GB622216A - Improvements in or relating to on-load tap-changing electric switches - Google Patents

Abstract

622,216. Regulating switches. BEDGGOOD, V. March 5, 1946, No. 6869. [Class 38(v)] An on-load tap-changing switch comprises a rotary contact which engages the inner surface of a cylindrical fixed contact unit consisting of a number of insulated conducting segments which are held in position by inwardly acting radial forces produced by clamped external rings. The rotary contact comprises a pair of spring- pressed brushes and each conducting segment of the fixed contact unit is provided with an insert of insulating material situated towards one end of the segment, adjacent segments having the inserts at their opposite ends. The arrangement is such that as the brushes are rotated, one brush rests on the conducting part of a segment while the other brush rests on the insert, the first brush then resting on the insert of the next segment and the second brush engaging the conducting part. Current is conveyed to the brushes by means of a slip ring and through the centre tapping of a resistance, the ends of which are joined to the brushes. Fig. 3 shows a switch in section in which a is one of a number of segments arranged cylindrically. Each segment is formed with two oppositely inclined surfaces b which are engaged by a pair of correspondingly shaped rings c, d from which they are insulated by rings e. The rings c, d are clamped and drawn together by bolts and nuts f, thus producing an inward radial pressure on the segments a which are thus held rigidly in position. Adjacent segments are provided with insulating inserts g. The movable contacts of two brushes n mounted on pivoted holders carried by a rotary member h, whose spindle i is mounted in a spider j attached to the ring c. The brushes are connected to the ends of a resistance o, the centre point of which is connected to a slip ring against which a plunger p bears, which is connected to an external circuit. Each segment a may be joined to a tapping point on a transformer &c. The switch may operate in oil and when operated in air the spindle i may be arranged vertically to assist cooling by convection.