US Patent: 382,280
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| Electrical Transmission of Power
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Patentee:
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| Nikola Tesla (exact or similar names) - New York, NY |
| Manufacturer: |
| Not known to have been produced |
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Patent Dates:
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| Applied: |
Oct. 12, 1887 |
| Granted: |
May 01, 1888 |
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Jeff Joslin
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Description: |
| The primary focus of this important patent is on two-phase electric motors (the use of the term "phase" post-dates this patent; the patent specification describes "coils" and "circuits" rather than "phases"). However, almost as an aside Tesla shows a motor arranged for three evenly-spaced phases (Figures 13 and 14 in the patent drawings). Tesla failed to realize two key advantages of the three phase version. First, the instantaneous power level fluctuated much less in the three-phase system than in the two-phase system. Second, it was possible to interconnect the three-phase coils in either delta or wye configurations which reduced the number of switches and wires. A three-phase motor ran so smoothly that there was no significant advantage to using more phases than that. And reducing the number of wires from four in two-phase to three in three-phase was of cardinal importance when using three phase to carry electrical power on transmission lines. This patent (and the related patent 382,279, 382,281 and 382,282) implies that Tesla was not yet thinking about issues related to long distance power transmission. Michael von Dolivo-Dobrowolsky would get their first; see, for example, patent 455,683.One key reason why Dolivo-Dobrowolsky has largely been forgotten in favor of Tesla is that in 1896 Tesla sold all the rights to his polyphase motors to Westinghouse, who cross-licensed them to General Electric. Together, Westinghouse and GE had a near-monopoly on polyphase motors and generators. Meanwhile, Tesla had become a cultural icon in somewhat the same way that Edison had and that Einstein would become a few decades later, and Westinghouse and GE both found it advantageous to promote their association with Tesla, which led to the down-playing of the role played by Dolivo-Dobrowolsky. Another side-effect of the Tesla/Dolivo-Dobrowolsky schism is that Tesla favored 60 Hertz systems which became the choice in North America, whereas Dolivo-Dobrowolsky favored 50 Hertz systems which became the choice in Europe where Dolivo-Dobrowolsky's employer, AEG, was the dominant supplier of electrical systems.Tesla undoubtedly deserves most of the credit for inventing three-phase induction motors and generators as seen in this patent as well as patents 382,279 and 382,281. However, Dolivo-Dobrowolsky deserves the primary credit for inventing the three-wire three-phase electrical distribution system (patent 422,746) and the squirrel-cage motor design (patent 456,804). |
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