What is the absorption ratio of an insulation resistance tester and what is its function?

Absorption ratio is an important indicator used to evaluate the insulation performance of electrical equipment, especially in devices such as transformers and motors. It refers to the ratio of insulation resistance values measured at two different time points after applying a DC voltage. The most commonly used absorption ratio is the ratio of insulation resistance measured at 60 seconds and 15 seconds after applying voltage. Taking transformers as an example:
Absorption ratio greater than 1.3: indicates that the insulation material is in good condition.
~Between 1.0 and 1.3: indicates that the insulation material condition is average, and there may be slight aging or moisture.
~Less than 1.0: indicates that the insulation material may be severely damp or have defects, requiring further inspection and treatment.