An experimental study of the effects of non-sinusoidal currents on the registration of induction watthour meters

It is known that the registration of the induction disk watthour meter (WHM) is sensitive to the waveform of the metered current. The authors report an experimental study to determine the registration errors of induction disk WHMs for three cases of nonsinusoidal current waveforms. These cases are: (1) full-wave, phase-delayed sine wave; (2) full-wave, phase-delayed square wave; and (3) full-wave, battery charger wave. In all cases the voltage to the WHMs was sinusoidal. Four WHMs were tested, two manufactured by Sangamo Electric Company and two manufactured by Duncan Electric Company. These instruments were connected for 120 V operation with a class current of 10 A. An electronic WHM was used as a standard for the tests. Registrations of the test WHMs exceeding the readings of the standard are considered to be positive errors. It was found that the nonsinusoidal currents resulted in WHM errors that were generally positive and as great as 7%. The error characteristics of the four WHMs were consistent.< >