GB622538A - Improvements in and relating to electric induction apparatus - Google Patents

Abstract

622,538. Making transformer &c. cores. BRITISH THOMSON-HOUSTON CO., Ltd. March 21, 1947, No. 7847. Convention date, March 21, 1946. [Class 83 (ii)] [Also in Group XXXV] A method of making a laminated magnetic core for electromagnetic induction apparatus comprises cutting from a long strip a number of pieces having differing lengths, stacking the pieces against each other in order of their lengths and applying means to retain the pieces in assembled relationship, bending the stacked pieces to form a closed loop having one joint in which loop each piece forms a complete single layer, shaping the loop into a core having a straight winding leg and finally annealing the core to relieve the strains therein. The pieces 14, Fig. 5, have the most favourable magnetic direction parallel to their longitudinal axis, two holes 15, 16 being punched in each strip to accommodate the pins which serve to retain the pieces stacked alternately reversed endwise, Fig. 6. A number of sections such as 6, 7, 8, Fig. 1, of differing widths may be used to form a cruciform core, Fig. 2, to improve the space factor of the window of the associated winding 21, Fig. 11, the sections being held together by straps 10, Figs. 1, 2. The core sections are capable of hinging, so as to open the joints 9, Fig. 11, which are preferably at one end of the central winding leg, in order to assemble the winding 21 thereon. Various alternative embodiments are described showing differing positions of the punched holes in the pieces, differing methods of holding the stacked pieces together to form a cruciform core and differing types of joints, including overlapped butt joints more than one piece thick, scarfe joints and joints having a greater cross-section than elsewhere in the core to reduce the losses therein.