| 摘要 |
PURPOSE:To measure insulation resistance which is compensated the influence of earth resistance by simple constitution by inputting one measurement signal to an earth line, and further substituting this measurement signal with a commercial frequency voltage. CONSTITUTION:An AC signal voltage V1sinomega1t of frequency f1 is inputted directly to cable runs L1 and L2 through the earth line LE of a transformer T, a leak current component I1(t) of f1 which is fed back to the earth line LE is extracted BP1, and the voltage e(t) between one optional point P on the prolongation of the cable run L2 and the ground E3 is detected by an amplifier AMP and a filter BP2 which passes components of frequency f1. Further, a low-pass filter LP extracts a DC voltage D from the output obtained by inputting the voltage e(t) to the other input terminal of a multiplier MULT1. Further, the voltage (d) obtained by inputting the output of the filter BP2 to a rectifying circuit DET is inputted to a biquadratic circuit QD to obtain a voltage d4. Then the output of the filter LP and the output of the biquadratic circuit QD are inputted to a divider DC to measure the insulation resistances of the cable runs L1 and L2.
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