GB140853A - Improvements in or relating to apparatus for converting alternating electric currents to direct currents and ???? ????? - Google Patents

Abstract

140,853. Calverley, J. E., and Highfield, W. E. Nov. 29, 1918. Commutator switching-arrangements; phase, changing.-Polyphase currents are converted to direct currents, or vice versa, by a collection of transformers with windings on the direct-current side connected to a commutator, while on the alternating-current side the windings are in two groups. In one group, each transformer has windings connected in two phases, and in the other group each transformer has a winding in one phase only or a combination of windings to produce an equivalent phase effect. The connexions of six transformers for converting from three-phase current to direct current are shown in Fig. 5. The transformers B, D, Fare energized by single coils included in the phase leads Y, X, Z respectively. The other transformers A, E, C have two coils each connected in series with the coil on the adjacent transformer. Each transformer has two secondaries 1, 1<A> - - 6, 6<A>, the coils being connected in the order 1, 2, 3, &c., 1<A>, 2<A>, 3<A>, &c. to the segments a - - l of the commutator. Direct current is taken off by brushes W which are rotated by a synchronous motor connected to the supply, and the motor may be over-excited to correct for the magnetizing-currents of the transformer. The six transformers shown may be replaced by two threephase transformers, the cores of one carrying primary coils separately connected in each of the phases, and the cores of the other carrying two coils connected in different phases. Additional transformers or cores carrying two coils may be used to provide more intermediate steps between the main phases. Direct current may be converted to alternating current and then back to direct current of a different voltage.