GB520739A - Improvements in or relating to polyphase electric transformers - Google Patents

Abstract

520,739. Phase changing. PATENTVERWERTUNGS-GES. HERMES. Oct. 29, 1938, No. 31350. Convention date, Oct. 30, 1937, [Class, 38 (ii)] In an arrangement of polyphase transformers for increasing the number of phases, for example for feeding a 24-phase rectifier, the windings of the two transformers E, F, Fig. 4, forming the polyphase system are so arranged that at least two of the secondary voltages following one another in phase sequence are obtained from the same transformer. The transformers E, F have star and delta connected primary windings respectively and the zig-zag connected secondary windings of each comprise 12-phase arrangements each formed of two 6-phase systems differing in phase by 15 degrees so that the secondary voltages shown in Fig. 3 are obtained. In another arrangement the secondary windings of the transformers G, H, Fig. 5, having star and delta connected primaries respectively, are formed of systems of 6-phase windings without zig-zag connections. Phase displacement of the voltages of the individual secondary windings is then obtained by adding thereto voltages in quadrature derived from separate transformers K, L. The primary windings of the transformers K, L, may be energized by connection to either the primary or secondary windings of the associated main transformers G, H.