How to calculate minimum insulation resistance requirement for any electrical equipment.

As an electrical engineer we all know about IR test or insulation resistance test, what is it and why we need to test.

After completing an insulation test as per rules and regulation now that we have the IR test result the next confusing factor stands in front of us that- we got the result, is it satisfactory or not. This decision making is vital as if some wrong happens it will a loss in both ways.

You are either marking a good equipment as bad or marking a bad equipment as good -Wrong decision of IR test requirement for an equipment.

Calculate minimum insulation resistance test result requirement for an equipment:

The required formula is –
R=1+V, Here R=resistance in mega ohm(MΩ) , V= equipment rated voltage in KV.

So if we like to check a machine rated voltage is 11 KV, the minimum tolerated insulation resistance will be R=1+11=12MΩ, and for a motor with 220 voltage rating the IR value will be R=1+.220=1.2MΩ.
This data I have got from the official manual of Fluke.

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