GB1110314A - Improvements in and relating to on-load tap changing gear - Google Patents

Abstract

1,110,314. Mechanical switches. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 20 July, 1965 [31 Aug., 1964], No. 35538/64. Heading H1N. A tap - changing arrangement comprises selector and diverter switches and a means for operating the switches accommodated in a common enclosure filled with an insulant. There are two selector switches (S1, S2) two diverter switches (D1, D2) and two diverter resistances R1, R2 (circuit diagram, Fig. 1, not shown). Selector switch S1 comprises fixed contacts 1, 3 . . . 15, 17 mounted on an insulating web 18 on a plate 19 over an opening in the cover 20 of a transformer tank, with conductors 21 from the fixed contacts, and a contact finger F on a Geneva wheel 23 operated from spindle 24. Selector switch (S2) comprises fixed contacts 2, 4. . . 14 16 mounted on the rear of web 18. Each diverter switch (D1 D2) comprises two vacuum switches (M1, A1, M2, A2) (Fig. 1) of which switches A1, A2 are shown, switches (M1 M2) being mounted behind them, on a board 25 mounted on pillars 26 from a bracket 28 on a web 18. Switches A1 A2 are biased closed by springs 31 and opened by cam 38 on operating spindle 24 bearing on rollers 36, 37 on bell-crank levers 32, 33. Resistors R1, R2 are mounted as shown. In an alternative embodiment, Fig. 3 (not shown), to enable access to the vacuum switches without draining the enclosure of oil, a removable cover-plate is provided at the top of the tank and the vacuum switches are mounted on a bridge structure (44) which can be raised above the oil level (OL) by rotating lifting screws (47). Also there are two operating spindles, one for selectors S1 (S2), one for cam 38 operating the diverter switches. A wiring diagram is given in Fig. 4 (not shown), and Fig. 5 (not shown) gives the diverter switching sequences for a change of tapping position. Alternative circuits to allow for fine and coarse control are given in Figs. 6 and 7 (not shown), and an alternative selector switch embodiment to provide this is given in Figs. 8, 9 (not shown) similar to that described above except there is no web 18, base 19 being skirted, with the appropriate conductors projecting through carrying on their ends fixed contacts, the Geneva wheel being operated through gearing from the operating spindle, and an additional coarse control finger (CC) is mounted on a boss on base 19 selecting between two coarse control fixed contacts. In a further embodiment, Figs. 10, 11, 12 (not shown), the arrangement described above with respect to Fig. 2 is provided with mechanical diverter switches instead of vacuum switches, comprising a pivoted switch arm (55) operated from a roller in a groove in cam (58) on the operating spindle, switch arm (55) carrying bifurcated spring- loaded contacts (53, 54) changing over between fixed contacts (X, XA, Y, YA). The contacts may be as described in Specification 1,071,417.