GB287167A - Improvements in or relating to alternating-current electrical generators - Google Patents

Abstract

287,167. Lorenz Akt.-Ges., C. March 18, 1927, [Convention date]. Inductor-alternators; rotary converters.-In an alternating-current inductor generator operating on the homopolar principle, the pitch of the generating winding is equal to a fraction of half the pitch of the inductor teeth, and the coils of the winding are so connected in series that a frequency higher than that corresponding to the inductor tooth pitch is generated. The method of operation is explained with reference to Fig. 1 wherein the direction of the flux is represented by the dotted arrows, and the coils are assumed to be wound in consecutive pairs of stator slots n1.- n2, n3-n4, &c., and therefore the coil pitch equals one half of the tooth pitch of the inductor. To obtain currents of higher frequency, the stator slot pitch is decreased, i.e. for triple frequency a stator slot pitch of one third of half the rotor tooth pitch is adopted as shown in Fig. 2. Fig. 3 shows the invention applied to a machine generating currents of three different frequencies for telephone signalling purposes. The armature winding Wa of a continuous-current motor is connected to slip-rings s from which current having a frequency for example of 25 may be obtained. The pole shoes of the poles N, S are provided with a winding W150 giving a frequency of 150, and a second winding W450 giving a frequency of 450. The pitch of the winding W150 is equal to half the armature tooth pitch as in Fig. 1, and the pitch of winding W450 is equal to one third of half the armature tooth pitch. A greater, number of currents of different frequencies may be generated in a single machine. One or both slip rings may be dispensed with and the spindle or one of the commutator brushes may be used for taking off the low frequency current. One of the higher frequency windings may be located on one pole face and the other winding on the other pole-face and the winding arrangement N1-N2, N2-N3, N3-N4 &c. may be adopted, successive coils being oppositely wound.