GB621674A - Improvements in and relating to electromagnetic induction apparatus - Google Patents

Abstract

621,674. Transformers and inductances. BRITISH THOMSON-HOUSTON CO., Ltd. May 18, 1945, No. 12536. Convention date, May 22, 1944. [Class 38 (ii)] The core of a transformer or inductance is in two parts each formed of a number of flatwise bent strips of magnetic material, the strips meeting at one end of each part with aligned butt joints, and at the other ends with staggered butt joints. The core may be made by assembling strips shown in piles 13, 14 inside a band 15 in the manner and with the apparatus described in Specification 621,675. The strips of the two piles are of different lengths, but have holes 20, 28 spaced equally from the nearer ends of the strips by an amount equal to half the distance between locating pins 17, 18 in band 15. Each core layer comprises a strip from each pile, which strips alternate between the right- and left-hand sides of the assembly as shown in Fig. 2, so that the finished core has aligned butt joints between the pins 17, 18 which pass through the holes 20, 28 to locate the strips, and staggered butt joints on the opposite side. The core may be made rectangular by holding it on the base of a press between three pistons 36, 37, 38 as shown in Fig. 6, forcing a wedge 35 between two suitably shaped blocks placed in the core window, and placing round it a bracket comprising bars 41, 42 spot welded to plate 40, and to a plate 36 at the top shown out of position. After annealing, the two halves of the core are pulled apart, rivets 43 are placed through holes 20, 28 and the core is put round the preformed winding 1, with the aligned butt joints, optionally with insulated spacers 46, in the coil window, and the staggered butt joints are made on the outer side of the coil by pulling out the core ends and letting the laminations drop back one at a time as shown in Fig. 8. Two cores may be placed round the same winding and fastened together by common rivets. The finished cores may be clamped between two frames bolted together, Fig. 1 (not shown). The staggered joints in the outer legs may be built up as described in Specification 621,677, [Group XX].