GB583365A - Improvements in electric switching mechanism suitable for transformer tap-changing - Google Patents

Abstract

583,365. Heavy-current switches; arc-rupturing in switches. BRITISH THOMSON-HOUSTON CO., Ltd. Oct. 18, 1943, No. 17064. Convention date, Oct. 22, 1942. [Class 38 (v)] A transformer tap - changing switch suitable for the circuit described in Specification 500,763, [Group XXXV], and comprising a pair of non-arcing tapselector switches and an arcing- duty switch, is operated by a cam co-operating with a pair of diametricallyopposed followers such that, in a single revolution of the cam, each selector, together with the arcing switch, is opened and then closed. Separate contacts 3, 4 of a ratio-adjuster 5 are connected through halves of a split reactor 7 to common contacts 1, 2 mounted on insulators 8, 9 on the transformer-tank. Selector contacts 10, 11, pivoted to the contacts 1, 2, and engaging fixed contacts 12, 13, connected to conductor 14, are operated by linkwork 20, 21 terminating in followers 18, 19 which engage a cam 16 having a groove with a part offset in the axial direction and rotatable by a shaft 17 interlocked with contacts 3, 4. The arcing contacts 22, 23 are interconnected by a lead 26 and carried on members 28, 29 which are joined by a bar 27 and loosely mounted on the respective cam-follower shafts. By means of normally-separated projections 32 on the members 28, 29 and linkwork 20, 21, the arcing-contacts can be opened by either selector against the action of springs 30, 31, which reclose the arcing-contacts prior to reclosure of the selector. Thus, in one complete revolution of shaft 17, cam 16 opens, say, selector 10 and contacts 22, 23, contact 4 is arclessly moved to the tap where 3 is, and the cam then recloses 22, 23 and 10. Selector 11 and contacts 22, 23 are then operated and contact 3 moved one tap to the left, whereupon 22, 23 and 11 reclose. The reactor 7 averages the voltage of taps 3, 4 and acts as a circulating-current limiter, but load-current effects therein cancel out. The contacts 1, 22 may be shunted by a resistor 33 with the effects described in Specification 17236/43 (as open to inspection under Sect. 91).