Dynamo-electric principle

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The dynamo-electric principle states that an electric generator does not need an externally supplied electric current for the initial excitation to generate electric voltage , but can generate it itself through the initially low residual magnetism in the electromagnetic excitation winding through electromagnetic induction . The initially very small current caused by this in turn increases the magnetism in the excitation winding progressively up to the maximum possible value at the magnetic saturation of the iron core. This operating principle is generally referred to as positive feedback .

Discovery story

Werner von Siemens is generally regarded as the discoverer of this phenomenon after giving the first scientific presentation of the dynamo-electric principle with his lecture at the Berlin Academy of Sciences on January 17, 1867. Even before Siemens (and practically at the same time as it did) there were other people who dealt with this topic and described the principle.

As early as 1851/53 , Ányos Jedlik had supplied the field magnets with the electricity generated by the machine itself and described this, but made no further practical use of it. In 1854 the Dane Søren Hjorth applied for a patent for a generator machine with “ feedback ”, which contained both permanent magnets and electromagnets; he was the first to find and exercise self-excitement.

At almost the same time as Werner von Siemens, Charles Wheatstone also discovered and published the dynamo-electric principle. Wheatstone's lecture at the Royal Academy on February 14, 1867 immediately followed William Siemens' contribution , who had presented the work of his brother Werner von Siemens.

Wheatstone dealt with the parallel connection of armature and field windings in contrast to the Siemens variant with a series connection . The Wheatstone version later proved to be more important, especially for power plant technology. Siemens recognized the great importance of the self-excitation of generators without dependence on external auxiliary companies with the words: "Technology is currently given the means to generate electric currents of unlimited strength in a cheap and convenient way wherever labor is available."

Individual evidence

  1. ^ Proceedings of the Royal Society of London. Vol. 37, 1884, p. VIII (obituary for William Siemens).
  2. ^ W. Siemens: About the conversion of labor into electricity without the use of permanent magnets . In: Annals of Physics . tape 206 , no. 2 , 1867, p. 332-335 , doi : 10.1002 / andp.18672060113 .
  3. ↑ a b The electrification of the world - Werner von Siemens and the dynamo-electric principle. Siemens Historical Institute, accessed June 17, 2019 .
  4. ↑ a b c d Deutsches Museum: Werner Siemens' dynamo machine, history of discovery
  5. ↑ patent GB2199 : An improved electromagnetic machine. Registered on October 14, 1985 . By: RA Robertson (ed.): Mechanics' Magazine . tape 62 . Robertson, Brooman, and Co., London 1855 ( full text in Google book search).
  6. ^ CW Siemens: On the conversion of dynamical into electrical force without the aid of permanent magnetism . In: Proceedings of the Royal Society of London . tape 15 , 1866, pp. 367–369 ( PDF [accessed June 27, 2016]).