Table 5-1 Stator Winding Insulation Resistance At 40° C - Siemens 1LA8 Operating Instructions Manual

3. Measure the winding temperature and the insulation resistance of the winding in relation
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
Conversion to the reference temperature
When measuring with winding temperatures other than 40° C, convert the measuring value to
the reference temperature of 40° C according to the following equations from IEEE 43-2000.
(1)
(2)
In this case, doubling or halving the insulation resistance at a temperature change of 10 K is
used as the basis.
● The insulation resistance halves every time the temperature rises by 10 K.
● The resistance doubles every time the temperature falls by 10 K.
SIMOTICS TN Series N-compact 1LA8
Operating Instructions 05/2016
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.
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
R
k
R = K · R
R
C T T
40
10
K = (0.5)
(40-T)/10 T
T
500 (max. 1000)
1000 (max. 2500)
2500 (max. 5000)
5000 (max. 10000)
Insulation resistance converted to 40° C reference temperature
C
Temperature coefficient according to equation (2)
T
Measured insulation resistance for measuring/winding temperature T
T
in °C
Reference temperature in °C
Halving/doubling of the insulation resistance with 10 K
Measuring/winding temperature in °C
5.1 Preparations for installation
V [V]
Meas
500
Assembly
R [MΩ]
C
≥ 5
100
43