GB424408A - Improvements in and relating to transformer tap changing arrangements - Google Patents

Abstract

424,408. Transformers. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Nov. 9, 1934, No. 32323. Convention date, Nov. 9, 1933. Addition to 400,962. [Class 38 (ii)] In an arrangement for tap-changing under load in which an intermediate tap is permanently connected to the load circuit through a device offering low impedance only when subjected to the full voltage of the transformer winding as when the tap-changing switch is being actuated as described in the parent Specification, the device comprises a pair of oppositely connected grid-controlled gaseous discharge devices 7, 8 the grid circuits of which are controlled either by the main contacts of the tap-changing switch 3 or auxiliary contacts thereon so that the discharge devices are blocked during normal operation and rendered conductive during actuation of the tap-changing switch. The Figure shows the control circuit of one grid only which circuit includes a change-over switch 13 actuated by a cam 16 on the spindle of the tap-changing gear whereby the required grid control is effected. Heating of the cathodes of the devices 7, 8 may be discontinued during normal operation of the transformer, the heating circuit being completed only at the commencement of the tapchanging operation, starting of the tap-changing motor 5 being delayed to allow the cathodes to reach operating temperature.