GB649096A - Improvements in and relating to transformer tap changing under load systems - Google Patents

Abstract

649,096. Transformers. BRITISH THOMSON-HOUSTON CO., Ltd. June 5, 1947, No. 14893. Convention date, June 7, 1946. [Class 38 (ii)] [Also in Group XXXVII] An on-load transformer tap-changing system comprises ratio adjusters co-operating with taps of the windings, a reversing switch and a set of transfer switches wherein the transfer switches are actuated from a train of cascaded Geneva gears, the first gear in the train being actuated by a lay-shaft driven from the main drive shaft driving the ratio adjusters and the reversing switch. A reversible motor 31 drives a main shaft 12 through gearing and a clutch 33, the tap-changing ratio adjusters 4, 5, 6, 7 being driven by the shaft through any suitable means (e.g. Geneva gears) in known manner. Initial rotation of the shaft 12 from the neutral position (shown in the Figure) causes the layshaft 29 to rotate a cam-shaft 25 through cascaded Geneva gears 28, 27, 26 so that one or other of the transfer switches 20, 22; 21, 23 is opened after a few degrees rotation of the cam 24. Thus the necessary change of transformer connections is made before any step has been made by the ratio adjusters. At the end of a sequence of operations of the ratio adjusters the cam 39 operates one or other of the limit switches 37, 38 to stop the motor, an additional safeguard being provided in the form of a clutch 33 which disconnects the shaft 12 from the motor 31 should the limit switches fail. A reversing switch 15 is provided to reverse the connection of the winding 2, but since it may be operated at any time during the initial half revolution of the ratio adjusters 6, 7 it may be of the slow operated type and be driven from the drive for the ratio adjusters 4, 5. After the initial movement of the shaft 29 to operate the transfer switches, further movement of the shaft causes the transfer switches to open correspondingly more as the voltage between the lines 16, 17 increases.