GB640400A - Improvements in and relating to electric induction meters - Google Patents

Abstract

640,400. Supply meters. OBORNYAK, L. Dec. 31, 1947, No. 35380. Convention date, May 3, 1943.. [Class 37] In an induction watt-hour meter the overload shunt comprises a bridge of ferromagnetic material across the limbs of the current magnet and at least one pole projecting from the bridge and above the surfaces of the current magnet poles and wherein saturation occurs subsequently to saturation of the bridge. In Fig. 1, the bridge 3 separated from the current magnet 1 by diamagnetic inserts 5 possesses pole surfaces 11 above the level of the current magnet pole surfaces 8 with the voltage magnet pole surfaces 10 nearer 11 than 8. The reluctance of the magnetic path including the air gaps between 8 and 10 is greater than the path including the poles 11. At a predetermined meter overload the bridge 3 saturates and then as the load progressively increases poles 11 gradually saturate so that there is an extended range of compensation. Fig. 3 shows a laminated shunt or bridge 3 insulated from the current magnet 1 by diamagnetic inserts 5 and magnetized directly in that legs 4 project into the current coils 2 which means that shunt poles are formed independently of the current magnet 1. In both Figs. 1 and 3 with the next flux increment after saturation of the bridge 3 the poles 11 attain a magnetic potential exceeding that of the current magnet poles 8. Fig. 2 employs a U-shaped shunt 3 with projecting bent-over pole 11. The legs 4 of the shunt extend into the current coils 2 and are secured to the magnet 1 with interposed laminations 3<SP>1</SP> and finally diamagnetic inserts 5. The shunt pole adjusted to the required position above the poles 8 attains a magnetic potential exceeding that of the poles 8 with saturation complete in 3, 3<SP>1</SP>. A construction utilizing a single projecting shunt pole as in Fig. 2 may be employed with the shunt magnetized inductively by the current magnet as in Fig. 1. In Fig. 4 (not shown) the shunt has two projecting poles and legs fitting into slots in the current magnets. Perforations 12, 13, Figs. 2 and 3, may be formed in the bridge to control the saturation point on the load curve. The Specification as open to inspection under Sect. 91 states that the pole surface 11, Fig. 2, may be level with the current magnet pole surfaces 8. This subject-matter does not appear in the Specification as accepted.