Insulation Test

The insulation test (further known as insulation resistance test) is a high voltage test that determines the insulation resistance between two points at a unit under test (UUT).

 

It is mostly performed by using high voltage direct current (HV-DC test) since the insulation resistance does not depend on the polarity of the measurement voltage.

 

Even though a UUT can show a really high insulation resistance, it may happen that its electric strength is limited. Therefore, it is tested in a separate test phase, usually with high voltage alternating current (HV-AC test).

 

Commonly a short test should rule out a short circuit before start.

 

During slew rate, waiting time and measurement time, the system is monitored for a potential arc. In case it occurs, the test step will be stopped and logged as FAIL.

 

Otherwise, the floating insulation current is measured in equidistant time intervals and averaged. At the end of the measurement time, the insulation value is calculated from the measured current and programmed voltage, logged and the UUT discharged.

 

In case a manufacturer is ISO 9001 certified, often test results need to be logged and saved in a database for retracing and for further analysing in statistics.