| 摘要 |
PURPOSE:To calculate a frequency to be extracted and the levels of an effective and an ineffective component by multiplying a quantity to be measured by sine waves and cosine waves of three phases as units and further multiplying the DC component of the sum value by sine and cosine waves as units. CONSTITUTION:Sine wave generators 11-13 of respective phases and cosine wave generators 21-23 of respective phases generate a three-phase sine wave and cosine wave signals synchronized with a power source among angular velocity components of frequency to be extracted. Those values are multiplied by the quantity to be measured through multipliers 311-313, and 321-323, products of the sine waves and cosine waves are summed up 41 and 42, and their DC components are detected 51 and 52. Further, the outputs of DC detectors 51 and 52 are supplied to a multipliers 611-613, and 621-623, which multiply them by the outputs of the generators 11-13 and generators 21-23 to calculate effective and ineffective component of frequency to be extracted which are contained in respective phase current or voltage waveforms. Those effective and ineffective components are summed up 71-73 by the phases to find the levels and phases of frequency components to be extracted.
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