MEGABRAS MD-1035e Guia Del Usuario página 12

4.9. Dielectric absorption index (DAI)
For this kind of tests, the apparatus should be connected, applying high
voltage to the sample for 1 minute (60 seconds). After this period, the
operator must press the Q key to read the absorption index value on
the display. If this key is pressed before the 1-minute period has elapsed,
the display will show DAI = - - -.
The Dielectric Absorption Index is the ratio between the insulation
resistance value measured after 60 seconds and the value measured
after 30 seconds. This value is useful to determine whether it is necessary
to perform preventive maintenance on the coils (transformers, engines
and motors, generators, etc.).
4.10. Polarization index (PI)
For this type of tests, the equipment must be connected and apply high
voltage to the sample for 10 minutes. After this period, the operator must
press the X to display the PI value on the equipment display. If the key
is pressed before the 10-minute period has elapsed, the display will show
PI= - - -. The polarization index is the ratio between the insulation
resistance value measured after 10 minutes and the value measured after
1 minute.
The polarization index is useful to determine whether it is necessary to
perform preventive maintenance. In addition, it is useful to detect any
insulation resistance wear and tear due to the excess of dust, grease, or
else the action of chemical or physical agents, etc.
R
DAI
60 seconds
=
R
30 seconds
R
PI
10 minutes
=
R
1 minute
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