THE ALTERNATING CURRENT SYSTEM
Finally, Tesla’s foreman took him to meet A. K. Brown, manager of Western Union Telegraph Co. With Brown’s help, Tesla Electric Co. was formed in April 1887. Tesla patented singlephase, two-phase, and three-phase AC systems, and two AC motors. In the first four years of 3 operation, he was granted 40 patents. The patents were processed quickly since there was nothing like them at the patent office. Both scientific and business interests took note of the patent office activity and Tesla was soon receiving invitations to lecture. He turned out to be a natural speaker.
George Westinghouse had more than 30 AC power systems in operation at the time (under a different patent) and was interested in Tesla’s motor. Westinghouse paid Tesla a visit at his lab. Tesla went to work for Westinghouse and moved to Pittsburgh. Tesla’s motors ran at 60 Hz AC and could not be adapted to the 133 Hz Westinghouse system. Westinghouse was forced to switch to 60 Hz and this has become the standard electrical power frequency in the U.S. After several months in Pittsburgh, Tesla returned to New York [2 p.40]. He became a U.S. citizen on July 30, 1891, a status which he valued above all scientific honors. In September 1891 he went to Paris to lecture at the International Exposition and also visited his family in Croatia.
Edison was outraged when he learned of Tesla’s alliance with Westinghouse. He issued propaganda about the dangers of AC current. Edison conducted weekly demonstrations in which dogs and cats were electrocuted. Through a third party, he bought rights to Tesla’s AC patents and worked a deal with New York prison authorities to carry out the first execution by electrocution on 8/6/1890. The convict failed to die after the first shock and the ordeal had to be repeated. It was reported as “an awful spectacle, far worse than hanging.”
George Westinghouse became worn down financially by Edison’s anti-alternating current initiatives. A major obstacle to the ability of Westinghouse to get new funding was his contract with Tesla to pay him $2.50 for each horsepower manufactured. George Westinghouse appealed to Tesla to relinquish his claim to the patents. Tesla, interested in seeing his inventions put to use, agreed and settled for a cash sum. Tesla proved to be quite a showman on the lecture circuit. He had glass tubes that glowed without electrical connections. This was the forerunner of the florescent bulb, another invention
he didn’t bother to patent. He wore insulated shoes and allowed high-voltage, high-frequency electric current to flow across his body. His purpose in oing this was, in part, to counter 4 Edison’s propaganda about the danger of AC current. At high frequencies and voltages, electricity would run across the surface of the skin without penetrating. He demonstrated a motor run on one wire, with the return path through air. He spoke of the possibility of
transmitting power long distances through the upper atmosphere. One dazzling display was his “carbon-button lamp,” a partially evacuated glass globe with a piece of carborundum in one end connected to a single wire terminal. When high-frequency current was applied, “The central ‘button’ of material electrostatically propelled the surrounding gas molecules toward the glass globe. They were then repelled back toward the button, striking it and heating it to incandescence.”
The bulb was 20 times as efficient as the Edison bulb. Since a technical language had not yet evolved to describe these phenomena, Tesla described them poetically. For example, a static discharge he called a brush or a luminous stream . George Westinghouse won the contract for electrifying the Chicago World’s Fair of 1893—the first electrical fair. He invited Tesla to speak. 25 million Americans visited the fair, which was one-third of the population at the time. Tesla had blown tubes to spell “Welcome Electricians,” as well as the names of many famous scientists. He dazzled audiences with numerous demonstrations of high frequency, high-voltage current.