Table 5-1 Stator Winding Insulation Resistance At - Siemens SIMOTICS M-1PH8 Operating Instructions & Installation Instructions

3. Measure the insulation resistance of the winding in relation to the machine housing and the
4. Read out the insulation resistance 1 minute after applying the measuring voltage.
Measuring the polarization index
1. To determine the polarization index, measure the insulation resistances after 1 minute and
2. Express the measured values as a ratio:
Limit values for insulation resistance and polarization index of the stator winding
The following table indicates the measuring voltage and limit values for the insulation
resistance and PI. These values correspond to recommendations in IEEE 43‑2000. In addition,
a critical insulation resistance is specified for the stator winding, which is the minimum
requirement for further operation e.g. following a long-term machine downtime.
Table 5-1 Stator winding insulation resistance at 40℃
U
rated
[V]
U ≤ 1000
1000 ≤ U ≤ 2500
2500 < U ≤ 5000
5000 < U ≤ 12000
U > 12000
U = rated voltage, see the rating plate
rated
U = DC measuring voltage
meas
R = critical or minimum insulation resistance at reference temperature of 40°C
C
R = minimum insulation resistance after cleaning/repair at 40°C
C
R = critical insulation resistance during operation at 40°C
C, operation
R = insulation resistance converted to current measuring/winding temperature
T
PI = polarization index R
insul 10 min
T = current measuring/winding temperature
SIMOTICS M-1PH8
Operating Instructions 05/2012 A5E03986435A AA
winding temperature. The winding temperature should not exceed 40°C during the
measurement. Convert the measured insulation resistances to the reference temperature
of 40°C according to the formula in the following table. This thereby ensures that the
minimum values specified can be compared.
10 minutes.
PI = R / R
insul 10 min insul 1 min
Modern measuring devices display these values automatically following the measurement.
U
meas
[V]
500
500 (max. 1000)
1000 (max. 2500)
2500 (max. 5000)
5000 (max. 10000)
/ R (T < 40°C)
insul 1 min.
5.2 Testing the insulation resistance and polarization index
R R
C C, operation
[MΩ] [MΩ]
≥ 5 0.2 MΩ/kV
(≈0.5 MΩ/kV at 25°C)
100 1.8 MΩ/kV
(≈5 MΩ/kV at 25°C)
Assembling
R PI
T
[MΩ]
2.0
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