian coins of 10, 20 and 50 euro cents. Encyclopaedia “Britannica” included him among the 10 most important people in world history.