GB561421A - Improvements in electric meters - Google Patents

Abstract

561,421. Supply meters. BRITISH. THOMSON-HOUSTON CO., Ltd. Jan. 21, 1943, No. 1054. Convention date, Jan. 23, 1942. [Class 37] In an induction motor meter the brake magnets are so arranged that the forces produced by their reaction with the eddy-currents produced by the driving magnets cancel out, thereby preventing vibrations of the disc. The meter shown in Fig. 1 is provided with a voltage core 10, voltage coil 11, current core 12, and current coil 13 driving a disc 15. C-shaped permanent brake magnets 17, 18 are arranged as shown. Fig. 3 is a plan of the disc 15 showing the distribution of the eddy currents 20 produced by the voltage flux. The brake magnets 17, 18 are positioned as shown so that tHe forces F produced by the interaction of the braking field with the eddy currents 20 are equal and opposite. In an alternative construction each brake magnet system consists of a pair of horseshoe permanent magnets 22, 23, Fig. 5, one on each side of the disc 15. These brake magnet systems are located symmetrically on opposite sides of a diameter of the disc passing through the centre of the driving magnet as shown at 24, 25, Fig. 4, so that the forces FN, FS balance. Specifications 516,128 and 549,746 are referred to. The Specification as open to inspection under Sect. 91 states also that the arrangement of the brake magnets may be adjusted to take into consideration the forces produced by their interaction with the current flux eddy currents. This subject-matter does not appear in the Specification as accepted.