Actual Loading Method

This method is employed commonly for testing of single phase meters within laboratory. On a meter testing bench that is equipped along with several taps to facilitate meter testing at variant load conditions. The load is provided through standard resistance or lamps obviously power factor is unity.  Load adjustments are completed in steps of 1/10th of full load at unity power factor. It is significant to note in this connection in which consumer's power factor varies from 0.5 to unity (or 0.85). Thus, meter must be calibrated at 0.5 PF. To achieve this condition, the current coil is energized through R phase and voltage coil through Y phase and the polarity of pressure coil is reversed. Under these conditions, PF becomes 0.5 since of 120 degree phase shift among voltage and current vectors.