GB185801A - Transforming an alternating electric supply to a supply having a larger number of phases - Google Patents

Abstract

185,801. Stigant, S. A., and Johnson & Phillips, Ltd. May 12, 1921. Phase, changing; polyphase transformers. - A three-phase system is converted into a system in which the number of phases is a multiple of three by means of a transformer with star-connected primary windings, the secondary phases being obtained in part from windings energized from two different primary phases and connected in series, and in part from windings energized from a single primary phase. The arrangement of the secondary windings for obtaining nine phases is shown diagrammatically in Fig. 2. The phases 1, 4, 7 are obtained from windings a, b, c, each of which is energized from a single primary phase, while the remaining phases 2, 3, &c. are obtained from pairs of windings a<1>, c<2>; b<1>, c', &c. energized from two different primary phases. In a modification, eighteen secondary phases are obtained, six of them from single windings and the remaining twelve from pairs of windings. Fig. 12 shows the arrangement for obtaining 24 phases. A further multiplication may be obtained by connecting adjacent terminals of the secondary windings by conducting coils provided with tappings. An example of this arrangement is shown in Fig. 13, in which the three primary phases are first converted into twelve secondary phases 1, 4, 7, - - 34 with a common junction o<1>, and the terminals of these secondary phases are connected by coils r with tappings 2, 3, 5, 6 &c., giving finally thirty-six secondary phases from the three primary phases. The coils r may be placed at any position between the common junction o<1> and the extremities of the sectors o<1>1, o<1>4 &c. to give a desired secondary voltage.