Siemens SIMOTICS A-1FV5 Operating Instructions Manual page 46

Commissioning
7.3 Checking the insulation resistance
● Always measure the insulation resistance of the winding to the motor enclosure when the
winding temperature is between 20 and 30 °C.
● When performing the measurement, wait until the final resistance value is reached
(this takes approx. one minute).
Limits
The table below specifies the measuring circuit voltage as well as the limit values for the
minimum insulation resistance and the critical insulation resistance with a rated motor
voltage of U
Table 7- 1
Measurement voltage
Minimum insulation resistance for new, cleaned or repaired
windings
Critical specific insulation resistance after a long operating
time
Note the following:
● Dry, new windings have an insulation resistance of between 100 and 2000 MΩ
(sometimes higher).
An insulation resistance value close to the minimum value could be due to moisture
and/or dirt accumulation.
● The insulation resistance of the motor winding can drop during the course of its service
life can drop due to ambient and operational influences. The critical insulation resistance
for a temperature of 25 °C on the winding can be calculated by multiplying the rated
voltage (kV) by the specific critical resistance value (0.5 MΩ/kV);
Example: Critical resistance for a rated voltage (V
0.6 kV x 0.5 MΩ/kV = 0.3 MΩ
Note
Cleaning and/or drying the windings when reaching critical insulation resistance
If the critical insulation resistance is less than or equal to this value, the windings must be
dried or, if the fan is removed, cleaned thoroughly and dried.
Note that the insulation resistance of dried, clean windings is lower than that of warm
windings. The insulation resistance can only be evaluated accurately when measured on
a winding that has been cooled down to room temperature (approx. 20 to 30 °C).
Note
Measured value close to critical value
If the measured value is close to the critical value, the insulation resistance should be
subsequently checked at suitably regular intervals.
Values apply for measurement at a winding temperature of 25 °C.
46
< 2 kV:
N
Stator winding insulation resistance at 25 °C
Rated voltage U
1000 V (minimum, 100 V)
10 MΩ
0.5 MΩ/kV
) of 0.6 kV:
N
SIMOTICS A-1FV5/1PV5 synchronous/induction motors
Operating Instructions, 03/2014, 610.45002.40
< 2 kV
N