Patent GB-209716-A (GB)
Title: Improvements in and relating to electromagnetic relays and measuring apparatus
IPC: G01R5/14
Filed: 1923-11-10
Abstract: 209,716. Measurement, Ltd., (Assignees of Compagnie pour la Fabrication des Compteurs et MatÚrial d'Usines Ó Gaz). Jan. 12, 1923, [Convention date]. Void [Published under Sect. 91 of the Act]. Electromagnetic switches. - Relays or power meters are constructed so as to give a linear function of several electrical powers consumed in circuits traversed by currents of the same or different frequencies, one of which mav be a direct current., and in which the movable parts are subjected to the action of a total couple equal to the difference of two couples, each of which is proportional to the square of a linear function of the voltages and currents in the various circuits. An electromagnetic instrument is shown in Fig. 1, in which soft iron members 5, 10 are mounted on the same shaft 11, the member 5 being influenced by the magnetic field due to coils 1 - - 4 and the member 10 by that due to coils 6 - - 9. The couples exerted on the members 5, 10 are proportional to the square of the fluxes acting on them and are opposite in direction. The coils 1, 6 are connected in series in one circuit, the coils 2, 7 being connected across this circuit. Similarly the current coils 4, 9 and pressure coils 3, 8 are connedted to the second circuit. The coils 1 - - 4 are so wound that the magnetic flux acting on the member 5 is proportional to the sum of the currents plus the difference of the pressures in the two circuits, and the coils 6 - - 9 are so connected that the flux acting on the member 10 is proportional to the sum of the currents minus the difference of the pressures. The torque on the axle is then dependent only on the difference of the powers in the two circuits. In the case of a relay, an adjustable spring is employed to determine the value at which it operates. In the case of a wattmeter, pole-pieces shaped as shown in Figs. 4 and 5 are employed. When no current flows through the coils 3, 4, 8, 9, a simple wattmeter is obtained. If the coils 2, 7 are connected so as to be traversed by a current in quadrature with the pressure, the instrument gives the value of the reactive power. The coils 1, 6 may be connected in series across the secondary of a current transformer, and the coils 2, 7 in series with the secondary of a pressure transformer. Alternatively the coils 1, 6 may be connected across a shunt in the main circuit, and the pressure coils 2, 7 directly across the mains or in series with a resistance. Each pair of coils 1, 2 and 6, 7 may be replaced by a single coil traversed respectively by a current proportional to the sum and difference of the voltage and current. Differential or compound wattmeters or relays of the wattmeter or sine type may be constructed by so connecting the coils that the couples acting on the axle either oppose or assist one another. In order to obtain the sum or difference of the powers supplied in two circuits fed from one -source, i.e. when the voltage of the two circuits is the same, the current measuring part in simple wattmeters or relays is replaced by double windings giving the sum or difference of the currents in the two circuits, i.e. the windings 1, 6, Fig. 1, are traversed by the two currents acting oppositely in order to obtain the difference of the powers.