Enter the insulation resistance after 10 minutes and the insulation resistance after 1 minute into the Calculator. The calculator will evaluate the Polarity Index. 

Polarity Index Formula

PI = R10 / R1

Variables:

  • PI is the Polarity Index ()
  • R10 is the insulation resistance after 10 minutes
  • R1 is the insulation resistance after 1 minute

To calculate Polarity Index, divide the insulation resistance after 10 minutes by the resistance after 1 minute.

How to Calculate Polarity Index?

The following steps outline how to calculate the Polarity Index.

  1. First, determine the insulation resistance after 10 minutes. 
  2. Next, determine the insulation resistance after 1 minute. 
  3. Next, gather the formula from above = PI = R10 / R1.
  4. Finally, calculate the Polarity Index.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

insulation resistance after 10 minutes = 2.5

insulation resistance after 1 minute = 3