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Assembly
5.3 Preparing for installation
Limit values for the winding insulation resistance
The following table specifies the measuring voltage and limit values for the insulation
resistance. These values correspond to the recommendations of IEC 60034-27-4 and
IEEE 43‑2000.
Table 5-1
U
rated
U
meas
R
= minimum insulation resistance at a reference temperature of 40 °C
C
Conversion to the reference temperature
When measuring at winding temperatures other than 40 °C, convert the measured value to the
reference temperature of 40 °C according to the following equations from IEC 60034-27-4 and
IEEE 43‑2000.
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.
44
Insulation resistance of the winding at 40 °C
U
N
V
U ≤ 1000
1000 ≤ U ≤ 2500
2500 < U ≤ 5000
5000 < U ≤ 12000
U > 12000
= rated voltage, see the rating plate
= DC measuring voltage
R
C
R
= K
· R
K
C
T
T
T
R
T
40
10
K
= (0.5)
(40-T)/10
T
T
U
500 (max. 1000)
1000 (max. 2500)
2500 (max. 5000)
5000 (max. 10000)
Insulation resistance converted to 40 °C reference temperature
Temperature coefficient, see below
Measured insulation resistance for measuring/winding temperature T
in °C
Reference temperature in °C
Halving/doubling of the insulation resistance with 10 K
Measuring/winding temperature in °C
meas
V
500
Operating Instructions, 07/2020, A5E46712792A
R
C
MΩ
≥ 5
100
1FU9
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