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What is polarisation index value?.(pi value)
Simple & brief definition of polarisation index?..
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Answer Posted / v.senthilkumar - skpcl
The ratio between IR value for 10 minutes to 1 minute.
Formula (PI) = Resistance Value 10 Min after
start/Resistance value 1 Min after start. (IR 10min / IR
1min)
The recommended minimum values for PI are based on the
thermal class of the insulating materials and apply to all
insulating materials regardless of application per IEC
60085-01:1984. The PI test is not applicable to non-
insulated field winding. The recommended minimum value for
PI are as follows:
Class A Termal Class Rating = Min PI is 1.5
Class B Termal Class Rating = Min PI is 2.0
Class F Termal Class Rating = Min PI is 2.0
Class F Termal Class Rating = Min PI is 2.0
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