GB309128A - Measuring arrangements for measurement of ratio of transformation and phase angles of voltage and current transformers - Google Patents

Abstract

309,128. Slavik, J. April 5, 1928, [Convention date]. Inductances and phase-differences, measuring; stopping devices for motor meters.-For measuring the transformation ratio and phase angle of transformers, two meters I, II, Fig. 1, are employed, each having two driving systems. In series with the pressure coils of the driving systems S1, S2 are condensers C and resistances R so adjusted that the currents in these pressure coils are in quadrature with the currents in the pressure coils of the systems C1 C2. The current coils of the four driving systems are supplied from an auxiliary transformer T, the primary winding being connected between one phase x of a three-phase system and a variable tapping on a resistance W connecting the other two phases y, z, in order to permit adjustment of the phase of the current supplied to the current coils. In order to measure the transformation ratio of a potential transformer Me, the secondary winding is connected to the pressure winding C1, the remainder pressure windings S1, C2, S2 being connected in parallel to the secondary winding of a standard transformer Ne. The phase of the current in the current coils is adjusted until the meter I is at rest when the transformer Me is switched off. The transformer Me is then switched in and readings are taken of the number of rotations of both meters in the same time; their ratio is the same as that of the transformation ratios of the transformers Me, Ne. To measure the phase angle, the secondary winding of the transformer Me is connected to the pressure winding S1, the remaining pressure windings, C1, C2, S2 being connected in parallel to the secondary winding of the standard transformer Ne. The phase angle can be calculated from readings of the rotations of the meters I, II. Current transformers may be similarly tested, the pressure circuits of the meters being connected in parallel to a voltage of adjustable phase, one current coil being connected to the secondary windings of the transformer to be tested, and the remaining current coils being connected in series with the secondary winding of the standard transformer. Fig. 3 shows a stopping device for the meters I, II, by means of which they can be simultaneously released to facilitate counting the rotations. Stops R1, R2 are carried by a rod H, by rotation of which they are simultaneously removed from the path of projections A1, A2 on the discs. The whole of the apparatus is preferably mounted in one case.