GB549746A - Improvements in and relating to electric meters - Google Patents

Abstract

549,746. Supply meters. BRITISH THOMSONHOUSTON CO., Ltd. Sept. 19, 1941, No. 12044. Convention date, Sept. 21, 1940. [Class 37] Side thrust on the bearings is reduced by arranging the driving and braking magnets in the same plane or in parallel planes on the same side of the spindle. The driving and braking magnets may be incorporated in a single structure as shown in Fig. 6. The E-shaped voltage core 26 and U-shaped current core 28 are held in fixed relation between a pair of non-magnetic side plates, between which are also clamped the lower ends of two small permanent braking magnets 34, 35. The magnetic circuits of the braking magnets are completed by U-shaped laminations 37, 38 which may be, as shown, integral with the voltage magnet laminations. Between the current magnet and the brake magnets are gaps 50, in which are placed non-magnetic clamping bolts or rivets. The permanent magnets 34, 35 are preferably arranged with their upper ends of the same polarity and are surrounded by copper bands 51 to prevent demagnetization. The brake magnets are of high coercive force material, for example, as described in Specifications 179,306, [Class 82 (i)], 423,897, 423,994 and 424,746, [all in Group II]. The current winding 27 consists of a single turn. The rotor may be magnetically suspended by the repulsion between a disc-shaped magnet fixed to the lower bearing and a similar magnet carried by the lower end of the shaft. The braking torque is adjustable by screws 52 of magnetic material forming magnetic shunts. Alternatively the brake magnets may have axial threaded holes into which soft iron screws are fitted. Two similar complete driving and braking units may be arranged on opposite sides of the spindle for measuring polyphase energy. The armature disc may be built up of overlapping insulated sectors. In a modification, Fig. 11, the driving and braking fluxes cut the meter disc between the same pole pieces, the permanent magnets 71, 72 magnetically connecting the voltage core 65 and the current core 68. In another construction the driving and braking magnets are arranged along the same radial line of the armature and on the same side of the shaft but at different distances therefrom. The brake magnets consist of two horseshoe magnets on opposite sides of the disc with their poles facing one another, the magnets being arranged outside the driving magnet. Specifications 247,248, [Class 37], 462,443 and 516,128 are referred to.