Warren, Henry Ellis

SUBJECT AREA: Horology

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b. 21 May 1872 Boston, Massachusetts, USA

d. 21 September 1957 Ashland, Massachusetts, USA

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American electrical engineer who invented the mains electric synchronous clock.

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Warren studied electrical engineering at the Boston Institute of Technology (later to become the Massachusetts Institute of Technology) and graduated in 1894. In 1912 he formed the Warren Electric Clock Company to make a battery-powered clock that he had patented a few years earlier. The name was changed to the Warren Telechron (time at a distance) Company after he had started to produce synchronous clocks.

In 1840 Charles Wheatstone had produced an electric master clock that produced an alternating current with a frequency of one cycle per second and which was used to drive slave dials. This system was not successful, but when Ferranti introduced the first alternating current power generator at Deptford in 1895 Hope-Jones saw in it a means of distributing time. This did not materialize immediately because the power generators did not control the frequency of the current with sufficient accuracy, and a reliable motor whose speed was related to this frequency was not available. In 1916 Warren solved both problems: he produced a reliable self-starting synchronous electric motor and he also made a master clock which could be used at the power station to control accurately the frequency of the supply. Initially the power-generating companies were reluctant to support the synchronous clock because it imposed a liability to control the frequency of the supply and the gain was likely to be small because it was very frugal in its use of power. However, with the advent of the grid system, when several generators were connected together, it became imperative to control the frequency; it was realized that although the power consumption of individual clocks was small, collectively it could be significant as they ran continuously. By the end of the 1930s more than half the clocks sold in the USA were of the synchronous type. The Warren synchronous clock was introduced into Great Britain in 1927, following the setting up of a grid system by the Electricity Commission.

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Principal Honours and Distinctions

Franklin Institute John Price Wetherill Medal. American Institute of Electrical Engineers Lamme Medal.

Bibliography

The patents for the synchronous motor are US patent nos. 1,283,432, 1,283,433 and 1,283,435, and those for the master clock are 1,283,431, 1,409,502 and 1,502,493 of 29 October 1918 onwards.

1919, "Utilising the time characteristics of alternating current", Transactions of the American Institute of Electrical Engineers 38:767–81 (Warren's first description of his system).

Further Reading

J.M.Anderson, 1991, "Henry Ellis Warren and his master clocks", National Association of Watch and Clock Collectors Bulletin 33:375–95 (provides biographical and technical details).

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