GB455176A - Improvements in and relating to dynamo electric machines - Google Patents

Abstract

455,176. Rotary converters; inductor alternators. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Nov. 18, 1935, No. 31903. Convention date, Nov. 17, 1934. [Class 35] In a machine for converting alternating to direct current and vice-versa of the type comprising a toothed rotor and a toothed stator having teeth of the same pitch as the rotor but disposed in groups spaced from each other by odd numbers of half tooth pitches so that the total flux is nearly constant, the stator poles are arranged in sets each comprising two similar groups arranged on each side of a middle group and equidistant therefrom so that the flux distribution remains nearly symmetrical about the central line of the middle group. The Figure shows a machine comprising two sets of poles each containing a central group 25, 28 and two side groups 26, 27 and 29, 30 spaced as described and carrying generating windings 32, 35, 31, 33 and 34, 36 respectively. The windings 32, 35 and 36 are wound oppositely to the windings 31, 33, 35, the whole being connected in series. The two groups of poles are enclosed in directcurrent exciting windings 16, 17 respectively. The rotor is provided with slots 21 containing a direct-current winding, connected to a commutator 22 on which bear brushes 23 on the central line of the pole-groups 25, 28 of the stator. Generating windings 43 may be placed on the stator ring between the polegroups instead of on the poles themselves. To prevent locking of the rotor on starting through armature reaction compensating windings producing a transverse field may be placed on the stator poles, or the stator ring, or in the stator pole slots. A method is explained by which the machine is operated at such saturation that the alternating-current voltage remains approximately constant when the speed of rotation decreases on a drop in direct current voltage. The invention is also stated to be applicable to simple alternators.