GB178190A - Improvements in and connected with apparatus for converting and/or transforming electric currents - Google Patents

Abstract

178,190. Calverley, J. E., and Highfield, W. E. Jan. 8, 1921, Phase, changing.-In apparatus for changing the number of phases of a polyphase system, in which a large number of transformer cores is provided, some of which carry windings of more than one of the phases of the system having the smaller number of phases, the magnetic conditions in the various cores are balanced by providing on some or all of the cores supplementary coils connected in one or more closed circuits. In the arrangement shown, for converting from three to 36 phases, eighteen cores 1 - - 18 are provided on six polyphase transformers. Each phase of the three-phase system is wound on one core of the transformer 1, 7, 13 and on two cores of each of the other transformers, the connections for the phase A being shown in Fig. 1. Each core carries a pair of oppositely-connected secondary windings, the phase relations of the 36 secondary windings 1 - - 18, 1<A> - - 18A being shown in Fig. 2. The supplementary balancing coils are connected in three closed circuits x, y, z, Fig. 4, which are interconnected electrically and magnetically to form a symmetrical system. Each balance circuit comprises a. winding on a core of the transformer 1, 7, 13, and windings on four other transformers, the arrangement being such that the vector polygon representing the electromotive forces generated in the circuit under balanced conditions is of elongated form, having a long side corresponding to the winding on the transformer 1, 7, 13. Since this transformer has only one winding in each primary phase, the balance circuits are placed in direct relation with the primary phases, the windings on the transformer 1, 7, 13 being the principal factors in determining the phase and magnitudes of the electromotive forces in the balance circuit. The secondary windings may be connected in a closed ring connected to commutating gear as described in Specifications 140,853, 150,824, and 150,825.