GB1012911A - Improvements in voltage regulating transformers - Google Patents

Abstract

1,012,911. Transformers. FOSTER TRANSFORMERS Ltd., and T. COURTNEY. Sept. 4, 1963 [Sept. 4, 1962], No. 33819/62. Heading H1T. In a tap-changing system smooth voltage transition is obtained between adjacent tapping studs 6 of the main transformer winding 5 by inclusion in the connections to the load circuit of auxiliary windings 12 and 13 the voltage of which is bucked or boosted by voltages obtained from contacts 11 moving over at least one winding 10 of a toroidally wound auto-transformer fed by another auxiliary winding 8 on the main transformer. The brushes 11 are mechanically linked to the main tapping contacts 7 and when the latter are on the same tapping stud (e.g. the end stud), the brushes 11 are in contact with opposite ends of the winding 11 and each carry half the load current. From this position one brush 11 moves over an insulated track (shown as a dashed line semi-circle) disconnecting from the load circuit its associated main tapping contact 7 which can them make off-load connection with the next contact stud 6. The other brush 11 picks up from winding 10 a voltage which diminishes to zero as the brush 11 reaches the centre of winding 10 and then increases in the opposed direction, this voltage opposing or adding to the voltage of the winding 12 or 13 connected to that brush in dependence on the position of the latter. The brushes may engage additional short end portions of a higher resistivity wire when engaging or leaving the winding (Fig. 4, not shown). There may be two auto-transformer windings 10 fed in parallel by the centre-tapped winding 8 on the main transformer 5 (Fig. 2, not shown) and having moving contacts 11 connected in parallel with one another and in series with the windings 12 or 13 on the main transformer. In another arrangement the windings of two fine switch transformers 91, 92 (Fig. 3, not shown) are in series but have their output circuits in parallel.