US Patent: 422,746
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| Electric induction apparatus or transformer
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Patentee:
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| Michael von Dolivo-Dobrowolsky (exact or similar names) - Berlin, Germany |
| Manufacturer: |
| Not known to have been produced |
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Patent Dates:
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| Applied: |
Jan. 08, 1890 |
| Granted: |
Mar. 04, 1890 |
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Jeff Joslin
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Description: |
| Few have heard of the Russian-Polish inventor Michael von Dolivo-Dobrowolsky, which is a shame because he substantially invented three phase power. Nikola Tesla is almost always credited as the inventor; as can be seen in patent 382,280, Tesla was aware of the idea of three-phase motors, but he failed to appreciate the advantages of three phases over two.In the late 1880s Nikola Tesla and Italian professor Galileo Ferraris independently and simultaneously developed two-phase electric motors and generators where the two phases were 90 degrees apart. Tesla obtained a US patent whereas Ferraris did not not attempt to patent his invention. In May 1888 George Westinghouse paid Ferraris $1,000 for his idea, and only then learned that Tesla held the patent rights. He ultimately paid Tesla $170,000 for those rights. Subsequent work in Westinghouse's laboratories, under the direction of Tesla, failed to produce a working system that would be viable at large enough scale. Part of the challenge is that Westinghouse employee Oliver Shallenberger had developed an electricity meter that worked at 133 cycles per second and so Westinghouse wanted the two phase electric system to work at that same speed. Tesla's original design used a 60 cycle system. Meanwhile, von Dolivo-Dobrowolsky noted that the instantaneous power in Ferraris'/Tesla's two-phase system fluctuated by 40 percent, whereas a three-phase arrangement, with the phases 120 degrees part, would fluctuate by only 15 percent. Furthermore, where the two-phase system needed four wires for power transmission the three-phase system only needed three wires.This patent covers the generators and motors that create and use his three-phase power. Patent 456,804 covers the squirrel-cage induction motor again (again, often mis-attributed to Tesla). Patent 455,683 covered the three-wire distribution system where the three phases are interconnected in either a Delta or Wye configuration. |
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