Baker D30R, User'S Manual & Operating Instructions

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D30R Users Manual
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Do Not Touch Test Leads while test is in Progress!
71-023 Rev C 5/8/2007
Unfortunately, most the insulating materials developed recently (last 20 years)
do not easily polarize. For example the newer inverter grade wires and epoxy
resins do not readily polarize. As recommended in IEEE 43-2000, if the one-
minute insulation resistance is greater than 5000Mohms, the PI measurement
may not be meaningful.
To address the situation where the PI may not be meaningful, the Dielectric
Absorption (DA) is widely used instead. The DA is the IR value at 3 minutes
divided by the IR value at 30 seconds. The motivation for even doing the DA
test is to reduce the test time to 3 minutes instead of 10 minutes for the PI test
when the PI test may not be worthwhile. To date there are no accepted values for
the DA. However, some usefulness can be obtained by trending the DA value
over time.
5. DC HiPot Test
A DC HiPot test is performed using a test voltage that is substantially higher
than the Megohm Test, but, once again, based on operating voltage of the motor
and the appropriate standards/company guidelines. Look for unusually high
leakage currents or a leakage current that doesn’t stay constant or intermittently
jumps up and down. Breakdowns or high leakage currents are an indication of
damaged ground wall insulation. Inspect the motor’s slot liner, wedges,
conductors between the junction box and the coils, etc.
6. Surge Test
A Surge test is performed on each phase of the motor, again using an
appropriate test voltage based on the operating voltage of the machine and the
appropriate standards/company guidelines. Look for a jump to the left of the
surge waveform pattern as the test voltage is increased. This is the signature of
the turn – to – turn short. If a jump is observed, an inspection of the motor
should be made to look for damaged insulation between adjacent conductors.
The insulation may be hard to see visibly, so the motor may have to be
disassembled to find the problem. If no jump in the wave patterns is observed,
the likelihood of motor failure due to insulation failure is greatly reduced
.