Patent GB-135533-A (GB)
IPC: H02K3/14
Abstract: 135,533. British Thomson - Houston Co., Taylor, H. W., Clough, F. H., and Whitaker, F. P. Aug. 23, 1918. Coils and conductors; windings. - Relates to arrangements for preventing local currents from circulating in the armature windings of alternating-current machines having deep slots in which the conductors are divided into a number of separately insulated bars or laminations. These local currents are produced by the magnetic' flux passing from one side of the slot to the other across the conductors by reason of the load current in the conductors; the flux passing across any conductor in a slot may be regarded as partly variable (i.e. differing from lamina to lamina in the conductor) depending on the current in that same conductor, and partly constant depending on the total current in the conductors below the conductor in question; the second conductor from the bottom of the slot will thus be subjected to one constant element of flux, the third conductor to two constant elements, and so on. According to the invention, the separate laminµ of which a conductor consists are so connected to one another at the ends of the half-turns that in one half of the conductors the order of the laminae is reversed with respect to the order in the other half, and that the total number of constant elements of flux linking the conductors in the half-turns in which the lamimµ appear in the unreversed order is equal, as far as possible, to the total number of constant elements of flux linking the conductors with the reversed order of lamination. Figs. 2 and 6 show respectively reversed and unreversed forms of end connexions. Fig. 8 shows two slots situated substantially a pole-pitch apart and containing the conductors of a two-turn coil of a twolayer winding, each conductor comprising five lmninµ 1 - - 5, and it will be seen that the order of lamination of conductors 1, 4, which are connected together is the reverse of the order of lamination of conductors 2, 3 which are also connected together. Instead of making the connexions within the coil itself, the separate laminµ may be continued from half-turn to halfturn and also from coil to coil; but, at even fractional positions throughout the winding, the order of the laminµ in a conductor is reversed. Figs. 9 and 11 illustrate the application of the invention in the case of a two-phase two-layer winding with coils of a fractional pitch of two-thirds the pole-pitch, each conductor being split up into three insulated bars 1, 2, 3; the winding of one phase only is shown. The bars in the upper half of slot 1 of the first pole are connected to the bars in the lower half of slot 5, then to the bars in the upper half of slot 2, and so on. In passing on to the second pole, the order of the bars is reversed, the bottom conductor of slot 11 being joined to the top conductor of slot 7, then to the bottom conductor of slot 12, and to the top conductor of slot 8, and so on. In slots 1, 2, 3 of the first pole, the bar 1 is transferred gradually towards the bottom of the slot, whereas, in slots 7, 8, 9, it is transferred towards the mouth of the slot. In a modification, Fig. 10, the conductor is divided into six bars corresponding to the total number of coils per phase, 'and these bars are divided into two groups of three each. In form-- ing the coils, the bars are transferred each within its individual group and not with reference to the conductor as a whole. Specification 10919/13 is referred to.