WEG W22Xdb C 315 - Page 42

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42
The insulation resistance shall be measured using a Megohmmeter. The test voltage
for the motors winding shall be according the table below in accordance with the
standard IEEE43
Winding rated voltage (V)
Insulation resistance test
direct voltage (V)
< 1000
500
1000 – 2500
500-1000
2501 – 5000
1000 – 2500
5001 - 12000
2500 – 5000
> 12000
5000 – 10000
These measurements shall be made before connecting the supply cables.
A possible diagram to measure the insulation resistance for complete winding is
showed below. The measure must be taken 1 minute after apply the DC voltage with
the insulation tester.
According to standard IEEE 43 the recommended minimum insulation resistance
values at 40ºC in MΩ are the following:
 5 MΩ, for low voltage motors (U < 1,1kV)
 100 MΩ, for medium voltage motors (1,1kV < U < 11kV)
Insulation resistance depends mainly from the winding temperature as showed in the
following table:
WINDING TEMPERATURE
SERVICE VOLTAGE
< 1,1 kV
> 1,1kV
Insulation tester