Three-phase transformer for powering semiconductor bridge rectifiers

Each of the three-phase windings of the three-phase transformer comprises the same even number of parts (5, 6, 7, 8; 42, 43, 44, 45) for each phase. In the winding which is intended for connection to a supply source, its parts (5, 6, 7, 8) are parallel-connected in each phase. In the other winding, which is intended for connection to a rectifier, the phases (A, B, C) of one half of its parts (43 and 45) are connected in a delta configuration and the phases (A,B,C) of the other half of its parts (42,44) are connected in star. The delta and star connections of the phases (A, B, C) of the parts (42, 43, 44, 45) of the winding intended for connection to the rectifiers (49, 60, 70, 71) follow one another alternately. The power factor of a transformer of this type can be increased and the active material cost of manufacturing the same can be reduced. Furthermore, the magnetic stray field produced by the above-described arrangement of the winding parts and by the phase connection of these parts ensures an inductive commutating impedance which is less than the commutating impedance which is evident in transformers of current design.