Answer / kapil mishra

PI is a variation of the IR test. It is the ratio of IR
measured after voltage has been applied for 10 minutes (R10)
to the IR measured after one minute (R1), i.e.

PI = R10/R1
Low value of PI indicates that the winding may have been
contaminated with oil, dirt etc or absorbed moistures. In
the test, a relatively high DC voltage is applied between
the copper conductor and the stator or rotor core usually
between the winding and ground as the machine core & body
are grounded)

Answer / 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

Answer / sridhar

It is the ratio of Insulation Resistance value of 1st
minute and 10th minute for any Electrical equipment.
Equipment is said to be sound if the ratio is greater than
one.

Answer / santhoshkumar

The ratio between IR value for 10 minutes to 1 minute.
It proves the healthiness of the insulation. Best value
will be above 1.2

Answer / rajpalsing rajput

It is the ratio of IR value at 10 min to the IR value at 1
min.It is measure of condition of insulation system wether
it is clean or dirty.If it is greater than 2 indicat the
good condition of insulation system and if it is greatore
than 6 indicate that insulation system is thermally degrade.

Answer / 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.

Answer / karthikeyan

Polarisation intex test is used for find out the IR value at
a particular temperature

how does high earth to neutral voltage affect electronic equipment?

0 Answers  

Is any AC drive(VFD) had a feature of DC injection braking? if available please mention the detail. i.e drive can supply braking torque when the motor in idle state.

0 Answers  

with help of neat sketch explain principle of TIG welding process

0 Answers  

how to calc. current for 5MVAR,50hz,33kv

1 Answers  

Advantage of 11KV ring main system with open point

1 Answers   Alam Group of Companies,

which metal is use in shunt

4 Answers  

cab we add capacitor bank with generator to improve power factor or not??????

1 Answers  

How much width of the land shall have to be left below the EHT line of 440 kv as per the rule. i am told that a corridor of 35 M width is to be left free below 220 kv line. please confirm

1 Answers  

How to design grid earthing

1 Answers  

what is the voltage between earth to neutral in lift.

0 Answers   SIPL,

what instruments used for measuring of inductance and capacitance.

2 Answers  

1.What will be stored in online ups EPROM IC?

0 Answers   IBM,