ELECTRICAL CIRCUIT ARRANGEMENT AND METHOD FOR COUPLING AN INSULATION MONITORING DEVICE TO AN UNEARTHED POWER SUPPLY SYSTEM

摘要

The invention relates to an electrical circuit arrangement and a method for coupling an insulation monitoring device (4) to an unearthed power supply system (2) via a coupling impedance designed as an ohmic resistance circuit (12) for each active conductor of the power supply system, the ohmic resistance circuit having an adjustable, variable resistance value and has a switch-off function for decoupling the insulation monitoring device from the mains and is designed as a bidirectional cascade, consisting of a series connection of two transistors (16a, 16b) arranged in mirror images, each with a diode (18a, 18b) connected in parallel, a controlled one being used to set the variable resistance value The resistance of the transistors is changed by a control circuit (30) and the switch-off function for decoupling the network is implemented by setting a maximum resistance value. 2nd