A Technique for Calibrating Power Frequency Wattmeters at Very Low Power Factors

The application of a current comparator capacitance bridge to the measurement of the error of power frequency wattmeters at zero and very low power factors is described. The desired voltage, current, and power factor, leading or lagging, are established with a capacitive-type artificial load. The power factor is adjusted with reference to a loss-free gas-dielectric capacitor to within 1 × 10-5 or to an accuracy of 1 percent, whichever is greater, and voltage and current to an accuracy of better than 1 percent. Results of the measurements on representative commercially available electrodynamic and electronic wattmeters are given.