Digital power factor meter based on non-linear analogue-to-digital conversion

ABSTRACT The paper describes the development of an electronic power factor meter to replace the conventional electrodynamic type. The design is based on a non-linear analogue-to-digital converter (NL-ADC). Each of the alternating voltage and current signals is applied to a zero-crossing detector and then exclusive OR-ed and filtered to obtain a DC signal proportional to the phase angle between the voltage and current. The NL-ADC introduces a digital number proportional to the square and fourth powers of this DC signal. The power factor is then obtained by using only three terms of Maclaurin's series of the cosine function. A microprocessor-controlled analogue-hybrid computer type EAI-1000 is used in the circuit design which has highly efficient analogue devices.