POWER FUNDAMENTAL WAVE PHASE DETECTION DEVICE

PROBLEM TO BE SOLVED: To detect the phase of a power fundamental wave in real time for following. SOLUTION: A programmable timer 19 generates a trigger with a timing where one wavelength section of the current or a voltage of a power fundamental wave is divided into N equal portions, the power fundamental wave being inputted to an A/D converter 1 is sampled at a trigger timing, obtained sampling values are multiplied by sin (2 nπ/N) and cos (2 nπ/N) values corresponding to a phase (n) and are integrated for a wavelength section immediately before, and an value being obtained by multiplying each of both integrated values by 2/N is outputted as a coefficient A of a sin term of the current or the voltage of the power fundamental wave and a coefficient B of a cos term, thus monitoring the fluctuation of the phase from the both coefficients.