File:Warren master clock.png

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Summary

Description
English: Electric utility master clock invented by Henry Ellis Warren in 1916 and manufactured by his company Warren Telechron. These were installed in the control rooms of U.S. electric generating plants and were the first device to precisely control the daily frequency of electric power grids. Warren promoted these to electric utilities in order to stabilize the power grid frequency to make the synchronous electric clocks his firm produced accurate. By 1935 Warren master clocks regulated over 95% of the electric power in the U.S.

The device consists of a precision pendulum clock with a low temperature coefficient invar pendulum rod, and a synchronous electric clock driven by the 60 Hz electric power from the plant. The pendulum clock turns a black hand on the center dial, and the electric clock turns a gold hand on the same dial. The plant operator would adjust the output power until the two hands turned in synchronism. If the gold hand fell behind, the operator would increase power so the generators turned slightly faster, increasing the frequency of the alternating current, causing the electric clock to run faster until the gold hand caught up to the black one. If the gold hand got ahead, he would reduce power. This kept the averaged frequency of the AC power at exactly 60 Hz. The result was that all synchronous clocks attached to the power grid would keep in step with the precision pendulum clock, which was accurate to within a few seconds per week.

Before the use of these clocks, utilities only kept their grid frequency accurate to within about ±2%, which resulted in unacceptable synchronous clock errors of 1/2 hour per day. The dry cell batteries visible at the bottom powered an eddy current coil under the pendulum through a rheostat which could be used to adjust the rate of the pendulum without stopping it. The master clock was periodically checked against radio time signals broadcast by the U.S. Naval Observatory in Washington.
Date
Source Downloaded 2012-08-12 from Henry E. Warren (May 7, 1919) 'Using the time characteristics of alternating current', Trans. of Amer. Inst. of Elec. Eng., Vol. 38, Part 1, p. 772, Plate 35, Fig. 3 on Google Books
Author Henry Ellis Warren

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current18:03, 25 July 2015Thumbnail for version as of 18:03, 25 July 2015376 × 837 (136 KB)CmdrjamesonCompressed with pngout. Reduced by 50kB (27% decrease).
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