| 摘要 |
PURPOSE:To simply and highly accurately measure insulation resistance by applying square waves to a power line through an earth line for a transformer, detecting leaked current returned to the earth line and integrating the detected value at two integrating periods consisting of integer times the reference frequency of a commercial frequency components to execute arithmetic processing. CONSTITUTION:A square wave is formed through a commercial voltage circuit 4, voltage dividing transformer T02 and wave shaping circuit WS, and the shaped wave is divided by frequency divider DIV, applied to a voltage supplying circuit OS and then applied to power lines 1, 3 through an earth line EL. Leaked current returned to the EL is detected by a current detecting probe CD and integrated by integrators INTEG 1, 2 through an amplifier AMP at the integrating time of commercial frequency component periods TO, 2TO and the integration is ended by signals INT 1, 2. After weighting at resistors R1, R1/2, both outputs from the INTEG 1, 2 are subtracted by a subtractor SUB and stored in a holder consisting of a buffer amplifier and then voltage inversely proportional to insulation resistance is outputted through a low-pass filter (R2+C2). Thus the insulation resistance is simply and highly accurately measured. |
