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Selenium rectifier
Type of power rectifier / From Wikipedia, the free encyclopedia
A selenium rectifier is a type of metal rectifier, invented in 1933.[1] They were used in power supplies for electronic equipment and in high-current battery-charger applications until they were superseded by silicon diode rectifiers in the late 1960s. The arrival of the alternator in some automobiles was the result of compact, low-cost, high-current silicon rectifiers. These units were small enough to be inside the alternator case, unlike the selenium units that preceded silicon devices.
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The rectifying properties of selenium, amongst other semiconductors, were observed by Braun, Schuster and Siemens between 1874 and 1883.[2] The photoelectric and rectifying properties of selenium were also observed by Adams and Day in 1876[3] and C. E. Fitts around 1886, but practical rectifier devices were not manufactured routinely until the 1930s. Compared with the earlier copper-oxide rectifier, the selenium cell could withstand higher voltage, but at a lower current capacity per unit area.[4]