Insulation resistance testing

Why is insulation resistance testing important?

Although the fundamental approach to insulation resistance testing is the same as for withstand voltage testing, the two types of testing are distinguished by the following differences:

•    The point of insulation resistance testing is to measure the resistance value at a certain test voltage, not to gauge the strength of the insulation. By contrast, the point of withstand voltage testing is to check dielectric strength to see whether an insulation breakdown will occur.

•    Whereas most withstand voltage testing is carried out with an AC current, insulation resistance testing, which measures only the resistance component, uses a DC current.

How to test insulation resistance

Insulation resistance testing locations: 
Positive electrode and externally exposed metal surfaces

Insulation resistance test conditions: 
Output voltage of 500 V, judgment reference of 5 MΩ or greater, etc.

Reference: JIS C 8711, JIS C 8712