GB209183A - Improvements in or relating to dynamo-electric machines - Google Patents

Abstract

209,183. Festarini, G. M., and Metro politan-Vickers Electrical Co., Ltd. Oct. 4, 1922. Rotary converters and transformers. -A machine for converting electrical energy of one form to another form comprises one or more armatures, with windings connected to commutators or slip rings, driven by an auxiliary motor in an unwound iron ring which completes the magnetic circuit of the armature currents. In Fig. 1, two independently-driven armatures 1 in unwound field members 5 are employed for converting continuouscurrent from one constant voltage to another, the ratio of the voltages being variable. Each machine has pairs of brushes 8, 9, 8<a>, 9<a> ninety electrical degrees apart. Current from the constant voltage mains 7 produces constant voltage at the brushes 9<a>, the ratio of the voltages depending on the speeds of the armatures. Fig. 2 shows means for converting single-phase power from mains 7 to three-phase power of the same frequency. The armature has three windings connected respectively to slip-rings 14 and 15 and a commutator 3 on which are pairs of short-circuited brushes 8, 9 ninety electrical degrees apart. When the armature is driven at or about synchronous speed, three-phase, current is supplied at synchronous frequency to the mains 10. Inductances 16 may be employed to check alternating-currents between the bushes 8, 9. Single-phase power at one frequency may be transformed to polyphase power at variable frequency by a machine, Fig. 3, having three windings connected respectively to slip-rings 14, supplied from the single-phase source 7, a commutator 3 having pairs of shortcircuited brushes 8, 9, and another commutator 4 having as many brushes 17 as there are phases in the supplied netword 10. The armature is driven at or near the synchronous speed of the supply 7 and the brushes 17 may be stationary, in which case they give twice the supply frequency, or they may be driven at a speed which corresponds to the required frequency at 10. An alternative machine for giving the same transformation has single-phase supply brushes bearing on one commutator, pairs of short-circuited brushes on another commutator, and polyphase brushes on slip-rings, the short-circuited brushes being rotated at or near the single-phase synchronous speed and the armature as a whole at a speed which determines the polyphase frequency. In the form shown in Fig. 5, single-phase current fed to a slip-ring winding at 14 is converted to continuous-circuit on a commutator 9 by means of a third winding connected to a commutator 3 having short-circuited brushes 8, 8<a>. The armature is driven at synchonous speed and the brushes 8, 8<a> at or about twice synchronous speed. In all of the machines, excepting those shown in Fig. 1, two or more of the armature windings may be combined into a single winding with slip-rings and commutators as described. The field ring may have commutating poles and windings, in which case it is rotated with the brushes.