GB621679A - Improvements in and relating to electromagnetic induction apparatus - Google Patents

Abstract

621,679. Making magnetic cores. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 11, 1945, No. 23394. Convention date, Sept. 11, 1944. [Class 83 (ii)] [Also in Group XXXV] A laminated iron core for transformers and the like is made by bending pre-cut strips of magnetic material to part cylindrical shape and assembling them without the aid of a former into an annular core comprising two separable portions with interengageable ends. A core is made from two groups of strips 9, 10 which are given a permanent hemicylindrical set by passing them through rollers 14, the strips being assembled from inside to outside into a ring. Pins 20, 21 are passed through holes 11, 12 offset from the centre of the strips which are reversed in alternate layers, so that the laminations or groups of two or three laminations of each core half engage in staggered butt joints. Bands 23 are placed round the core which is given a rectangular shape by driving wedge 25 between tapered blocks 22 inserted in the core window. Pistons 26, 27, 28 pressing on the sides of the core may be used to assist in shaping the core without opening the joints, Fig. 7, and when the shape is satisfactory, plate 30 is welded to straps 31, 32 fixed to plate 29. The core is then annealed, disassembled and reassembled round the winding 5 (Fig. 9), rivet 32 being placed in holes 10, 11. The reassembly may be done a few sheets at a time if necessary. A core with staggered and butt joints in the yokes may be made from groups of laminations of equal length, and in assembly a magnetic holding device may be used, Figs. 12, 14 (not shown). The cores may be annealed whilst on their sides under pressure exerted by weights, Fig. 15 (not shown). In assembling cores which have joints in the yokes, around the coil, some laminations may have to be slightly bent, Fig. 16 (not shown). To avoid this the joint may be at opposite corners or the yoke only may be removable, Figs. 17, 18 (not shown). The winding 86 may be wound round two half cores 84, 85, Fig. 20. Specifications 7856/89, [Class 38], 621,675 and 621,677 are referred to.