Siemens SIMOTICS XP 1LA5 Compact Operating Instructions page 29

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
V [V]
N
U ≤ 1000
1000 ≤ U ≤ 2500
2500 < U ≤ 5000
5000 < U ≤ 12000
U > 12000
U = rated voltage, see the rating plate
rated
U = DC measuring voltage
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)
R = K · R
C T T
(2)
K = (0.5)
(40-T)/10
T
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.
For a winding temperature of approx. 25° C, the minimum insulation resistances are
20 MΩ (U ≤ 1000 V) or 300 MΩ (U > 1000 V). The values apply for the complete
winding to ground. Twice the minimum values apply to the measurement of individual
assemblies.
Explosion-protected machines
56100000002002, 01/2016
R Insulation resistance converted to 40° C reference tem-
C
perature
k Temperature coefficient according to equation (2)
T
R Measured insulation resistance for measuring/winding
T
temperature T in °C
40 Reference temperature in °C
10 Halving/doubling of the insulation resistance with 10 K
T Measuring/winding temperature in °C
V [V]
Meas
500
500 (max. 1000)
1000 (max. 2500)
2500 (max. 5000)
5000 (max. 10000)
Installation
R [MΩ]
C
≥ 5
100
101