Device for measuring active and/or reactive component of AC current or AC power

摘要

A device for measuring the active component and reactive component of AC current or AC power comprising a first detector detecting AC voltage of an AC circuit, a second detector detecting AC current flowing through the AC circuit, a phase shifter shifting the phase of the detected AC voltage by &pgr;/2, first switch selectively transmitting one of the detected AC voltage and the phase-shifted AC voltage, a signal generator generating a pulse signal lasting over a selected one half cycle of the two opposite half cycles constituting one cycle of the detected AC voltage transmitted through the first switch, a second switch responsive to the pulse signal to permit transmission of an AC voltage corresponding to the detected AC current, and a circuit computing the active or reactive component of the root mean square value of the AC current or power of the AC circuit on the basis of the AC voltage permitted to transmit through the second switch thereby providing an output signal representing the result of computation.