Direct Reading Ratio-Error Sets for the Calibration of Current Transformers

Four different direct reading ratio-error sets, capable of generating measured complex fractions of an input reference current to a nominal accuracy of 1 percent of reading for such applications as current-transformer calibration, are described and analyzed. Construction and performance details for actual sets with 3 or more digit resolution in both direct and quadrature components from 0.1 parts per million to 10 percent of input currents up to 10 amperes at 50, 60, and 400 Hz, are given.