Thomson DC Generator

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This model of a direct-current generator was designed by Elihu Thomson to produce a constant voltage. It could also be used as a motor that would maintain a constant speed. It came to the Smithsonian from the U. S. Patent Office, representing patent number 333,573, issued to Thomson on January 5, 1886. The patent itself indicates that no model was submitted (which is not surprising since by that time models were not required), and this example was probably given to the Patent Office at a slightly later date for display purposes.
Thomson and Edwin Houston were school teachers in Philadelphia in the 1870s when they formed a partnership (the Thomson-Houston Company) to enter the new and competitive arc-lighting field. They produced a number of successful generators, motors, meters, and lighting devices. Most of their system employed alternating current, which was as good as direct current for lighting. With the development of the transformer in the mid-1880s, AC systems assumed added importance because electricity generated at a low voltage could now be converted to high voltage for more efficient transmission and then converted back to safer low voltage for use by consumers. But electro-chemical applications (like plating) required DC generators, and, until the invention of a practical AC motor by Nikola Tesla at the end of the 1880s, street railways depended on DC.
Thomson-Houston merged with Edison's company in 1892 to form General Electric.
Currently not on view
Date made
patent date
associated person
Thomson, Elihu
associated company
Thomson-Houston Electric Company
Thomson, Elihu
Place Made
United States: Pennsylvania, Philadelphia
overall: 10 1/2 in x 10 1/2 in; x 26.67 cm x 26.67 cm
ID Number
catalog number
patent number
accession number
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Work and Industry: Electricity
Energy & Power
Data Source
National Museum of American History


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