5.1.3 Testing the insulation resistance and polarization index
WARNING
Hazardous voltage at the terminals
During and immediately after measuring the insulation resistance or the polarization index
(PI) of the stator winding, hazardous voltages may be present at some of the terminals.
Contact with these can result in death, serious injury or material damage.
● If any power cables are connected, check to make sure line supply voltage cannot be
delivered.
● Discharge the winding after measurement until the risk is eliminated, e.g. using the
following measures:
– Connect the terminals with the ground potential until the recharge voltage drops to a
non-hazardous level
– Attach the connection cable.
Measure the insulation resistance
1. Before you begin measuring the insulation resistance, please read the operating manual
for the insulation resistance meter you are going to use.
2. Make sure that no power cables are connected.
3. Measure the winding temperature and the insulation resistance of the winding in relation
to the machine enclosure. The winding temperature should not exceed 40° C during the
measurement. Convert the measured insulation resistances in accordance with the formula
to the reference temperature of 40° C. This thereby ensures that the minimum values
specified can be compared.
4. Read out the insulation resistance one minute after applying the measuring voltage.
Limit values for the stator winding insulation resistance
The following table specifies the measuring voltage and limit values for the insulation
resistance. These values correspond to IEEE 43‑2000 recommendations.
Table 5-1 Stator winding insulation resistance at 40° C
V
N
[V] V
Meas
[V] R
C
[MΩ]
U ≤ 1000 500 ≥ 5
1000 ≤ U ≤ 2500 500 (max. 1000) 100
2500 < U ≤ 5000 1000 (max. 2500)
5000 < U ≤ 12000 2500 (max. 5000)
U > 12000 5000 (max. 10000)
U
rated
= rated voltage, see the rating plate
U
meas
= DC measuring voltage
R
C
= minimum insulation resistance at reference temperature of 40° C
Assembly
5.1 Preparations for installation
SIMOTICS TN Series N-compact 1LH8
Operating Instructions 06/2017 45
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