GB575564A - Improvements in or relating to three-phase core structures for electrical induction apparatus - Google Patents

Abstract

575,564. Transformer cores. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. March 27, 1944, No. 5624. Convention date, March 27, 1943. [Class 38 (ii)] A three-phase magnetic core comprises three V-shaped members formed of layers of magnetic material bonded together by insulating material and bent across the width of the strips, the two ends of each member being so shaped that they form butt joints with the ends of the other members at the axis of the core from which the three members radiate in directions mutually displaced by 120 degrees. A strip of magnetic material may be continuously wound to form the rectangular loop shown in Fig. 3, the laminations being separated and bonded by a plastic insulating material. Cuts 24, 25 inclined at an angle of 120 degrees at the top and bottom of the coil make two V-shaped cores with surfaces at the ends so shaped that three cores 4, 5, 6 may be placed together as shown in Fig. 1 to form a three-phase structure, round the three legs 7 of which windings 1,'2 and 3 may be placed. The surfaces forming the butt joints between core members extending between the axis 12 and outer edges 10, 13, 14 may be machined and then etched to remove burrs as described in Specification 540,662. The core members 4, 5, 6 are held together by straps 16, 17, 18 which hook into a triangular member at the bottom and are held by adjustable screw connections 19, 21 in a triangular member 15 at the upper end. Also described is a construction in which each core member is divided centrally by a conducting strip to prevent cross flux, insulated from the laminations and lying in a plane containing axis 12, Figs. 5, 6 (not shown). As a further modification, core members of cruciform section are described which are made similarly to those previously described but from a strip which is wider at its middle portion, Figs. 7-10 (not shown). Preformed coils may be placed on the cores which are first cut across the legs 7 and then joined by a butt joint, or the low voltage winding may be wound on the core and the high voltage winding slipped over it.