Siemens SIMOTICS XP 1MB1 series - Testing the Insulation Resistance and Polarization Index

Assembly
5.1 Preparing for installation
1LA5/6/7/9, 1LG4/6, 1MA6/7, 1MB..1/2/3/4/5 - SH 63 ... 355
Operating Instructions, 06/2018, A5E44455710A
53
5.1.2.2
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. Short-circuit the ends of the temperature sensor cables before applying the test voltage. If
the test voltage is connected to only one temperature sensor terminal, the temperature
sensor will be destroyed.
3. Make sure that no power cables are connected.
4. 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.
5. 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
U
N
V
U
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 a reference temperature of 40 °C