GB190601487A - Improvements in or relating to Electricity Meters. - Google Patents

Abstract

1487. Blßthy, O. T. Jan. 19. Energy meters of the induction-motor type. To reduce e errors due to variations of pressure and frequency, the magnetic field of the shunt electromagnet is arranged to vary more than in proportion to the current passing through it. Electro-magnets may be used in place of permanent magnets for braking purposes by so arranging them in connexion with the shunt electro-magnets that variations of pressure produce no alteration in the field of the brake magnets but a more than proportional alteration in the driving-magnet. The increased effect in the shunt magnet is obtained either by the use of a magnetic shunt Ns, Fig. 1, with a reduced portion x, which is saturated at the lowest pressures, or by the use of an independent inductance coil with a similar reduced part in its core, connected in series in the pressure circuit. In the arrangement shown in Fig. 7, the core of the shunt electromagnet is divided into a driving-part N and a braking-part B, in the latter of which are reduced portions x, so that, while the braking field remains constant, variations are concentrated in the driving portion. A similar result is obtained by using independent braking and driving electro-magnets, connected in series in the pressure circuit, the brake magnet having reduced portions and the driving-magnet an ordinary core, or a core with a magnetic shunt as shown in Fig. 1, to increase the effect. The brake electro-magnet may also be connected in parallel with the driving electromagnet, and in this case it is either connected in series with an inductance coil or is provided with horns forming a magnetic shunt to absorb the variations. The reduced parts of the cores may be formed by piercing the laminations with holes, or by interrupting some and continuing others as shown in Fig. 4 ; in addition, the remaining plates may be pierced by holes d as shown.