GB295031A - Improvements in or relating to control systems for rectifiers and other high vacuum apparatus - Google Patents

Abstract

295,031. Metropolitan-Vickers Electrical Co., Ltd., (Assignees of Smede, L.). Aug. 6, 1927, [Covention date]. Vacuum tubes; Low-pressure metallic-vapour apparatus.-A vessel, such as a mercury-vapour rectifier, which is evacuated to a pressure of a few microns of mercury has a glow-discharge device mounted in or communicating with the vessel and provided with electrodes between which a discharge takes place only when the pressure within the vessel is within predetermined limits, the discharge device being connected with a relay controlling the main switch of the rectifier; a pressure-responsive device, such as a manometer gauge, is connected with the vessel and serves to open the main switch when the pressure in the vessel exceeds that at which the glow discharge can be maintained. As shown, the glow discharge device 13 has electrodes 17, 18 spaced by a tubular insulator 23 closely surrounding central projections 19, 20 on the electrodes. The electrode 18, which may be formed with the projection 20 separate from the remainder, extends into a pipe 14 leading to a mercury-vapour rectifier 4, and a tortuous channel connects the pipe 14 with the inside of the device. The device is connected with the secondary of a transformer the primary 29 of which is connected through the winding of a relay 40 of the wattmeter type with an alternating- current supply. When the pressure in the rectifier increases beyond the predetermined limit, a discharge passes in the device 13, and the relay 40 closes a contact 41 to energize the opening coil 10 of main switch 8 of the rectifier, and to energize the winding 42 of a relay so as to de-energize the closing coil 9 of the switch 8. The relay 40 may also trip the coil of a master controller, so that the rectifier cannot be started except by hand, or a manometer 47 may be provided which, at a pressure of one-half to one millimeter of mercury, completes the circuit between two columns of mercury so as to close the circuit of the relay 42. In the modification shown in Fig. 4, the discharge device consists of an electrode 60 surrounding a central electrode 61 which is enclosed in an insulating sleeve 62 and has a tip 63 of carbon or graphite.