ABB AMA Manual page 76

Manual for High Voltage Process Performance Motors
62 - Maintenance
Figure 7-2 Correlation between the insulation resistance and the temperature
R = Insulation resistance value at a specific temperature
R40 = Equivalent insulation resistance at 40°C
R40 = k x R
Example:
R = 30 MΩ measured at 20°C
k = 0.25
R40 = 0.25 x 30 MΩ = 7.5 MΩ
Table 7-4. Temperature values in degrees Celsius (ºC) and degrees Fahrenheit (ºF)
°C 0 10 20
°F 32 50 68
30 40 50 60
86 104 122 140 158 176 194 212 230
70 80 90 100 110
3BFP 000 063 R0101 REV D