In 1879, Siemens & Halske presented the first electric locomotive with a power of 2 kW at the Berlin trade fair.
Only in 1886, Werner Siemens built a generator without the use of permanent magnet, proving that the machine could self-excite. The first dynamo of Siemens had a power of approximately 30 watts and a rotation of 1200rpm. The machine did not only function as an electricity generator, but could also operate as a motor, provided a direct current was used.
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In 1887, Yugoslavian Nikola Tesla presented a prototype electric motor with a short-circuit rotor, but due to poor performance Westinghouse, the project’s owner, abandoned development research.
In 1889, the German engineer Dobrowolsky of the AEG firm in Berlin filed a patent application for the design of a three-phase cage rotor motor. This one presented 80W of power with an efficiency of 80%. The advantages of the AC electric motor for the DC motor were striking: simpler construction, quiet, less maintenance and high safety in operation. In 1891 Dobrowolsky developed the first series line of asynchronous motors in varying powers of 0.4 to 7.5kW.