GB929549A - Improvements relating to regulating transformers - Google Patents

Abstract

929,549. Control of D.C. motors. ENGLISH ELECTRIC CO. Ltd. Nov. 16, 1959 [Nov. 14, 1958], No. 36701/58. Class 38 (3). [Also in Group XXXV] For regulating the supply to D.C. traction motors M1, M2 (Fig. 3), the supply transformer is provided on the lower part of its core 10 with a short-circuited winding 10d and, in addition to one or more fixed secondary windings 10b, 10c inside the primary winding 10a, there is provided a movable secondary 10e which can be connected by switches W1- W4 to buck or boost to a variable degree, the voltage supplied by windings 10b, 10c. Winding 10e in its maximum voltage position may develop a voltage which is less than, equal to or more than the sum of the equal voltages produced by 10b or 10c and may be centretapped, its ends and centre being connected through sliding brushes to bus-bars 14, 15 and 13. The minimum voltage (or a reverse voltage) is obtained with 10e in its upper position and switches W1 and W2 closed so that its voltage is opposed to the voltages of 10b and 10c while a maximum voltage equal to the sum of the voltages of 10b, 10c together with the maximum voltage of 10e is obtained with 10e in its uppermost position and W3 and W4 closed. One of the fixed secondary windings and the centre tap may be omitted. A further set of fixed secondary windings with a further set of four contactors may be added. This further set is then bucked or boosted by the first set of windings, the movable winding being arranged to move down and up twice for the full range of voltage variation.