GB731215A - Improvements in and relating to magnetic cores for stationary electrical induction apparatus - Google Patents

Abstract

731,215. Transformers. GENERAL ELECTRIC CO. May 26, 1953 [May 27, 1952], No. 14628/53. Class 38 (2). A three-phase three. legged core structure has the leg and yoke laminations split so as to form an outer core section separated by an air gap from an inner core section connection being made between the sections at the centre leg portion, all the joints between laminations being butt joints and adjacent lamina layers being shifted to produce overlapping joints with respect to the layers. A laminated core 1 comprises an outer core section 2 and an inner core section 3. The outer core section is formed of leg laminations 4, 6 and yoke laminations 12 ... 15 whilst the inner core section is formed of leg laminations 5, 7 and yoke laminations 16 ... 19. Thus, each leg and each yoke lamination of the core 1 is formed in two parts spaced apart from each other, such as 4, 5. Each laminaation of the centre leg is also formed in two parts 8, 9 which extend between the inner edges of the yoke laminations 16, 17 and 18, 19, the outer and inner core sections being connected by insert pieces 10, 11. The core 1 is built up in a three-step pattern repeated a plurality of times and in order to avoid the joint lines being coincident the successive lamination layers are shifted' so that the joints in successive layers are overlapped; whilst to remove coincidence in the joint lines of the insert pieces, the pieces 23... 25 (see Fig. 2) in one pattern are made successively wider. Each pattern may comprise any num. ber of steps and each layer may comprise a number of laminations. In a further embodi. ment the outer yoke members may extend the complete width of the core, the insert pieces then butting the inner edges of these members. In such an embodiment one or more of the insert pieces may be dispensed with the two parts of the centre leg laminations then extending between the yoke members. If more than one insert piece is dispensed with the centre leg laminations may be notched to receive the yoke members of the inner core section, which notches may be successively deeper in each pattern to provide overlap of the butt joints. Specifications 644,097 and 657,856 are referred to.