Patent GB-453245-A (GB)
Title: Improvements in arrangements for making test measurements of alternating currents
IPC: G01R1/30
Filed: 1935-07-30
Abstract: 453,245. Current, pressure, capacitance, and phase - difference measurements. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. July 30, 1935, No. 21650. Convention date, July 30, 1934. [Class 37] An arrangement for making test measurements or analyses in respect of a portion of any desired length or phase position of a cycle of alternating current or potential comprises a double coil zero instrument DN of the rotating coil type, of which one rotating coil SM, constituting the testing winding, is connected with the testing circuit through one or more externallycontrolled rectifiers, while the other rotating coil SK is connected in a direct current compensation circuit which is connected through a further rectifier GK to the source of alternating current supplying the testing circuit. In the arrangement shown in Fig. 1, for measuring dielectric losses of condensers or the like, the condenser CX to be tested is connected up with a standard condenser CN and resistances R<1>, R<11> in a bridge, as shown, and the winding SM is connected across the diagonal of the bridge in series with a high ohmic resistance RM and a vibrating contact rectifier GM controlled by a phase shifter Ph. The bridge is balanced with respect to its capacity and resistance values, and the phase shifter is adjusted so that only the loss angle component of the potential arising across the diagonal of the bridge is applied to the coil SM. The winding SK is connected across a resistance wire RS with a sliding contact connected through the rectifier GK and a resistance RG across a resistance RN in the testing-circuit. The sliding contact is adjusted until no deflection is obtained on the instrument DN; the portion r of the resistance RS in the circuit is then a measure of the loss angle of the condenser CX. Capacitative differences between CX and CN can be determined with the same circuit arrangement by rotating the phase shifter by 90‹. In the arrangement shown in Fig. 2, the invention is applied to the point plotting of alternating current curves by connecting two externally-controlled rectifiers G1, G2 in series, the rectifiers being excited through a common phase displacer Ph and series resistances R1, R2, one of which is shunted by a condenser CR, so that the closing periods of the rectifiers are displaced with respect to each other by slightly more or less than a half period, as described in Specification 382,464. A condenser CM connected to the testing winding SM of the instrument DN is charged to a voltage corresponding to the instantaneous value of the current at the moment when both rectifiers are closed. The compensating winding SK is connected to a resistance RS supplied through a rectifier GK from the same source as the current under test ; when the instrument DN is at zero, the portion r of the resistance RS in circuit is proportional to the instantaneous value of the current. By adjusting the phase shifter Ph a series of instantaneous values of the current corresponding to different phase positions can be determined, from which the alternating current curve can be plotted.