Seepex BN 5-12 Series, Operation & Maintenance Manual

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Manual of Electric Motors 76
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The insulation resistance must be measured with a megohmmeter. The machine must be in cold state and
disconnected from the power supply.
The reading of the insulation resistance must be corrected to 40 °C as shown in the Table 5.4.
It is recommended to insulate and test each phase separately. This procedure allows the comparison of the
insulation resistance between each phase. During the test of one phase, the other phases must be grounded.
The test of all phases simultaneously evaluates the insulation resistance to ground only but does not evaluate
the insulation resistance between the phases.
The power supply cables, switches, capacitors and other external devices connected to the motor may
considerably influence the insulation resistance measurement. Thus all external devices must be disconnected
and grounded during the insulation resistance measurement.
Measure the insulation resistance one minute after the voltage has been applied to the winding. The applied
voltage should be as shown in Table 5.3.
Table 5.3 - Voltage for the insulation resistance
Table 5.4 - Correction factor for the insulation resistance corrected to 40 °C
To prevent the risk of an electrical shock, ground the terminals before and after each measurement.
Ground the capacitor (if any) to ensure that it is fully discharged before the measurement is taken.
Winding rated voltage (V) Testing voltage for measuring the insulation resistance (V)
< 1000 500
1000 - 2500 500 - 1000
2501 - 5000 1000 - 2500
5001 - 12000 2500 - 5000
> 12000 5000 - 10000
Measuring temperature
of the insulation
resistance (°C)
Correction factor of the
insulation resistance
corrected to 40 °C
10 0.125
11 0.134
12 0.144
13 0.154
14 0.165
15 0.177
16 0.189
17 0.203
18 0.218
19 0.233
20 0.250
21 0.268
22 0.287
23 0.308
24 0.330
25 0.354
26 0.379
27 0.406
28 0.435
29 0.467
30 0.500
Measuring temperature of
the insulation resistance
(°C)
Correction factor of the
insulation resistance
corrected to 40 °C
30 0.500
31 0.536
32 0.574
33 0.616
34 0.660
35 0.707
36 0.758
37 0.812
38 0.871
39 0.933
40 1.000
41 1.072
42 1.149
43 1.231
44 1.320
45 1.414
46 1.516
47 1.625
48 1.741
49 1.866
50 2.000
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