652,036. Transformer arrangements. BRITISH THOMSON-HOUSTON CO., Ltd. July 30, 1947, No. 20660. Convention date, July 30, 1946. [Class 38 (iv)] [Also in Group XXXVII] A switching system for interconnecting the windings of a three-phase electrical apparatus such as a transformer having three windings per phase, utilizes a switching unit (see Group XXXVII), comprising a series-parallel switch and a star - delta switch. In Fig. 4, the phases A, B, C of a transformer are connected in parallel-delta by the switching unit whilst in Fig., 5 they are connected in series-star, though as the two switch shafts 22, 34 are operated independently the windings may be connected in series-delta and parallelstar. The series - parallel switch has six moving contact elements 18 mounted on the shaft 22 and in the position of Fig. 4 these elements interconnect the fixed contacts 2, 3, 5 of each set of fixed contacts 2 ... 5 to connect the windings of each phase in parallel. In the position of Fig. 5 the elements 18 interconnect the fixed contacts 3, 4 to connect the windings of each phase in series. The stardelta switch has three moving contact elements 30 mounted on the shaft 34 and in the delta position, Fig. 4, interconnects adjacent pairs of contacts 2. In the star position, Fig. 5, the contact elements 30 connect alternate contacts 2 to a neutral bar 26.