Electronic Three-Phase Four-Wire Power-Frequency Converter With High Accuracy Over a Wide Range of Use

This paper describes a new type of power-frequency converter with an electronic measuring device. It is of the three-phase four-wire type and was developed in the Physikalisch-Technische Bundesanstalt (PTB) especially for the precision measuring of electrical energy in high-voltage circuits. It has an accuracy of 10^-3 over a current range of 1: 100. The measuring elements use the time-division principle. The wide current range is achieved by commutating the charging current for the integrating circuit. The running (indication) of the instrument with no load is eliminated. The specifications are much better than those of a high-precision rotor-type meter of class 0.5 (Recommendations of the International Electrotechnical Commission-IEC).