Interested to Buy Any Domain ? << Click Here >> for more details...
what is PI value and its significance for insulation
testing?
- 3 Answers
- 27369 Views
- I also Faced
- E-Mail Answers
Answer Posted / biju9cr
Knowing the polarization Index of a motor or generator can
be useful in appraising the fitness of the machine for
service. The index is calculated from measurements of the
winding insulation resistance.
Before measuring the insulation resistance, remove all
external connections to the machine and completely discharge
the windings to the grounded machine frame.
Proceed by applying either 500 or 1000 volts dc between the
winding and ground using a direct-indicating, power-driven
megohmmeter. For machines rated 500 volts and over, the
higher value is used. The voltage is applied for 10 minutes
and kept constant for the duration of the test.
The polarization index is calculated as the ratio of the
10-minute to the 1-minute value of the insulation
resistance, measured consecutively.
Polarization Index =
Resistance after 10 minutes/
Resistance after 1 minute
The recommended minimum value of polarization index for ac
and dc motors and generators is 2.0. Machines having
windings with a lower index are less likely to be suited for
operation.
The polarization index is useful in evaluating windings for:
* Buildup of dirt or moisture.
* Gradual deterioration of the insulation (by comparing
results of tests made earlier on the same machine).
* Fitness for overpotential tests.
* Suitability for operation.
| Is This Answer Correct ? | 46 Yes | 4 No |
Post New Answer View All Answers
how freewheeling diode improves the powerfactor
What does the a,b,c of 95a,95b,95c relays denotes?
We have given to 3phase supply to ups system & how can coming netural
what is harmonics? what are the factors it will depend upon
why occ characteristics of generator is also called as magnatization characteristics ?
why dc is used in control circuits for MV & LV switchgeras instead of ac
I have a situation to design sub-Distribution board/Panel meant for feeding power sockets. In the incomer CAN i Take TP MCCB with Neutral Link and All the outgoing feeders with to sockets with TP MCCB and Neutral Link? P.S : My System is IT Earthing
Define rise time.
What do you mean by Stimulastion Test in Diesel Genarator / Why & when it's conducted ?
why would amp draw on neutral wire be as much as amp draw on the hot leg.
What are the types of control system?
USE OF 8 WAY PAN ASSEMBLY
what is meant by 2 within a star in a voltmeter dial?
all interview questions with answers of ntpc (2000-2009
why constant voltage transformer should be start without load? and if started then what will happen?
