| 摘要 |
PURPOSE:To obtain the quantity of the alternating currents of threefold harmonic waves synchronizing with a fundamental harmonic by using a comparatively simple means by a system wherein the quantity of three phase alternating currents being detected is converted into the quantity of sine wave alternating currents and that of cosine wave alternating currents, and a specified computing containing square, etc. is conducted on the basis of these quantities. CONSTITUTION:The quantity of three phase alternating currents is detected, and converted into the quantity of sine wave alternating currents and the quantity of cosine wave alternating currents, and a specified computing is conducted on the basis of the quantities of these alternating currents. For example, each instantaneous value of three phase currents from a frequency converter 1 which is feeding electricity to a load 3 is detected by means of current detectors 4-6, while these signals are inputted to a three phase to two phase converter 7, and the quantity of sine wave alternating currents id and the quantity of cosine wave alternating currents iq are put out. The signals are inputted to a vector analyser 8, alternating current signals A=sin<2>omegat and B=sinomegat with amplitude in unit quantity are put out, and the signals of C=(3-4sin<2>omegat)Xsinomegat=sin3omegat are obtained through a counter 9, an adding and subtracting instrument 10 and a multiplier 11. |
