Commissioning
4.3 Checking the insulation resistance
A5E01083943A AB
Siemens AG Operating Instructions 2.02 1FW4
61
CAUTION
Checking of the insulation resistance is required
The insulation resistance needs to be checked prior to startup of the motor and again after
any extended periods of storage or periods during which the motor is not in operation.
Before you begin measuring the insulation resistance, please read the manual for the
insulation resistance meter you are going to use. Disconnect any connected main circuit
cables from the terminals before measuring the insulation resistance.
Measure the insulation resistance of the winding to the motor housing when the winding
temperature is between 20 and 30°C. Other values for the insulation resistance apply at
different temperatures. When measuring, wait until the final resistance value is reached. This
is the case after approx. 1 minute.
Limit values for stator winding
The following table indicates the measuring circuit voltage and the limit values for the
minimum insulation resistance and the critical insulation resistance.
Table 4-1 Insulation resistance at 25°C
Rated voltage
U
N
< 2 kV
Rated voltage
U
N
≥ 2 kV
Measuring circuit voltage 500 V 500 V
Minimum insulation resistance with
new, cleaned or repaired windings
10 MΩ 100 MΩ
Critical specific insulation
resistance after long operating
period
0.5 MΩ/kV 5 MΩ/kV
Note the following points:
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