GB322107A - Improvements in and relating to electric transformers - Google Patents

Abstract

322,107. British Thomson-Houston Co., Ltd., and Read, J. C. Dec. 4, 1928. Vapour-apparatus, arrangements of.-In an arrangement for supplying mercury arc rectifiers with 12-phase current obtained from a transformer having a 3-phase primary 1 and twelve secondary phases obtained by phase combination from star-connected groups 2 - - 5 of secondaries, there are provided two sets of interphase transformers 6, 8 producing high impedance in the anode circuits to different sets of harmonics. The interphase transformers 6 connected between the star points of the secondaries and the negative side of the D.C. system produce high impedance to all harmonics in the anode currents that are multiples of three except those that are multiples of twelve, whilst the interphase transformers 8 connected in the anode leads from the secondary phases produce high impedance to harmonics that are multiples of four except those that are multiples of twelve. The twelve phases are lettered consecutively A to L in order of phase sequence, each leg of the core of interphase transformers 8 having four windings carrying phase currents 90‹ apart. In a modification in which two 6-phase star-connected secondary groups are employed instead of four 3-phase groups, the interphase transformer set connected between the star points and the negative side of the D.C. circuit provides impedance to all harmonics that are odd multiples of six, the inherphase transformer set in the anode leads providing impedance to harmonics that are multiples of four. Specifications 289,152, 301,569 and 301,767 are referred to.