Testing The Insulation Resistance And Polarization Index - Siemens 1LA8 Operating Instructions Manual

5.1.3

Testing the insulation resistance and polarization index

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
● Discharge the winding after measurement until the risk is eliminated, e.g. using the
Measure the insulation resistance
1. Before you begin measuring the insulation resistance, please read the manual for the
2. Make sure that no power cables are connected.
3. Measure the insulation resistance of the winding in relation to the machine enclosure and
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
U
rated
U
meas
R = minimum insulation resistance at reference temperature of 40° C
C
SIMOTICS TN Series N-compact 1LA8
Operating Instructions 05/2014
WARNING
delivered.
following measures:
– Connecting the terminals with ground potential until the recharge voltage drops to a
non-hazardous level
– Connecting the connecting cable
insulation resistance meter you are going to use.
the 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.
Stator winding insulation resistance at 40° C
V [V]
N
U ≤ 1000
1000 ≤ U ≤ 2500
2500 < U ≤ 5000
5000 < U ≤ 12000
U > 12000
= rated voltage, see the rating plate
= DC measuring voltage
5.1 Preparations for installation
V [V]
Meas
500
500 (max. 1000)
1000 (max. 2500)
2500 (max. 5000)
5000 (max. 10000)
Assembly
R [MΩ]
C
≥ 5
100
45