GB191514377A - Dynamo Electric Machines. - Google Patents

Abstract

14,377. Neuland, A. H. Oct. 11. Commutation, improving by means of resistances; inductor-alternators; pole-pieces; rotary machines; windings.-Relates to commutator dynamo-electric machines of the type described in Specification 14,160/15, and consists in providing the armature with a multiple winding and connecting it to commutator segments so that the ratio of the angular span of the commutator over which a series of brushes collects current to the angular span of the commutator for a pair of pole windings is considerably greater than the ratio of short-circuited conductors to total armature conductors. The machine may be constructed with a homopolar rotor and stator as described in Specifications 13,287/15 and 101,447; or it may have wound salient poles as shown in Fig. 2. The stator and rotor are formed with different numbers of teeth, so that a rotating magnetic field is produced having a higher angular velocity than that of the rotor. In the construction shown in Fig. 2, the rotating magnetic field corresponds to an eight-pole field. The teeth on the N-poles are separated from those on the S-poles by half a tooth-pitch. An eightpole multiple armature winding comprising eight separate windings is shown in Fig. 3, each winding being composed of 32 coils connected to 32 commutator segments. The eight conductors in each slot are connected fan-wise to commutator segments separated from each other by eight segments. Direct current is collected from the commutator by 28 positive and 28 negative brushes, the point of contact of the brushes with the commutator segments connected to each winding progressing with the same angular velocity as that of the rotating magnetic field. By altering the number of brushes so that the point of contact rotates at a different angular velocity, alternating-currents are produced. Although at any instant all the brushes are collecting current, two coils only in each pole-winding are short circuited. The currents in the short-circuited coils may be diminished by inserting resistances between the brushes and the collecting-rings. The magnetic field may be strengthened by means of an eight-pole induced winding on the stator connected across condensers, the winding preferably being polyphase.