Frequently Asked Questions & Answers
Motor Frame Surface Temperatures
Question: What is considered an average motor frame surface temperature?
Answer: Table 3 gives average winding temperature rises for various motors. Frame surface temperatures are typically 15 - 20 degrees centigrade less than the average winding temperature, depending on the size and type of motor along with standard manufacturing variation. For example, a motor designated class F with a 1.15 service factor has an allowable average winding temperature rise of 115 degrees centigrade. This motor has a total temperature of 155 degrees centigrade with the inclusion of the 40 degrees centigrade maximum allowable ambient temperature. Therefore, this motor frame surface temperature could reach 135 - 140 degrees centigrade, as affected by ambient and load conditions.
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