MEASURING CIRCUIT FOR INSULATION RESISTANCE VALUE

摘要

PURPOSE:To enable measurement of an insulation value of each part of an electric system while discriminating the same, by providing a resistance circuit consisting of a plurality of serial resistors between a P-side circuit and an N-side circuit of a DC electric system and by providing a polarity discrimination circuit between the intermediate connection point of the resistance circuit and an earthing point. CONSTITUTION:A resistance circuit 5 wherein a resistor R1 and a resistor R2 are arranged serially is connected between a P-side circuit 1 and an N-side circuit of a DC electric system. Moreover, a polarity discrimination circuit 6 wherein rectifying elements 61 and 62 are connected in reversely parallel is connected to the intermediate connection point P of the resistance circuit 5 and an earthing point Q. Currents flowing through the aforesaid rectifying elements 61 and 62 are detected by current detection circuits 7 and 8 respectively. In these circuits 7 and 8, current detecting resistors R3 and R4 are connected to the elements 61 and 62 respectively and voltages v1 and v2 at both ends of these resistors R3 and R4 are detected by voltage detection circuits 72 and 82 respectively. Currents I1 and I2 flowing through the resistors R3 and R4 are operated by operation circuits 72 and 82 respectively. I1 and I2 thus obtained and a line voltage signal V between the circuits 1 and 2 are sent to an insulation resistance value operation circuit 10, which judges the presence or absence of inferior insulation in each part of the electric system and operates an insulation value thereof.