Siemens SIMOTICS XP Operating Instructions Manual page 57

Limit values for the winding insulation resistance
The following table lists the measuring voltage and limit values for the insulation resistance
R . These values correspond to recommendations provided in IEC 60034-27-4.
i
Table 5- 1
U
rated
U
meas
R = minimum insulation resistance up to 40 °C winding temperature
iC
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:
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 affect 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
– Convert the value for the current winding temperature at the time of measurement,
1MB..5/6 shaft height 71 ... 355
Operating Instructions, 10/2021, A5E41926185A
Insulation resistance of the winding at 40 °C
U / V
rated
U ≤ 1000
1000 ≤ U ≤ 2500
2500 < U ≤ 5000
5000 < U ≤ 12000
U > 12000
= rated voltage, see the rating plate
= DC measuring voltage
R = R converted to the reference temperature of 40 °C
iC i
R = R at the given winding temperature T in °C
iT i
K = temperature correction factor
T
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
multiplying the rated voltage (kV) by the specific critical resistance value.
see above table.
5.2 Preparations for installation
U / V
meas
500
500, max. 1000
1000, max. 2500
2500, max. 5000
5000, max. 10000
Assembly
R / MΩ
iC
≥ 5
100
55