GB662499A - Improvements relating to on-load tap-changing circuits particularly for transformers - Google Patents

Abstract

662,499. Transformers. BRITISH THOMSON-HOUSTON CO., Ltd. (General Electric Co.). July 14, 1949, No. 18605/49. Class 38 (ii). In a tap changing system for a transformer the major part of the arcing duty is performed by a switch connected across the secondary of an insulating transformer the primary of which is included in the tap changing circuit, thereby permitting servicing of the arcing duty switch whilst the transformer is on load. The tapped transformer winding 1 is connected to terminal 11 by way of tapping switches 6, 7, the split reactor 13 and transfer switches 14, 15, whilst across the leads between the reactor 13 and transfer switches 14, 15 is connected (a) switch 16, and (b) the insulating transformer 19 through switch 18, the secondary of the transformer being short-circuited by the arcing duty switch 17 and preferably earthed. Cams 28, 30, 34 actuating switches 16, 18 and 17 are rotated at twice the speed of cams 32, 33 actuating switches 14, 15 and the Geneva mechanism 23 actuating the tapping switches 46, 47. The system is shown in its half-cycle or bridging position and upon rotation of the cams by motor 21 or by hand, switches 14, 16, 17, 18 open in this order and then tapping switch 6 is moved to tapping 3 at the quarter cycle and the switches then closed in the reverse order to the full cycle position. The system is provided with an interlock to ensure that the system cannot be stopped in its quarter cycle position, i.e. one transfer switch open. The transformer 19 may be step-up or step-down to suit the arcing duty of switch 17.