GB285909A - Vacuum switch for alternating currents - Google Patents

Abstract

285,909. Maschinenfabrik Oerlikon. Feb. 25, 1927, [Convention date]. Arc-rupturing devices. - Relates to vacuum valves which are arranged so that one valve is used for each semi-period of an alternating current, the switching on and off being dependent on the setting up or interruption of the valve excitation. For switching large currents, the disadvantage of having to provide large valves, with the resulting large heating losses, is removed by short-circuiting the valves during normal running by means of mechanical switches. The invention resides in the initiation of the starting-up; the excitation, and the interruption are dependent on the position of the mechanical switch, so that the interruption of the current by the latter cannot take place before valves have been started up and excited, and the excitation is only interrupted when arcing at the mechanical switch is no longer possible. The valves may be mercury vapour valves which may both be put in a single vacuum chamber, or several valves in cascade may be used. The valves have anodes 5, 6, mercury cathodes 7, 8, starting devices and exciters 9, 10, and exciting batteries 11, 12. The fixed and movable contacts 16, 17 of the mechanical switch normally complete the circuit, and mechanically coupled to 17 are movable contacts 29, 30 and a contact 18 engaging a fixed contact 19. In switching off, the contacts 18, 19 remain in engagement until contacts 29, 30 bridge their respective contacts 21, 22 to start up the valves, which now take current, and then contacts 18, 19 separate. Contacts 29, 30 interrupt the excitation when the separation of contacts 17. 18 is such as to preclude arcing. The valves first come into operation on switching in.