GB181070A - Improvements relating to the rectification of alternating currents of electricity - Google Patents

Abstract

181,070. Pollock, S. A. Feb. 25, 1921. Commutator switching-arrangements.-In a rectifying- system, particularly adapted for load circuits containing storage batteries or other sources of back electromotive force, each positive and negative half - wave of current passes in series through the polarized armatures d, c of two relays D, E, the electromagnets of which are energised by currents having a phase difference for the purpose of interrupting the load circuit during the period of each half - wave when the applied voltage is equal to or less then the back electromotive force of the load. In the arrangement shown in Fig. 1, the windings D<1>, E' o! the electromagnets are energized in shunt circuits connected to the alternating-current source A, and the phase differences are produced by capacities F, G, of such a value that the angle of lag between the current and the applied electromotive force in one circuit is equal to the angle of lead in the other circuit. The alternating-current source A is connected to the primary winding a of a transformer with two secondary windings b, c. which are a.lternately connected to the battery or other load O through contacts b<1>, b<2> or c<1>, c<2> on the relays. The connections to the load circuits are only completed when both armatures d, c occupy similar positions, which, owing to the phase differences in the currents energizing the windings D<1>, D<2>, only occurs during a part of each half-wave of the alternating-current. In a modification, Fig. 2, the phase differences in the electromagnetic fiuxes are varied in accordance with the actual back electromotive force existing at any moment. For this purpose a third relay R is provided, with a winding R<1> connected in shunt with the alternating-current circuit through a resistance or reactance s. A polarized armature t of this relay connects the battery O alternately to windings D<2>, E<2> and D<3>, E<3> on the relays D, E. These windings are arranged to increase the angles of lag and lead in the electromagnets of the relays D, E by equal amounts, the actual value of the increases depending on the back electromotive force of the battery. In this arrangement, the capacities F. G in the circuits of the main windings D<1>, E<1> of the relays D, E are of such values that the currents in these windings are in phase with each other. The currents in the windings energized from the relay R are in Quadrature with the currents in the windings D'. E', the windings E<2>, E<3> being connected in reverse direction to the windings D<2> D<3>. Specification 119,081 is referred to.