System for detecting alternating voltage and/or current.

摘要

A system for detecting a voltage and/or current of a single phase and/or polyphase alternating current comprises a sample-hold circuit for detecting and holding instantaneous values of a plurality of sampling points at a fixed time period of the alternating current as sampled values, respectively, a first calculation circuit for calculating the real part and the imaginary part of the Fourier coefficient with respect to a fundamental wave and/or component of positive-phase sequence of the alternating current to be detected from the plurality of sampled values thus held to separate the real and imaginary parts thus calculated to output respective calculated values thereof, and a second calculation circuit for further applying a predetermined calculation to the calculated values of the real and imaginary parts to thereby calculate and output the amplitude of the fundamental wave and/or component of positive-phase sequence of the alternating current. <IMAGE>