GB263833A - Improvements in and relating to coil windings for dynamo-electric machines - Google Patents

Abstract

263,833. British Thomson-Houston Co., Ltd., (Assignees of Summers, I. H.). Dec. 29, 1925, [Convention date]. Coils.-In a method of reducing the eddy current losses in multiple layer coils for dynamoelectric machines by transposition of the component layers of a laminated coil conductor from slot to slot, a twist of 180‹ is given to the laminated conductor at one end of the coil. The Specification analyses the parasitic voltage distribution across the conductors in a given slot into an elementary parabolic component and a linear component which increases from zero at the bottom of the slot to a maximum at the top of the slot in direct proportion to the number of conductors in the depth of the slot, and it is shown that the present method of twisting approximately balances out the effects of the linear components in the two sides of the coil. Fig. 1 shows a two-turn, two-layer coil composed of four-strand conductor, each strand being made of two wires and insulated from the other strands. The coil has the usual reversing ends 2 and, according to the invention, it is given a twist of 180‹ in such turn, as shown at 6, the resulting effect being shown in Fig. 2, which is a section on the plane 2-2, Fig. 1, and in which a selected strand is shown in shaded lines. Fig. 3 shows a three-turn three-layer coil having four double strands insulated from each other as in Fig. 1. The coil has the usual reversing ends 12 and has a single twist 16 through 180‹ at the front end. It is shown in the Specification that the linear parasitic voltage components completely cancel out in the form shown in Figs. 1 and 2 and that in the form shown in Fig. 3 they are reduced to one-ninth of the value which they would have without the twist at 16. Fig. 3 shows the twist in the top conductor at the connection end of the coil, but it may also be at the other end of the coil in the end of the bottom conductor in the top coil side, an arrangement which gives a smaller reduction of losses but a coil twist at a place where there is more room available than there is at the connection end. The terminals 4, 14 may also alternatively enter the slots at the top in place of the bottom as shown, in which case the point of twist is placed at the back end of the coil one turn distant from the terminal.