thyratron tube, type KU-676
Date: 1920-1940
Inventory Number: 2008-1-0076
Classification: Rectifier
Subject:
Maker: Westinghouse Electric & Manufacturing Company (1886 - 1945)
Maker: National Company, Inc. (1914 - 1970s)
Cultural Region:
Place of Origin:
Dimensions:
30 x 9.3 cm (11 13/16 x 3 11/16 in.)
Description:
A single bulb with four-prong plug base (silver on sides, white on bottom) and a white ceramic connector (with short length of wire terminating in a small fork connector) atop a silver metal cap at top end. Only three of the four prongs actually connect to components. There is another tiny prong, like a snap closure on a piece of clothing but slightly longer, which ends from the side of the base opposite the orange identifying sticker. Inside glass is mottled with dried silvery residue. Inside, its elements look like those of a triode, with cathode filaments, an anode plate, and a grid between them.
Signedon orange sticker on side of metal base: WESTINGHOUSE / THYRATRON TYPE / TYPE KU-676
FunctionThyratron are rectifiers based on a design similar to a triode vacuum tube, but which work with a rarefied atmosphere of noble gases, mercury vapor or hydrogen. As a triode amplifier, it has a heated cathode, an anode or plate, and a control grid.
In the case of thyratrons, when the voltage between the hot cathode and the anode is positive, and the grid is also positive with respect to the cathode, the gas in the bulb ionizes and an electric arc extends from the cathode to the anode transmitting current. When the grid is at the same or lower voltage than the cathode, the electric fields are not strong enough to ionize the gas and there is very little current flow. However, once an electric arc is established, even if the grid voltage is lowered, current will continue to flow until the voltage between cathode and anode is lowered (for this reason they cannot be used as amplifiers).
In the case of thyratrons, when the voltage between the hot cathode and the anode is positive, and the grid is also positive with respect to the cathode, the gas in the bulb ionizes and an electric arc extends from the cathode to the anode transmitting current. When the grid is at the same or lower voltage than the cathode, the electric fields are not strong enough to ionize the gas and there is very little current flow. However, once an electric arc is established, even if the grid voltage is lowered, current will continue to flow until the voltage between cathode and anode is lowered (for this reason they cannot be used as amplifiers).