GB517121A - Improvements in and relating to means for compensating voltage variations in supply circuits - Google Patents

Abstract

517,121. Transformer arrangements for electricity supply. BRITISH THOMSONHOUSTON CO., Ltd. July 18, 1938, No. 21269. Convention date, July 17, 1937. [Class 38 (iv)] In order to avoid flickering of incandescent lamps where the load includes motors, arc welders and other heavy loads on the supply, the lighting and power loads are drawn from the two sides of a three-wire circuit supplied by the secondary of the power transformer and the neutral common to the two loads includes an impedance' equal in value to the equivalent primary circuit impedance with respect to the secondary current taken by a least one of the loads. By these means, the power components of the two load currents flow in opposite instantaneous directions in the common neutral conductor and the lighting circuit is unaffected by heavy variations in the other load circuit. The mathematical considerations underlying the invention are set out in the Specification as shown in Fig. 1, the secondary 12 has the neutral 13 connected to its mid-point with the imped- .ance Z3 in its circuit, and.the lamp load 14 is, connected between the neutral and one outer and two induction motors 16 between the neutral and the other outer. As applied to a three-phase transformer, in one form shown in Fig. 3, the three-phase induction motor load 16 is connected across, the delta-connected secondary N2 which has its phase windings extended by windings N1 to afford a supply for the lamp load, inductances Z3 of the required value being connected in the common neutrals.