GB445490A - Improvements in or relating to dynamo-electric machines - Google Patents

Abstract

445,490. Cores and coils for dynamoelectric machines. WESTINGHOUSE ELECTRIC MANUFACTURING CO., East Pittsburg, U.S.A.-(Assignees of Jones, M. F. ; 534, Greendale Avenue, Edgewood, Pennsylvania, U.S.A.) Nov. 9, 1934, No. 32317. Convention date, Nov. 11, 1933. [Class 35] The core of a dynamo-electric machine has winding slots formed with a rectangular bottom portion A, an upper intermediate portion B having the same cross-sectional area but a smaller depth, these two portions each housing the same number of conductors, and a top portion comprising a lower wide part 22 and a neck 21 in line with the lower part having a transverse dimension substantially equal to the transverse dimension of the bottom slot portion. The invention is particularly applicable to railway motors and the object is to improve commutation It is explained in the Specification that the most diffcult conductor to commutate satisfactorily is the lowest one in the slot by reason of its self inductance. It is explained further that if during commutation of one conductor, another conductor in the same slot forms part of a coil which is still short circuited by a commutator brush, damping currents will be set up in this coil and the voltage induced in the conductor in question is reduced. Accordingly it is arranged that the la,st conductor in a slot to be commuted will be as near the top as possible. As shown in Fig. 5, the conductors are rectangular in cross-section and are positioned with their longer dimension b vertical in the lower slot portion and with their shorter dimension a vertical in the upper portion. The upper conductors are introduced edgewise through the neck 21 and rotated through 90‹ in the widened part 22 before placing in position and the slot is closed by an insulating wedge 23. The conductor section is changed, both at the commutator end and at the back end of the armature while keeping the cross-sectional area constant either by forming separate pieces and welding them to the conductors or by drop forging or hot pressing the ends of the conductors. Alternatively, the conductors may be assembled as a unit, the ends flattened, twisted through 90‹ and finally pressed to the required shape, for example as shown in Fig. 47. A conductor in the upper part of a slot is connected to a conductor in the lower part of another slot and the arrangement may be such that for one direction of rotation, the last conductor to commutate will be the lowest in the top group, and for the other direction, the uppermost in the bottom group.