| 摘要 |
PURPOSE:To enable a stable detection of a second high harmonic component among rush current components of a transformer with a high sensitivity and free from variations in the frequency in the system by defining the alternate current of a reference frequency. CONSTITUTION:This system is equipped with a double frequency circuit 3 for forming the level of alternate current of a reference frequency equal to that of higher harmonic components contained in an A.C. input 6, a BPF 4, a circuit 9 for analog function computation of the reference A.C. level and an A.C. input 8, an LPF 10 for taking out D.C. components from outputs of the computation. Only the components the same in the frequency as A.C. components as reference are detected among higher harmonic components contained in the A.C. input 6 as D.C. level proportional to the magnitude thereof. |
