| 摘要 |
PURPOSE:To measure an active power and a reactive power in a wide range by arithmetically processing the voltage signal and the current signal with a Fourier transformation. CONSTITUTION:An analog voltage signal 1 in a system to be measured is inputted to an A/D converter 3 through a sample-and-hold circuit 2, then inputted to a high speed Fourier transform device (FET) 4 in the manner of making the real and imaginary parts of the output digital signal to be zero. The real and imaginary parts resulted from the Fourier transformation are inputted to multipliers 5,8 and 16,14 respectively, and each output of the multipliers 5,8 are subtracted in a subtracting device 6. Also an analog current signal 10 in the system to be measured is similarly processed in order of the sample- and-hold circuit 11, A/D converter 12, FFT 13, and the real and imaginary parts resulted from the Fourier transformation are inputted to the multipliers 14,16 and 5,8 respectively, and each output of the multipliers 14,16 are added in an adding device 17. Then, by means of integrating the output of the subtracting device 6 in an integrating circuit 7, the active power data 9 are obtained, and the reactive power data 18 can be obtained if the output of the adding device 17 is integrated in the integrating circuit 15. |
