GB635658A - Improvements in and relating to magnetic cores - Google Patents

Abstract

635,658. Transformers. BRITISH THOMSON-HOUSTON CO., Ltd. Jan. 16, 1948, No. 1447. Convention date, Jan. 18; 1947. [Class 38 (ii)] A magnetic core for 3-phase induction apparatus comprises six similar U-shaped laminated members 6, 7, 8, 9, 10, 11, arranged in pairs with their ends interfitted so as to form three loops 12, 13, 14, the halves of which are in planes 120 degrees with each other, the completed core consists of three parallel split legs 1, 2, 3, with two Y-shaped yokes 4, 5. Each of the loops 12, 13, 14 is formed from two stacks of trapezoidally-shaped lamination strips of progressively different lengths, the innermost being the shortest. The lamination layers which are stacked to form packets are reversed end-for-end so that their ends are staggered in an interleaved joint. The members 10, 11 are then separated and the member 11 is reversed end-for-end after which the members 10, 11 are put together again with their planes making an angle of 120 degrees with each other. The loops 12, 13 are formed similarly as the loop 14. Fig. 6 shows the completed core made by fitting together the three loops 12, 13, 14. In a modification, the yoke portions of the loops have integral extensions to provide overlapping joints to ensure a better magnetic path between the yoke .members. In a further modification, an additional butt and lap joint is provided at the end of each leg portion and its corresponding yoke portion in order that the Y-shaped yoke can be lifted off as a unit so that coils can be slipped over the legs. Specification 621,675 is referred to.