What is polarisation index value?.(pi value)
Simple & brief definition of polarisation index?..

Answer Posted / md. robiul islam

Polarization Index is an indicator which gives an idea of
the cleanliness of the windings. It is a ratio of the
Insulation Resistance Measured for 10 minutes to the
insulation resistance value measured after 1 minute. Since
it is a ratio; it does not have any units.

Polarization Ratio = Insulation Resistance after 10 minutes/
Insulation Resistance after 1 minute

The Polarization Index should be above 2.0 to be
permissible. Machines having PI below 2.0 cannot be operated.

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