Devices to measure Insulation level between a live system and ground.

An insulation monitoring device circuit monitors the un-grounded system between an active phase conductor and earth. It is intended to give an alert (light and sound) or disconnect the power supply when the resistance between the line and ground drops below a set value, usually 50 kΩ (sample of IEC standard for medical applications). The main advantage is that the un-grounded or floating system allows a continuous operation of important consumers such as medical, chemical, military, etc. Most monitors work by injecting low level DC on the line and detecting.

Some monitors are capable of handling VFD’s (Variable Frequency (Speed) Drives) through immunity to the DC feedback from the VFD’s. Insulation monitoring device circuit detects deteriorations of the insulation level at an early stage and in a completely safe and reliable way. This effective device provides information for preventive maintenance in advance, and also prevents shock hazards and ensure high system safety and property protection.