GB216495A - Improvements in systems of electric distribution - Google Patents

Abstract

216,495. British Thomson-Houston Co., Ltd. (Assignees of Alexanderson, E. F. W.). May 22, 1923, [Convention date]. Vapour and vacuum apparatus, arrangements of; phase, changing.-In order to obtain alternating currents of sinusoidal wave form from direct current mains, the current is passed through a group of electron discharge valves connected to primaries of three-phase transformers, and the grids or other elements determining the conductivity of the valves are subjected to potential waves of rectangular form obtained from an auxiliary group of high-potential low-power valves. In the thermionic valve arrangement shown in Fig. 1, twelve valves 1 - - 12 feed two double star transformer primaries 15, 21 having secondaries 31, 32 so disposed as to recombine the twelve-phase impulses into three phases, and to eliminate harmonics in outgoing distribution lines 33, 34, 35. The auxiliary valves 42 - - 53 are fed from the same direct current mains and have their grids subjected to rectangular waves from adjustable tappings of a ring winding 59, a cross-ring winding 61, and a battery 63. A rotary converter 66 determines the frequency in the alternating current distribution mains. In a modified arrangement the auxiliary grid potentials are obtained from a common transformer having an extended delta primary and a starconnected secondary. In a further modification mercury vapour rectifiers are arranged to furnish rectangular potential waves for the grids of the valves 1 - - 12.