Limit values for the winding insulation resistance
The following table lists the measuring voltage and limit values for the insulation resistance R
i
.
These values correspond to recommendations provided in IEC 60034-27-4.
Table 5-1
Insulation resistance of the winding at 40 °C
U
rated
/
V
U
meas
/
V
R
iC
/
MΩ
U ≤ 1000
500
≥ 5
1000 ≤ U ≤ 2500
500, max. 1000
100
2500 < U ≤ 5000
1000, max. 2500
5000 < U ≤ 12000
2500, max. 5000
U > 12000
5000, max. 10000
U
rated
= rated voltage, see the rating plate
U
meas
= DC measuring voltage
R
iC
= minimum insulation resistance up to 40 °C winding temperature
Converting to the reference temperature according to IEC 60034-27-4
Convert values measured at winding temperatures of 40 to 60 °C to the reference temperature
of 40 °C:
R
iC
=
R
iT
x
K
T
R
iC
= R
i
converted to the reference temperature of 40 °C
R
iT
= R
i
at the given winding temperature T in °C
K
T
= temperature correction factor
K
T
= 0,5
40 - T
X
X = 1 in the range 10 ... 40 °C
X = 17 in the range 40 ... 60 °C
40 = reference temperature in °C
T = measurement/winding temperature in °C
The values apply for the complete winding to ground. Twice the minimum values apply to the
measurement of individual assemblies.
• Dry, new windings have an insulation resistance of between 100 ... 2000 MΩ, or possibly
even higher values. An insulation resistance value close to the minimum value could be due
to moisture and/or dirt accumulation. The size of the winding, the rated voltage and other
characteristics influence the insulation resistance, and may need to be taken into account
when determining measures.
• Over its operating lifetime, the motor winding insulation resistance can drop due to ambient
and operational influences.
– Calculate the critical insulation resistance value depending on the rated voltage by
multiplying the rated voltage (kV) by the specific critical resistance value.
– Convert the value for the current winding temperature at the time of measurement, see
above table.
Assembly
5.2 Preparing for installation
1LE5, 1PC4 shaft heights 280 ... 355
Operating Instructions, 11/2022, A5E41454666A
53
