GB859044A - Improvements in or relating to electrical phase-shifting transformers - Google Patents

Abstract

859,044. Regulating switches. UNITED GAS INDUSTRIES Ltd. Aug. 16, 1957 [Aug. 17, 1956], No. 25279/56. Class 38 (5). [Also in Group XXXV] A three-phase phase shifting transformer has a winding arrangement with taps connected to points whose voltages are regularly displaced in phase over 360 degrees and a selector switch by which any three taps spaced mutually at 120 degrees may be simultaneously selected, fine adjustment over the phase range between adjacent taps being provided by three variable auto-transformers. Fig. 7 shows transformer windings fed at taps 1, 9, 17 from three-phase mains 66 having taps numbered 1 to 24 and a neutral centrepoint. The taps are connected to similarly-numbered contacts on three similar selector switches with groups of rotatable contacts such as 1R, 2R, 3R, respectively spaced at 120 degrees. Contacts 1R and 2R normally connect two adjacent contacts through slip-rings 19, 20 to the opposite ends of one of the auto-transformers 22, 23, 24 from movable contacts from which the phase-displaced outputs 67 are taken. Breaking of the output connections whilst a tapping switch is being rotated to the next pair of contacts is prevented by the connection of one of the taps through moving- contact 3R, slip-ring 21 and resistor 25 to one end of the associated auto - transformer. As shown in Fig. 1, the selector switches are formed by three plates 12, 13, 14 bearing the tapping contacts and the sliprings over which travel respectively angularly-spaced segmental arms 26, 27, 28 which are mounted on a spindle 16 and carry appropriately-spaced spring-biased contact-plungers 31. A pointer (not shown) mounted on the end of spindle 16, moves over a fixed graduated dial 5 to show the contact position selected. A similarly graduated dial 6 mounted on disc 45 is moved with the moving contacts of the autotransformer 22, 23, 24 through spring strip and lever connection 54 by a knob (not shown) on spindle 8 to indicate the value of the fine adjustment. Spindle 16 carrying the segmental arms is located angularly by the cooperation of spring-pressed insulating rollers 38 at the ends of insulating arms 36 carried by the spindle with extensions of the tapping contacts or intermediate pins. Alternatively the contacting extensions may be insulated when the rollers are metal. The selector switches are mounted on four pillars with upper and lower frame plates 10, 15 carrying the bearings of spindle 16. On plate 10 are also mounted three pillars 42 carrying frame-plates 43 and a shaft 8 with the auto-transformers 22, 23, 24. By a knob on shaft 9 mounted on plate 10 annular scale 7 is rotated about scales 5 and 6 through friction gearing 63, 64, 48. This scale is graduated in degrees and cosine values. The whole arrangement which may be used for testing without meters is enclosed in a casing and mounted on castors, Figs. 3, 4.(not shown).