GB644097A - Improvements in and relating to magnetic cores - Google Patents

Abstract

644,097. Transformers. BRITISH THOM. SON-HOUSTON CO., Ltd. Jan. 9, 1948, No. 773. Convention date, Jan. 9, 1947. [Class 38 (ii)] A magnetic core for an induction apparatus comprises superposed flat lamination layers each of which has two yoke portions and at least two leg portions, each of the yoke portions in a layer comprises at least one piece of a lamination strip and each of the leg portion in a layer comprises at least two pieces of lamination strips of different width produced by splitting longitudinally the leg portions. The pieces in one of every alternate pair of contiguous leg portions are of different lengths and make butt contact with the same yoke piece in the same layer. Fig. 1 shows a 3-phase core having three longitudinally split legs 5, 6, 7 and two yokes 8, 9. The top layer 1 is lifted off the stack to reveal a second layer 2. All the odd-numbered layers are exactly the same and all the even ones are similar to one another but differently formed from the odd layers. The width of each leg portion is equal to that of each yoke portion. The lengths and widths of the pieces of the split leg lamination strips are such that when the yoke laminations make butt contact with their respective leg laminations in the same layer none of these butt joints in adjacent layers-will coincide with each other when the layers are superposed to form the stack. Fig. 2 shows a modification in which the yoke laminations are also split longitudinally. All the layers are identical, but every alternate layer is rotated 180 degrees about an axis perpendicular to the lamination plane before it is superposed on its adjacent layer. In a further modification, a single phase core has two split yokes. In another modification, a single phase core has both its legs and yokes longitudinally split. In further modifications, single phase and 3-phase cores have all the legs and yokes longitudinally split in three strips in each layer. In all the modified forms, the joints in adjacent layers are staggered with respect to each other.