GB217607A - Improvements in and relating to electric transformers - Google Patents

Abstract

217,607. British Thomson-Houston Co., Ltd., (Assignees of Blume, L. F.). June 16, 1923, [Convention date]. Regulating transformers.-The voltage of a transformer is adjusted without interrupting its operation by dividing one of the winding into four sections, each of which is provided with a number of tappings, and connecting two of the sections of a number of parallel winding sections to the line, while the remaining sections are connected in parallel between the line sections. In the arrangement shown, for supplying lowvoltage current to an induction furnace from a high-voltage source, the secondary winding is divided into four sections 1 - - 4 which are distributed between sections of the primary winding and connected in parallel to the load circuit 5. The high-voltage primary winding comprises sections 6, 7, connected to the lines 10, 11, and intermediate sections 8, 9 in parallel, all four sections being symmetrically arranged to avoid high reactance. Each of the sections 6, 7 comprises two parallel groups of turns with tappings connected to switches 12, 13, and the remaining sections comprise single groups of turns with tappings connected to switches 14, 15, the latter being connected through circuit-breakers 16, 18 and reactances 17, 19 to the inner ends of the sections 6, 7. A simplified diagram of connections with the switch levers in the extreme positions, giving minimum voltage in the secondary winding, is shown in Fig. 2. When it is desired to adjust one of the switch levers, the corresponding circuit-breaker 16 or 18 is opened. The adjustments are so effected that the electrical balance between the different winding sections is disturbed as little as possible in order to avoid local circulating-currents in the sections 8, 9; such circulating currents as occur are limited by the reactances 17, 19, which are in series to the circulating currents but in parallel to the primary current. Additional pairs of tapped intermediate winding sections may be provided in order to increase the range of adjustment.