Frequently Asked Questions & Answers
Temperature Rise
Question: How does the motor insulation system class relate to the winding temperature rise?
Answer: According to NEMA MG1 12.15-16, the winding temperature rise above the temperature of the cooling medium (ambient temperature), shall not exceed the values given in the following table (Table 3). See also "Class ‘B’ vs. Class ‘F’ Insulation".
Table 3: Average Winding Temperature Rise
(Based on maximum ambient temperature of 40° C; Temperatures given in Degrees C)
Insulation Class |
A |
B |
F |
H |
Motors with 1.0 service factor other than those listed below |
60 |
80 |
105 |
125 |
All motors with 1.15 or higher service factor |
70 |
90 |
115 |
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Totally-enclosed non-ventilated motors with 1.0 service factor |
65 |
85 |
110 |
130 |
Motors with encapsulated windings and with 1.0 service factor, all enclosures |
65 |
85 |
110 |
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