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![[image of flower]](../../ima/flowXS_04.gif)
Electric Motors |
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Chronology
Note: AC = alternating current; DC = direct current. An electric motor transforms the electrical energy provided by an electricity generator through an electrical circuit (transmission line) into the mechanical energy of a rotating shaft. The shaft is geared to machinery that produce useful work, e.g., fans, washing machines, refrigerators, vacuum cleaners, lathes, pumps, etc. There are many kinds of motors in may sizes, but the main distinction are alternating current (AC) and direct current (DC) motors. In 1821(5?), Michael Faraday, a British scientist, demonstrates the principle of an electric motor. Singer 231. In 1832, a small model direct current generator is developed Hippolyte Pixii. E. M. Clarke produces the first commercial direct current generator in 1834. Its small amount of power can be used in laboratories only. Singer 179-180 In 1834, after watching electromagnets being used to separate iron ore in Ironville, NY in 1833, Thomas Davenport of Brandon, VT buys an electromagnet and made it into the first direct current motor, powered by batteries. He receives a patent for it in 1837 and uses it to run a small model locomotive. He attempts to sell his motors from New York City, but there is no use for such a motor at this time, since more reliable amounts of mechanical power are obtained from water turbines and steam engines. Katz n.p. Motors will not become practical until a practical generator of electricity is developed. In 1861, Antonio Pacinotti, a professor of physics at the U. of Bologna, demonstrates a machine with a ring winding armature, enabling it to work as a generator or a motor from a battery. It is described in an Italian journal in 1864. Singer 188 With practical commercial generation now available, motors can be developed commercially. In 1873, Gramme and Fontaine exhibit in Vienna a reversible combination of 2 Gramme direct current generators, one acting as a generator to run the other acting as a motor. Singer 231 In May, 1888, Nikola Tesla receives patents for the first polyphase alternating current induction motorSinger 231 that will become the standard for all alternating current motors. It is based on a rotating magnetic field that eliminates the need for commutators used to reverse the current direction. He sells his invention to the Westinghouse Corp. and becomes associated with that company. Before this invention, there was no satisfactory small motor. A duplicate of the generator could be run as a motor, but it was not self-starting and it required other equipment for bringing it up to speed and supplying exciting current. The synchronous motor could be used only for limited special work. Singer 173 |
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