GB197410A - Improvements relating to alternating-current dynamo-electric machines - Google Patents

Abstract

197,410. Miller, L., Field, A. B., and Metropolitan-Vickers Electrical Co., Ltd. Feb. 13. 1922. Windings.- The windings of each phase in alternating-current machines for ship propulsion or other purposes are divided into section, the conductors of one section being in different slots from those of another section of the same phase, each slot containing the sides of two coils and the conductors of each section being similarly located with reference to the magnetic field so that the terminal voltages generated in all sections of a given phase winding always have substantially a common value. A fault on one section is therebv limited to that section and the machine may continue running on the other section of the phase. Fig. 2 shows one phase winding of a four-pole machine having six slots per pole. The winding consists of two sections T1' Y1, shown in heavy lines, and T2, Y2, shown in light lines, the full and dotted lines respectively representing the top and bottom conductors in the slots 1 - - 24. The two sections are normally paralleled by joining T1, T2 and Y1, Y2 and the winding entails two forms of coil. Fig. 3 shows the three complete phase windings of a four-pole machine having six slots per pole and all coils chorded to a four-slot pitch. The windings are shown displaced vertically and each phase comprises two sections shown by heavy and light lines. Thus, phase A consists of two sections T<1A> Y<1A>, T<2A> Y<2A> paralleled at the terminals T<A>, Y<A>. Each slot contains the sides of two coils which are not in the same section of a phase winding and the coils of a section of any one phase are always in a slot with those of a corresponding section of another phase. Thus, a fault on a coil, say, in the thick-lined section of phase A in slot 9 can only affect the thick-lined coil of phase B in the same slot. The method of winding may also be applied to concentrically wound coils, and in place of being in parallel, the sections may be connected in series as shown in Fig. 5 which shows a connected generator G and motor M, each having two sections in series per phase. If a fault develop in the motor at E, the corresponding outer sections in all phases may be cut out and the machines may run at reduced power, as shown in Fig. 6. Alternatively, only the faulty outer section E and the corresponding generator section may be cut out, the ends of the inner sections of the affected phase windings and the star-points of the two machines being ccnnected, thus enabling the machines to run with a symmetric loading.